From b56dd13adddb1d0018e00bd0ea0c3b1a45c719c6 Mon Sep 17 00:00:00 2001
From: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
Date: Sat, 4 May 2024 18:45:55 +0200
Subject: [PATCH] build: remove extern "C" linkage

No more C source files, no more necessity to use C-linkage.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
---
 CODINGSTYLE.md                     |   1 -
 core/android.cpp                   |   3 -
 core/checkcloudconnection.cpp      |   2 +-
 core/deco.cpp                      |  34 ++++----
 core/deco.h                        |   4 -
 core/device.cpp                    |  52 ++++++------
 core/device.h                      |   4 -
 core/dive.cpp                      | 130 ++++++++++++++---------------
 core/dive.h                        |   3 -
 core/divecomputer.cpp              |  60 +++++++------
 core/divecomputer.h                |   4 -
 core/divelist.cpp                  |  40 +++++----
 core/divelist.h                    |   4 -
 core/divelog.cpp                   |   2 +-
 core/divelog.h                     |   4 -
 core/equipment.cpp                 |  54 ++++++------
 core/equipment.h                   |   4 -
 core/errorhelper.h                 |   4 -
 core/event.h                       |   4 -
 core/eventtype.cpp                 |  14 ++--
 core/eventtype.h                   |   9 +-
 core/file.cpp                      |   4 +-
 core/file.h                        |   7 +-
 core/filterconstraint.cpp          |  36 ++++----
 core/filterconstraint.h            |   4 -
 core/filterpreset.cpp              |  16 ++--
 core/filterpreset.h                |   5 --
 core/fulltext.cpp                  |   4 -
 core/fulltext.h                    |  12 +--
 core/gas.h                         |   4 -
 core/gettext.h                     |   2 +-
 core/gettextfromc.cpp              |   2 +-
 core/gettextfromc.h                |   2 +-
 core/git-access.cpp                |  12 +--
 core/git-access.h                  |   4 -
 core/import-cobalt.cpp             |   2 +-
 core/import-csv.cpp                |   2 +-
 core/import-csv.h                  |   4 -
 core/import-divinglog.cpp          |   2 +-
 core/import-seac.cpp               |   2 +-
 core/import-shearwater.cpp         |   4 +-
 core/import-suunto.cpp             |   4 +-
 core/ios.cpp                       |   3 -
 core/libdivecomputer.h             |   4 -
 core/load-git.cpp                  |   4 +-
 core/macos.cpp                     |   4 -
 core/membuffer.h                   |   4 -
 core/metadata.cpp                  |   4 +-
 core/metadata.h                    |   4 -
 core/ostctools.cpp                 |   2 +-
 core/owning_ptrs.h                 |   4 +-
 core/parse-xml.cpp                 |  10 +--
 core/parse.cpp                     |  10 +--
 core/parse.h                       |   3 -
 core/picture.h                     |   4 -
 core/planner.cpp                   |  16 ++--
 core/planner.h                     |   4 -
 core/plannernotes.cpp              |   4 +-
 core/pref.cpp                      |   4 +-
 core/pref.h                        |   4 -
 core/profile.cpp                   |   2 +-
 core/qt-ble.cpp                    |   4 -
 core/qt-ble.h                      |   3 -
 core/qthelper.cpp                  |  22 ++---
 core/qthelper.h                    |  28 ++-----
 core/qtserialbluetooth.cpp         |   3 -
 core/sample.cpp                    |   2 +-
 core/sample.h                      |   4 -
 core/save-git.cpp                  |   4 +-
 core/save-html.h                   |   5 --
 core/save-profiledata.h            |   3 -
 core/save-xml.cpp                  |  10 +--
 core/selection.cpp                 |  18 ++--
 core/selection.h                   |  14 +---
 core/ssrf.h                        |   4 -
 core/strtod.cpp                    |   4 +-
 core/subsurface-string.h           |   4 -
 core/subsurface-time.h             |   5 --
 core/subsurfacestartup.cpp         |   8 +-
 core/subsurfacestartup.h           |   4 -
 core/subsurfacesysinfo.cpp         |   2 +-
 core/subsurfacesysinfo.h           |   4 -
 core/tag.cpp                       |  12 +--
 core/tag.h                         |   9 +-
 core/time.cpp                      |  10 +--
 core/trip.h                        |   4 -
 core/units.cpp                     |  18 ++--
 core/units.h                       |   3 -
 core/unix.cpp                      |   4 -
 core/version.cpp                   |   4 +-
 core/version.h                     |   4 -
 core/webservice.h                  |   4 -
 core/windows.cpp                   |   4 -
 core/windowtitleupdate.cpp         |   2 +-
 core/worldmap-save.cpp             |   2 +-
 core/worldmap-save.h               |   4 -
 core/xmlparams.cpp                 |  18 ++--
 core/xmlparams.h                   |   4 -
 desktop-widgets/mainwindow.cpp     |   4 +-
 desktop-widgets/profilewidget.h    |   2 -
 mobile-widgets/qmlmanager.cpp      |   4 +-
 smtk-import/smartrak.cpp           |   2 +-
 smtk-import/smrtk2ssrfc_window.cpp |   2 +-
 smtk-import/smrtk2ssrfc_window.h   |   2 +-
 104 files changed, 364 insertions(+), 577 deletions(-)

diff --git a/CODINGSTYLE.md b/CODINGSTYLE.md
index 884c0cfbd..909c0e467 100644
--- a/CODINGSTYLE.md
+++ b/CODINGSTYLE.md
@@ -401,7 +401,6 @@ close to our coding standards.
 filetype plugin indent on
 filetype detect
 set cindent tabstop=8 shiftwidth=8 cinoptions=l1,:0,(0,g0
-" TODO: extern "C" gets indented
 
 " And some sane defaults, optional, but quite nice
 set nocompatible
diff --git a/core/android.cpp b/core/android.cpp
index a8a0dd0e9..fef58a48c 100644
--- a/core/android.cpp
+++ b/core/android.cpp
@@ -41,8 +41,6 @@ static std::string make_default_filename()
 	return system_default_path() + "/subsurface.xml";
 }
 
-extern "C" {
-
 const char android_system_divelist_default_font[] = "Roboto";
 const char *system_divelist_default_font = android_system_divelist_default_font;
 double system_divelist_default_font_size = -1;
@@ -251,7 +249,6 @@ bool subsurface_user_is_root()
 {
 	return false;
 }
-}
 
 /* called from QML manager */
 void checkPendingIntents()
diff --git a/core/checkcloudconnection.cpp b/core/checkcloudconnection.cpp
index 384afdb3d..ff180ddf9 100644
--- a/core/checkcloudconnection.cpp
+++ b/core/checkcloudconnection.cpp
@@ -200,7 +200,7 @@ void CheckCloudConnection::gotContinent(QNetworkReply *reply)
 }
 
 // helper to be used from C code
-extern "C" bool canReachCloudServer(struct git_info *info)
+bool canReachCloudServer(struct git_info *info)
 {
 	if (verbose)
 		qWarning() << "Cloud storage: checking connection to cloud server" << info->url.c_str();
diff --git a/core/deco.cpp b/core/deco.cpp
index eb4d4308a..7c8b6bdee 100644
--- a/core/deco.cpp
+++ b/core/deco.cpp
@@ -216,7 +216,7 @@ static double vpmb_tolerated_ambient_pressure(struct deco_state *ds, double refe
 	return ds->tissue_n2_sat[ci] + ds->tissue_he_sat[ci] + vpmb_config.other_gases_pressure - total_gradient;
 }
 
-extern "C" double tissue_tolerance_calc(struct deco_state *ds, const struct dive *dive, double pressure, bool in_planner)
+double tissue_tolerance_calc(struct deco_state *ds, const struct dive *dive, double pressure, bool in_planner)
 {
 	int ci = -1;
 	double ret_tolerance_limit_ambient_pressure = 0.0;
@@ -323,7 +323,7 @@ static double calc_surface_phase(double surface_pressure, double he_pressure, do
 	return 0;
 }
 
-extern "C" void vpmb_start_gradient(struct deco_state *ds)
+void vpmb_start_gradient(struct deco_state *ds)
 {
 	int ci;
 
@@ -333,7 +333,7 @@ extern "C" void vpmb_start_gradient(struct deco_state *ds)
 	}
 }
 
-extern "C" void vpmb_next_gradient(struct deco_state *ds, double deco_time, double surface_pressure, bool in_planner)
+void vpmb_next_gradient(struct deco_state *ds, double deco_time, double surface_pressure, bool in_planner)
 {
 	int ci;
 	double n2_b, n2_c;
@@ -379,7 +379,7 @@ static double solve_cubic(double A, double B, double C)
 }
 
 
-extern "C" void nuclear_regeneration(struct deco_state *ds, double time)
+void nuclear_regeneration(struct deco_state *ds, double time)
 {
 	time /= 60.0;
 	int ci;
@@ -411,7 +411,7 @@ static double calc_inner_pressure(double crit_radius, double onset_tension, doub
 }
 
 // Calculates the crushing pressure in the given moment. Updates crushing_onset_tension and critical radius if needed
-extern "C" void calc_crushing_pressure(struct deco_state *ds, double pressure)
+void calc_crushing_pressure(struct deco_state *ds, double pressure)
 {
 	int ci;
 	double gradient;
@@ -443,7 +443,7 @@ extern "C" void calc_crushing_pressure(struct deco_state *ds, double pressure)
 }
 
 /* add period_in_seconds at the given pressure and gas to the deco calculation */
-extern "C" void add_segment(struct deco_state *ds, double pressure, struct gasmix gasmix, int period_in_seconds, int ccpo2, enum divemode_t divemode, int, bool in_planner)
+void add_segment(struct deco_state *ds, double pressure, struct gasmix gasmix, int period_in_seconds, int ccpo2, enum divemode_t divemode, int, bool in_planner)
 {
 	int ci;
 	struct gas_pressures pressures;
@@ -476,7 +476,7 @@ extern "C" void add_segment(struct deco_state *ds, double pressure, struct gasmi
 }
 
 #if DECO_CALC_DEBUG
-extern "C" void dump_tissues(struct deco_state *ds)
+void dump_tissues(struct deco_state *ds)
 {
 	int ci;
 	printf("N2 tissues:");
@@ -489,7 +489,7 @@ extern "C" void dump_tissues(struct deco_state *ds)
 }
 #endif
 
-extern "C" void clear_vpmb_state(struct deco_state *ds)
+void clear_vpmb_state(struct deco_state *ds)
 {
 	int ci;
 	for (ci = 0; ci < 16; ci++) {
@@ -501,7 +501,7 @@ extern "C" void clear_vpmb_state(struct deco_state *ds)
 	ds->max_bottom_ceiling_pressure.mbar = 0;
 }
 
-extern "C" void clear_deco(struct deco_state *ds, double surface_pressure, bool in_planner)
+void clear_deco(struct deco_state *ds, double surface_pressure, bool in_planner)
 {
 	int ci;
 
@@ -545,7 +545,7 @@ void deco_state_cache::restore(struct deco_state *target, bool keep_vpmb_state)
 	*target = *data;
 }
 
-extern "C" int deco_allowed_depth(double tissues_tolerance, double surface_pressure, const struct dive *dive, bool smooth)
+int deco_allowed_depth(double tissues_tolerance, double surface_pressure, const struct dive *dive, bool smooth)
 {
 	int depth;
 	double pressure_delta;
@@ -564,7 +564,7 @@ extern "C" int deco_allowed_depth(double tissues_tolerance, double surface_press
 	return depth;
 }
 
-extern "C" void set_gf(short gflow, short gfhigh)
+void set_gf(short gflow, short gfhigh)
 {
 	if (gflow != -1)
 		buehlmann_config.gf_low = (double)gflow / 100.0;
@@ -572,7 +572,7 @@ extern "C" void set_gf(short gflow, short gfhigh)
 		buehlmann_config.gf_high = (double)gfhigh / 100.0;
 }
 
-extern "C" void set_vpmb_conservatism(short conservatism)
+void set_vpmb_conservatism(short conservatism)
 {
 	if (conservatism < 0)
 		vpmb_config.conservatism = 0;
@@ -582,7 +582,7 @@ extern "C" void set_vpmb_conservatism(short conservatism)
 		vpmb_config.conservatism = conservatism;
 }
 
-extern "C" double get_gf(struct deco_state *ds, double ambpressure_bar, const struct dive *dive)
+double get_gf(struct deco_state *ds, double ambpressure_bar, const struct dive *dive)
 {
 	double surface_pressure_bar = get_surface_pressure_in_mbar(dive, true) / 1000.0;
 	double gf_low = buehlmann_config.gf_low;
@@ -596,7 +596,7 @@ extern "C" double get_gf(struct deco_state *ds, double ambpressure_bar, const st
 	return gf;
 }
 
-extern "C" double regressiona(const struct deco_state *ds)
+double regressiona(const struct deco_state *ds)
 {
 	if (ds->sum1 > 1) {
 		double avxy = ds->sumxy / ds->sum1;
@@ -609,7 +609,7 @@ extern "C" double regressiona(const struct deco_state *ds)
 		return 0.0;
 }
 
-extern "C" double regressionb(const struct deco_state *ds)
+double regressionb(const struct deco_state *ds)
 {
 	if (ds->sum1)
 		return ds->sumy / ds->sum1 - ds->sumx * regressiona(ds) / ds->sum1;
@@ -617,14 +617,14 @@ extern "C" double regressionb(const struct deco_state *ds)
 		return 0.0;
 }
 
-extern "C" void reset_regression(struct deco_state *ds)
+void reset_regression(struct deco_state *ds)
 {
 	ds->sum1 = 0;
 	ds->sumxx = ds->sumx = 0L;
 	ds->sumy = ds->sumxy = 0.0;
 }
 
-extern "C" void update_regression(struct deco_state *ds, const struct dive *dive)
+void update_regression(struct deco_state *ds, const struct dive *dive)
 {
 	if (!ds->plot_depth)
 		return;
diff --git a/core/deco.h b/core/deco.h
index 5d2dbba06..479f81cb1 100644
--- a/core/deco.h
+++ b/core/deco.h
@@ -7,8 +7,6 @@
 #include "divemode.h"
 #include <memory>
 
-extern "C" {
-
 struct dive;
 struct divecomputer;
 struct decostop;
@@ -69,8 +67,6 @@ extern double regressionb(const struct deco_state *ds);
 extern void reset_regression(struct deco_state *ds);
 extern void update_regression(struct deco_state *ds, const struct dive *dive);
 
-}
-
 struct deco_state_cache {
 	// Test if there is cached data
 	operator bool () {
diff --git a/core/device.cpp b/core/device.cpp
index f72240f6f..9a64cf83d 100644
--- a/core/device.cpp
+++ b/core/device.cpp
@@ -27,7 +27,7 @@ bool device::operator<(const device &a) const
 	return serialNumber < a.serialNumber;
 }
 
-extern "C" const struct device *get_device_for_dc(const struct device_table *table, const struct divecomputer *dc)
+const struct device *get_device_for_dc(const struct device_table *table, const struct divecomputer *dc)
 {
 	if (!dc->model || !dc->serial)
 		return NULL;
@@ -38,7 +38,7 @@ extern "C" const struct device *get_device_for_dc(const struct device_table *tab
 	return it != dcs.end() && same_device(*it, dev) ? &*it : NULL;
 }
 
-extern "C" int get_or_add_device_for_dc(struct device_table *table, const struct divecomputer *dc)
+int get_or_add_device_for_dc(struct device_table *table, const struct divecomputer *dc)
 {
 	if (!dc->model || !dc->serial)
 		return -1;
@@ -50,7 +50,7 @@ extern "C" int get_or_add_device_for_dc(struct device_table *table, const struct
 	return create_device_node(table, dc->model, dc->serial, "");
 }
 
-extern "C" bool device_exists(const struct device_table *device_table, const struct device *dev)
+bool device_exists(const struct device_table *device_table, const struct device *dev)
 {
 	auto it = std::lower_bound(device_table->devices.begin(), device_table->devices.end(), *dev);
 	return it != device_table->devices.end() && same_device(*it, *dev);
@@ -86,17 +86,17 @@ static int addDC(std::vector<device> &dcs, const std::string &m, const std::stri
 	}
 }
 
-extern "C" int create_device_node(struct device_table *device_table, const char *model, const char *serial, const char *nickname)
+int create_device_node(struct device_table *device_table, const char *model, const char *serial, const char *nickname)
 {
 	return addDC(device_table->devices, model ?: "", serial ?: "", nickname ?: "");
 }
 
-extern "C" int add_to_device_table(struct device_table *device_table, const struct device *dev)
+int add_to_device_table(struct device_table *device_table, const struct device *dev)
 {
 	return create_device_node(device_table, dev->model.c_str(), dev->serialNumber.c_str(), dev->nickName.c_str());
 }
 
-extern "C" int remove_device(struct device_table *device_table, const struct device *dev)
+int remove_device(struct device_table *device_table, const struct device *dev)
 {
 	auto it = std::lower_bound(device_table->devices.begin(), device_table->devices.end(), *dev);
 	if (it != device_table->devices.end() && same_device(*it, *dev)) {
@@ -108,20 +108,20 @@ extern "C" int remove_device(struct device_table *device_table, const struct dev
 	}
 }
 
-extern "C" void remove_from_device_table(struct device_table *device_table, int idx)
+void remove_from_device_table(struct device_table *device_table, int idx)
 {
 	if (idx < 0 || idx >= (int)device_table->devices.size())
 		return;
 	device_table->devices.erase(device_table->devices.begin() + idx);
 }
 
-extern "C" void clear_device_table(struct device_table *device_table)
+void clear_device_table(struct device_table *device_table)
 {
 	device_table->devices.clear();
 }
 
 /* Returns whether the given device is used by a selected dive. */
-extern "C" bool device_used_by_selected_dive(const struct device *dev)
+bool device_used_by_selected_dive(const struct device *dev)
 {
 	for (dive *d: getDiveSelection()) {
 		struct divecomputer *dc;
@@ -133,7 +133,7 @@ extern "C" bool device_used_by_selected_dive(const struct device *dev)
 	return false;
 }
 
-extern "C" int is_default_dive_computer_device(const char *name)
+int is_default_dive_computer_device(const char *name)
 {
 	return qPrefDiveComputer::device() == name;
 }
@@ -148,46 +148,46 @@ const char *get_dc_nickname(const struct divecomputer *dc)
 		return dc->model;
 }
 
-extern "C" int nr_devices(const struct device_table *table)
+int nr_devices(const struct device_table *table)
 {
 	return (int)table->devices.size();
 }
 
-extern "C" const struct device *get_device(const struct device_table *table, int i)
+const struct device *get_device(const struct device_table *table, int i)
 {
 	if (i < 0 || i > nr_devices(table))
 		return NULL;
 	return &table->devices[i];
 }
 
-extern "C" struct device *get_device_mutable(struct device_table *table, int i)
+struct device *get_device_mutable(struct device_table *table, int i)
 {
 	if (i < 0 || i > nr_devices(table))
 		return NULL;
 	return &table->devices[i];
 }
 
-extern "C" const char *device_get_model(const struct device *dev)
+const char *device_get_model(const struct device *dev)
 {
 	return dev ? dev->model.c_str() : NULL;
 }
 
-extern "C" const char *device_get_serial(const struct device *dev)
+const char *device_get_serial(const struct device *dev)
 {
 	return dev ? dev->serialNumber.c_str() : NULL;
 }
 
-extern "C" const char *device_get_nickname(const struct device *dev)
+const char *device_get_nickname(const struct device *dev)
 {
 	return dev ? dev->nickName.c_str() : NULL;
 }
 
-extern "C" struct device_table *alloc_device_table()
+struct device_table *alloc_device_table()
 {
 	return new struct device_table;
 }
 
-extern "C" void free_device_table(struct device_table *devices)
+void free_device_table(struct device_table *devices)
 {
 	delete devices;
 }
@@ -202,7 +202,7 @@ bool fingerprint_record::operator<(const fingerprint_record &a) const
 
 // annoyingly, the Cressi Edy doesn't support a serial number (it's always 0), but still uses fingerprints
 // so we can't bail on the serial number being 0
-extern "C" unsigned int get_fingerprint_data(const struct fingerprint_table *table, uint32_t model, uint32_t serial, const unsigned char **fp_out)
+unsigned int get_fingerprint_data(const struct fingerprint_table *table, uint32_t model, uint32_t serial, const unsigned char **fp_out)
 {
 	if (model == 0 || fp_out == nullptr)
 		return 0;
@@ -219,7 +219,7 @@ extern "C" unsigned int get_fingerprint_data(const struct fingerprint_table *tab
 	return 0;
 }
 
-extern "C" void create_fingerprint_node(struct fingerprint_table *table, uint32_t model, uint32_t serial,
+void create_fingerprint_node(struct fingerprint_table *table, uint32_t model, uint32_t serial,
 				       const unsigned char *raw_data_in, unsigned int fsize, uint32_t fdeviceid, uint32_t fdiveid)
 {
 	// since raw data can contain \0 we copy this manually, not as string
@@ -245,7 +245,7 @@ extern "C" void create_fingerprint_node(struct fingerprint_table *table, uint32_
 	}
 }
 
-extern "C" void create_fingerprint_node_from_hex(struct fingerprint_table *table, uint32_t model, uint32_t serial,
+void create_fingerprint_node_from_hex(struct fingerprint_table *table, uint32_t model, uint32_t serial,
 						const char *hex_data, uint32_t fdeviceid, uint32_t fdiveid)
 {
 	QByteArray raw = QByteArray::fromHex(hex_data);
@@ -253,33 +253,33 @@ extern "C" void create_fingerprint_node_from_hex(struct fingerprint_table *table
 				(const unsigned char *)raw.constData(), raw.size(), fdeviceid, fdiveid);
 }
 
-extern "C" int nr_fingerprints(struct fingerprint_table *table)
+int nr_fingerprints(struct fingerprint_table *table)
 {
 	return table->fingerprints.size();
 }
 
-extern "C" uint32_t fp_get_model(struct fingerprint_table *table, unsigned int i)
+uint32_t fp_get_model(struct fingerprint_table *table, unsigned int i)
 {
 	if (!table || i >= table->fingerprints.size())
 		return 0;
 	return table->fingerprints[i].model;
 }
 
-extern "C" uint32_t fp_get_serial(struct fingerprint_table *table, unsigned int i)
+uint32_t fp_get_serial(struct fingerprint_table *table, unsigned int i)
 {
 	if (!table || i >= table->fingerprints.size())
 		return 0;
 	return table->fingerprints[i].serial;
 }
 
-extern "C" uint32_t fp_get_deviceid(struct fingerprint_table *table, unsigned int i)
+uint32_t fp_get_deviceid(struct fingerprint_table *table, unsigned int i)
 {
 	if (!table || i >= table->fingerprints.size())
 		return 0;
 	return table->fingerprints[i].fdeviceid;
 }
 
-extern "C" uint32_t fp_get_diveid(struct fingerprint_table *table, unsigned int i)
+uint32_t fp_get_diveid(struct fingerprint_table *table, unsigned int i)
 {
 	if (!table || i >= table->fingerprints.size())
 		return 0;
diff --git a/core/device.h b/core/device.h
index 1d9b4210e..5c9f042b1 100644
--- a/core/device.h
+++ b/core/device.h
@@ -6,8 +6,6 @@
 #include <string>
 #include <vector>
 
-extern "C" {
-
 struct divecomputer;
 struct device;
 struct device_table;
@@ -61,8 +59,6 @@ typedef void (*device_callback_t)(const char *name, void *userdata);
 
 extern int enumerate_devices(device_callback_t callback, void *userdata, unsigned int transport);
 
-}
-
 // Functions and global variables that are only available to C++ code
 struct device {
 	bool operator<(const device &a) const;
diff --git a/core/dive.cpp b/core/dive.cpp
index 888f92ef5..80a441dfb 100644
--- a/core/dive.cpp
+++ b/core/dive.cpp
@@ -51,7 +51,7 @@ static double calculate_depth_to_mbarf(int depth, pressure_t surface_pressure, i
  * This function returns a negative number for "no legacy mode",
  * or a non-negative number that indicates the o2 sensor index.
  */
-extern "C" int legacy_format_o2pressures(const struct dive *dive, const struct divecomputer *dc)
+int legacy_format_o2pressures(const struct dive *dive, const struct divecomputer *dc)
 {
 	int i, o2sensor;
 
@@ -83,7 +83,7 @@ extern "C" int legacy_format_o2pressures(const struct dive *dive, const struct d
 }
 
 /* warning: does not test idx for validity */
-extern "C" struct event *create_gas_switch_event(struct dive *dive, struct divecomputer *dc, int seconds, int idx)
+struct event *create_gas_switch_event(struct dive *dive, struct divecomputer *dc, int seconds, int idx)
 {
 	/* The gas switch event format is insane for historical reasons */
 	struct gasmix mix = get_cylinder(dive, idx)->gasmix;
@@ -102,7 +102,7 @@ extern "C" struct event *create_gas_switch_event(struct dive *dive, struct divec
 	return ev;
 }
 
-extern "C" void add_gas_switch_event(struct dive *dive, struct divecomputer *dc, int seconds, int idx)
+void add_gas_switch_event(struct dive *dive, struct divecomputer *dc, int seconds, int idx)
 {
 	/* sanity check so we don't crash */
 	/* FIXME: The planner uses a dummy cylinder one past the official number of cylinders
@@ -120,7 +120,7 @@ extern "C" void add_gas_switch_event(struct dive *dive, struct divecomputer *dc,
  * have to actually remove the existing event and replace it with a new one.
  * WARNING, WARNING... this may end up freeing event in case that event is indeed
  * WARNING, WARNING... part of this divecomputer on this dive! */
-extern "C" void update_event_name(struct dive *d, int dc_number, struct event *event, const char *name)
+void update_event_name(struct dive *d, int dc_number, struct event *event, const char *name)
 {
 	if (!d || !event)
 		return;
@@ -140,7 +140,7 @@ extern "C" void update_event_name(struct dive *d, int dc_number, struct event *e
 	invalidate_dive_cache(d);
 }
 
-extern "C" struct gasmix get_gasmix_from_event(const struct dive *dive, const struct event *ev)
+struct gasmix get_gasmix_from_event(const struct dive *dive, const struct event *ev)
 {
 	if (ev && event_is_gaschange(ev)) {
 		int index = ev->gas.index;
@@ -156,14 +156,14 @@ extern "C" struct gasmix get_gasmix_from_event(const struct dive *dive, const st
 
 // we need this to be uniq. oh, and it has no meaning whatsoever
 // - that's why we have the silly initial number and increment by 3 :-)
-extern "C" int dive_getUniqID()
+int dive_getUniqID()
 {
 	static int maxId = 83529;
 	maxId += 3;
 	return maxId;
 }
 
-extern "C" struct dive *alloc_dive(void)
+struct dive *alloc_dive(void)
 {
 	struct dive *dive;
 
@@ -235,7 +235,7 @@ static void free_dive_structures(struct dive *d)
 	free(d->pictures.pictures);
 }
 
-extern "C" void free_dive(struct dive *d)
+void free_dive(struct dive *d)
 {
 	free_dive_structures(d);
 	free(d);
@@ -245,7 +245,7 @@ extern "C" void free_dive(struct dive *d)
  * in order not to leak memory, we need to free those .
  * copy_dive doesn't play with the divetrip and forward/backward pointers
  * so we can ignore those */
-extern "C" void clear_dive(struct dive *d)
+void clear_dive(struct dive *d)
 {
 	if (!d)
 		return;
@@ -278,7 +278,7 @@ static void copy_dive_nodc(const struct dive *s, struct dive *d)
 	d->tag_list = taglist_copy(s->tag_list);
 }
 
-extern "C" void copy_dive(const struct dive *s, struct dive *d)
+void copy_dive(const struct dive *s, struct dive *d)
 {
 	copy_dive_nodc(s, d);
 
@@ -297,7 +297,7 @@ static void copy_dive_onedc(const struct dive *s, const struct divecomputer *sdc
 /* make a clone of the source dive and clean out the source dive;
  * this allows us to create a dive on the stack and then
  * add it to the divelist. */
-extern "C" struct dive *move_dive(struct dive *s)
+struct dive *move_dive(struct dive *s)
 {
 	struct dive *dive = alloc_dive();
 	*dive = *s;			   // so all the pointers in dive point to the things s pointed to
@@ -310,7 +310,7 @@ extern "C" struct dive *move_dive(struct dive *s)
 		d->_component = copy_string(s->_component)
 
 // copy elements, depending on bits in what that are set
-extern "C" void selective_copy_dive(const struct dive *s, struct dive *d, struct dive_components what, bool clear)
+void selective_copy_dive(const struct dive *s, struct dive *d, struct dive_components what, bool clear)
 {
 	if (clear)
 		clear_dive(d);
@@ -342,7 +342,7 @@ extern "C" void selective_copy_dive(const struct dive *s, struct dive *d, struct
 /* copies all events from the given dive computer before a given time
    this is used when editing a dive in the planner to preserve the events
    of the old dive */
-extern "C" void copy_events_until(const struct dive *sd, struct dive *dd, int dcNr, int time)
+void copy_events_until(const struct dive *sd, struct dive *dd, int dcNr, int time)
 {
 	if (!sd || !dd)
 		return;
@@ -363,17 +363,17 @@ extern "C" void copy_events_until(const struct dive *sd, struct dive *dd, int dc
 	}
 }
 
-extern "C" int nr_cylinders(const struct dive *dive)
+int nr_cylinders(const struct dive *dive)
 {
 	return dive->cylinders.nr;
 }
 
-extern "C" int nr_weightsystems(const struct dive *dive)
+int nr_weightsystems(const struct dive *dive)
 {
 	return dive->weightsystems.nr;
 }
 
-extern "C" void copy_used_cylinders(const struct dive *s, struct dive *d, bool used_only)
+void copy_used_cylinders(const struct dive *s, struct dive *d, bool used_only)
 {
 	int i;
 	if (!s || !d)
@@ -488,7 +488,7 @@ static bool has_unknown_used_cylinders(const struct dive *dive, const struct div
 	return num > 0;
 }
 
-extern "C" void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, int *mean, int *duration)
+void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, int *mean, int *duration)
 {
 	int i;
 	int32_t lasttime = 0;
@@ -597,7 +597,7 @@ static int same_rounded_pressure(pressure_t a, pressure_t b)
  * first cylinder - in which case cylinder 0 is indeed the first cylinder.
  * We likewise return 0 if the event concerns a cylinder that doesn't exist.
  * If the dive has no cylinders, -1 is returned. */
-extern "C" int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *dc)
+int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *dc)
 {
 	int res = 0;
 	if (!dive->cylinders.nr)
@@ -615,7 +615,7 @@ extern "C" int explicit_first_cylinder(const struct dive *dive, const struct div
 /* this gets called when the dive mode has changed (so OC vs. CC)
  * there are two places we might have setpoints... events or in the samples
  */
-extern "C" void update_setpoint_events(const struct dive *dive, struct divecomputer *dc)
+void update_setpoint_events(const struct dive *dive, struct divecomputer *dc)
 {
 	struct event *ev;
 	int new_setpoint = 0;
@@ -775,7 +775,7 @@ static struct event *find_previous_event(struct divecomputer *dc, struct event *
 	return previous;
 }
 
-extern "C" pressure_t calculate_surface_pressure(const struct dive *dive)
+pressure_t calculate_surface_pressure(const struct dive *dive)
 {
 	const struct divecomputer *dc;
 	pressure_t res;
@@ -799,7 +799,7 @@ static void fixup_surface_pressure(struct dive *dive)
 /* if the surface pressure in the dive data is redundant to the calculated
  * value (i.e., it was added by running fixup on the dive) return 0,
  * otherwise return the surface pressure given in the dive */
-extern "C" pressure_t un_fixup_surface_pressure(const struct dive *d)
+pressure_t un_fixup_surface_pressure(const struct dive *d)
 {
 	pressure_t res = d->surface_pressure;
 	if (res.mbar && res.mbar == calculate_surface_pressure(d).mbar)
@@ -824,7 +824,7 @@ static void fixup_water_salinity(struct dive *dive)
 		dive->salinity = (sum + nr / 2) / nr;
 }
 
-extern "C" int get_dive_salinity(const struct dive *dive)
+int get_dive_salinity(const struct dive *dive)
 {
 	return dive->user_salinity ? dive->user_salinity : dive->salinity;
 }
@@ -1263,7 +1263,7 @@ static void fixup_dive_dc(struct dive *dive, struct divecomputer *dc)
 		fake_dc(dc);
 }
 
-extern "C" struct dive *fixup_dive(struct dive *dive)
+struct dive *fixup_dive(struct dive *dive)
 {
 	int i;
 	struct divecomputer *dc;
@@ -1653,7 +1653,7 @@ pick_b:
  * A negative number returned indicates that a match could not be found.
  * Call parameters: dive = the dive being processed
  *                  cylinder_use_type = an enum, one of {oxygen, diluent, bailout} */
-extern "C" int get_cylinder_idx_by_use(const struct dive *dive, enum cylinderuse cylinder_use_type)
+int get_cylinder_idx_by_use(const struct dive *dive, enum cylinderuse cylinder_use_type)
 {
 	int cylinder_index;
 	for (cylinder_index = 0; cylinder_index < dive->cylinders.nr; cylinder_index++) {
@@ -1750,14 +1750,14 @@ static void dc_cylinder_renumber(struct dive *dive, struct divecomputer *dc, con
  * Also note that we assume that the initial cylinder is cylinder 0,
  * so if that got renamed, we need to create a fake gas change event
  */
-extern "C" void cylinder_renumber(struct dive *dive, int mapping[])
+void cylinder_renumber(struct dive *dive, int mapping[])
 {
 	struct divecomputer *dc;
 	for_each_dc (dive, dc)
 		dc_cylinder_renumber(dive, dc, mapping);
 }
 
-extern "C" int same_gasmix_cylinder(const cylinder_t *cyl, int cylid, const struct dive *dive, bool check_unused)
+int same_gasmix_cylinder(const cylinder_t *cyl, int cylid, const struct dive *dive, bool check_unused)
 {
 	struct gasmix mygas = cyl->gasmix;
 	for (int i = 0; i < dive->cylinders.nr; i++) {
@@ -2352,7 +2352,7 @@ static int likely_same_dive(const struct dive *a, const struct dive *b)
  * Attn: The dive_site parameter of the dive will be set, but the caller
  * still has to register the dive in the dive site!
  */
-extern "C" struct dive *try_to_merge(struct dive *a, struct dive *b, bool prefer_downloaded)
+struct dive *try_to_merge(struct dive *a, struct dive *b, bool prefer_downloaded)
 {
 	struct dive *res;
 	struct dive_site *site;
@@ -2562,12 +2562,12 @@ static bool has_dc_type(const struct dive *dive, bool dc_is_planner)
 }
 
 // Does this dive have a dive computer for which is_dc_planner has value planned
-extern "C" bool is_planned(const struct dive *dive)
+bool is_planned(const struct dive *dive)
 {
 	return has_dc_type(dive, true);
 }
 
-extern "C" bool is_logged(const struct dive *dive)
+bool is_logged(const struct dive *dive)
 {
 	return has_dc_type(dive, false);
 }
@@ -2601,7 +2601,7 @@ extern "C" bool is_logged(const struct dive *dive)
  * The dive site the new dive should be added to (if any) is returned
  * in the "dive_site" output parameter.
  */
-extern "C" struct dive *merge_dives(const struct dive *a, const struct dive *b, int offset, bool prefer_downloaded, struct dive_trip **trip, struct dive_site **site)
+struct dive *merge_dives(const struct dive *a, const struct dive *b, int offset, bool prefer_downloaded, struct dive_trip **trip, struct dive_site **site)
 {
 	struct dive *res = alloc_dive();
 
@@ -2871,7 +2871,7 @@ static bool should_split(const struct divecomputer *dc, int t1, int t2)
  *
  * In other words, this is a (simplified) reversal of the dive merging.
  */
-extern "C" int split_dive(const struct dive *dive, struct dive **new1, struct dive **new2)
+int split_dive(const struct dive *dive, struct dive **new1, struct dive **new2)
 {
 	int i;
 	int at_surface, surface_start;
@@ -2914,7 +2914,7 @@ extern "C" int split_dive(const struct dive *dive, struct dive **new1, struct di
 	return -1;
 }
 
-extern "C" int split_dive_at_time(const struct dive *dive, duration_t time, struct dive **new1, struct dive **new2)
+int split_dive_at_time(const struct dive *dive, duration_t time, struct dive **new1, struct dive **new2)
 {
 	int i = 0;
 
@@ -2977,12 +2977,12 @@ static inline int dive_totaltime(const struct dive *dive)
 	return time;
 }
 
-extern "C" timestamp_t dive_endtime(const struct dive *dive)
+timestamp_t dive_endtime(const struct dive *dive)
 {
 	return dive->when + dive_totaltime(dive);
 }
 
-extern "C" bool time_during_dive_with_offset(const struct dive *dive, timestamp_t when, timestamp_t offset)
+bool time_during_dive_with_offset(const struct dive *dive, timestamp_t when, timestamp_t offset)
 {
 	timestamp_t start = dive->when;
 	timestamp_t end = dive_endtime(dive);
@@ -2999,7 +2999,7 @@ extern "C" bool time_during_dive_with_offset(const struct dive *dive, timestamp_
  * functionality for the core library that Subsurface itself doesn't
  * use but that another consumer of the library (like an HTML exporter)
  * will need */
-extern "C" void set_informational_units(const char *units)
+void set_informational_units(const char *units)
 {
 	if (strstr(units, "METRIC")) {
 		git_prefs.unit_system = METRIC;
@@ -3035,7 +3035,7 @@ extern "C" void set_informational_units(const char *units)
 
 }
 
-extern "C" void set_git_prefs(const char *prefs)
+void set_git_prefs(const char *prefs)
 {
 	if (strstr(prefs, "TANKBAR"))
 		git_prefs.tankbar = 1;
@@ -3048,7 +3048,7 @@ extern "C" void set_git_prefs(const char *prefs)
 }
 
 /* clones a dive and moves given dive computer to front */
-extern "C" struct dive *make_first_dc(const struct dive *d, int dc_number)
+struct dive *make_first_dc(const struct dive *d, int dc_number)
 {
 	struct dive *res;
 	struct divecomputer *dc, *newdc, *old_dc;
@@ -3112,7 +3112,7 @@ static void delete_divecomputer(struct dive *d, int num)
 }
 
 /* Clone a dive and delete goven dive computer */
-extern "C" struct dive *clone_delete_divecomputer(const struct dive *d, int dc_number)
+struct dive *clone_delete_divecomputer(const struct dive *d, int dc_number)
 {
 	struct dive *res;
 
@@ -3135,7 +3135,7 @@ extern "C" struct dive *clone_delete_divecomputer(const struct dive *d, int dc_n
  * The dives will not be associated with a trip.
  * On error, both output parameters are set to NULL.
  */
-extern "C" void split_divecomputer(const struct dive *src, int num, struct dive **out1, struct dive **out2)
+void split_divecomputer(const struct dive *src, int num, struct dive **out1, struct dive **out2)
 {
 	const struct divecomputer *srcdc = get_dive_dc_const(src, num);
 
@@ -3161,7 +3161,7 @@ extern "C" void split_divecomputer(const struct dive *src, int num, struct dive
 }
 
 //Calculate O2 in best mix
-extern "C" fraction_t best_o2(depth_t depth, const struct dive *dive, bool in_planner)
+fraction_t best_o2(depth_t depth, const struct dive *dive, bool in_planner)
 {
 	fraction_t fo2;
 	int po2 = in_planner ? prefs.bottompo2 : (int)(prefs.modpO2 * 1000.0);
@@ -3174,7 +3174,7 @@ extern "C" fraction_t best_o2(depth_t depth, const struct dive *dive, bool in_pl
 }
 
 //Calculate He in best mix. O2 is considered narcopic
-extern "C" fraction_t best_he(depth_t depth, const struct dive *dive, bool o2narcotic, fraction_t fo2)
+fraction_t best_he(depth_t depth, const struct dive *dive, bool o2narcotic, fraction_t fo2)
 {
 	fraction_t fhe;
 	int pnarcotic, ambient;
@@ -3190,18 +3190,18 @@ extern "C" fraction_t best_he(depth_t depth, const struct dive *dive, bool o2nar
 	return fhe;
 }
 
-extern "C" void invalidate_dive_cache(struct dive *dive)
+void invalidate_dive_cache(struct dive *dive)
 {
 	memset(dive->git_id, 0, 20);
 }
 
-extern "C" bool dive_cache_is_valid(const struct dive *dive)
+bool dive_cache_is_valid(const struct dive *dive)
 {
 	static const unsigned char null_id[20] = { 0, };
 	return !!memcmp(dive->git_id, null_id, 20);
 }
 
-extern "C" int get_surface_pressure_in_mbar(const struct dive *dive, bool non_null)
+int get_surface_pressure_in_mbar(const struct dive *dive, bool non_null)
 {
 	int mbar = dive->surface_pressure.mbar;
 	if (!mbar && non_null)
@@ -3237,12 +3237,12 @@ static double calculate_depth_to_mbarf(int depth, pressure_t surface_pressure, i
 	return mbar + depth * specific_weight;
 }
 
-extern "C" int depth_to_mbar(int depth, const struct dive *dive)
+int depth_to_mbar(int depth, const struct dive *dive)
 {
 	return lrint(depth_to_mbarf(depth, dive));
 }
 
-extern "C" double depth_to_mbarf(int depth, const struct dive *dive)
+double depth_to_mbarf(int depth, const struct dive *dive)
 {
 	// For downloaded and planned dives, use DC's values
 	int salinity = dive->dc.salinity;
@@ -3255,12 +3255,12 @@ extern "C" double depth_to_mbarf(int depth, const struct dive *dive)
 	return calculate_depth_to_mbarf(depth, surface_pressure, salinity);
 }
 
-extern "C" double depth_to_bar(int depth, const struct dive *dive)
+double depth_to_bar(int depth, const struct dive *dive)
 {
 	return depth_to_mbar(depth, dive) / 1000.0;
 }
 
-extern "C" double depth_to_atm(int depth, const struct dive *dive)
+double depth_to_atm(int depth, const struct dive *dive)
 {
 	return mbar_to_atm(depth_to_mbar(depth, dive));
 }
@@ -3269,7 +3269,7 @@ extern "C" double depth_to_atm(int depth, const struct dive *dive)
  * (that's the one that some dive computers like the Uemis Zurich
  * provide - for the other models that do this libdivecomputer has to
  * take care of this, but the Uemis we support natively */
-extern "C" int rel_mbar_to_depth(int mbar, const struct dive *dive)
+int rel_mbar_to_depth(int mbar, const struct dive *dive)
 {
 	// For downloaded and planned dives, use DC's salinity. Manual dives, use user's salinity
 	int salinity = is_dc_manually_added_dive(&dive->dc) ? dive->user_salinity : dive->dc.salinity;
@@ -3281,7 +3281,7 @@ extern "C" int rel_mbar_to_depth(int mbar, const struct dive *dive)
 	return (int)lrint(mbar / specific_weight);
 }
 
-extern "C" int mbar_to_depth(int mbar, const struct dive *dive)
+int mbar_to_depth(int mbar, const struct dive *dive)
 {
 	// For downloaded and planned dives, use DC's pressure. Manual dives, use user's pressure
 	pressure_t surface_pressure = is_dc_manually_added_dive(&dive->dc)
@@ -3295,7 +3295,7 @@ extern "C" int mbar_to_depth(int mbar, const struct dive *dive)
 }
 
 /* MOD rounded to multiples of roundto mm */
-extern "C" depth_t gas_mod(struct gasmix mix, pressure_t po2_limit, const struct dive *dive, int roundto)
+depth_t gas_mod(struct gasmix mix, pressure_t po2_limit, const struct dive *dive, int roundto)
 {
 	depth_t rounded_depth;
 
@@ -3305,7 +3305,7 @@ extern "C" depth_t gas_mod(struct gasmix mix, pressure_t po2_limit, const struct
 }
 
 /* Maximum narcotic depth rounded to multiples of roundto mm */
-extern "C" depth_t gas_mnd(struct gasmix mix, depth_t end, const struct dive *dive, int roundto)
+depth_t gas_mnd(struct gasmix mix, depth_t end, const struct dive *dive, int roundto)
 {
 	depth_t rounded_depth;
 	pressure_t ppo2n2;
@@ -3323,14 +3323,14 @@ extern "C" depth_t gas_mnd(struct gasmix mix, depth_t end, const struct dive *di
 	return rounded_depth;
 }
 
-extern "C" struct dive *get_dive(int nr)
+struct dive *get_dive(int nr)
 {
 	if (nr >= divelog.dives->nr || nr < 0)
 		return NULL;
 	return divelog.dives->dives[nr];
 }
 
-extern "C" struct dive_site *get_dive_site_for_dive(const struct dive *dive)
+struct dive_site *get_dive_site_for_dive(const struct dive *dive)
 {
 	return dive->dive_site;
 }
@@ -3347,7 +3347,7 @@ std::string get_dive_location(const struct dive *dive)
 	return ds ? ds->name : std::string();
 }
 
-extern "C" unsigned int number_of_computers(const struct dive *dive)
+unsigned int number_of_computers(const struct dive *dive)
 {
 	unsigned int total_number = 0;
 	const struct divecomputer *dc = &dive->dc;
@@ -3362,7 +3362,7 @@ extern "C" unsigned int number_of_computers(const struct dive *dive)
 	return total_number;
 }
 
-extern "C" struct divecomputer *get_dive_dc(struct dive *dive, int nr)
+struct divecomputer *get_dive_dc(struct dive *dive, int nr)
 {
 	struct divecomputer *dc;
 	if (!dive)
@@ -3377,12 +3377,12 @@ extern "C" struct divecomputer *get_dive_dc(struct dive *dive, int nr)
 	return dc;
 }
 
-extern "C" const struct divecomputer *get_dive_dc_const(const struct dive *dive, int nr)
+const struct divecomputer *get_dive_dc_const(const struct dive *dive, int nr)
 {
 	return get_dive_dc((struct dive *)dive, nr);
 }
 
-extern "C" struct dive *get_dive_by_uniq_id(int id)
+struct dive *get_dive_by_uniq_id(int id)
 {
 	int i;
 	struct dive *dive = NULL;
@@ -3400,7 +3400,7 @@ extern "C" struct dive *get_dive_by_uniq_id(int id)
 	return dive;
 }
 
-extern "C" int get_idx_by_uniq_id(int id)
+int get_idx_by_uniq_id(int id)
 {
 	int i;
 	struct dive *dive = NULL;
@@ -3418,12 +3418,12 @@ extern "C" int get_idx_by_uniq_id(int id)
 	return i;
 }
 
-extern "C" bool dive_site_has_gps_location(const struct dive_site *ds)
+bool dive_site_has_gps_location(const struct dive_site *ds)
 {
 	return ds && has_location(&ds->location);
 }
 
-extern "C" int dive_has_gps_location(const struct dive *dive)
+int dive_has_gps_location(const struct dive *dive)
 {
 	if (!dive)
 		return false;
@@ -3458,7 +3458,7 @@ static location_t dc_get_gps_location(const struct divecomputer *dc)
  * This function is potentially slow, therefore only call sparingly
  * and remember the result.
  */
-extern "C" location_t dive_get_gps_location(const struct dive *d)
+location_t dive_get_gps_location(const struct dive *d)
 {
 	location_t res = { };
 
@@ -3478,7 +3478,7 @@ extern "C" location_t dive_get_gps_location(const struct dive *d)
 }
 
 /* When evaluated at the time of a gasswitch, this returns the new gas */
-extern "C" struct gasmix get_gasmix(const struct dive *dive, const struct divecomputer *dc, int time, const struct event **evp, struct gasmix gasmix)
+struct gasmix get_gasmix(const struct dive *dive, const struct divecomputer *dc, int time, const struct event **evp, struct gasmix gasmix)
 {
 	const struct event *ev = *evp;
 	struct gasmix res;
@@ -3506,7 +3506,7 @@ extern "C" struct gasmix get_gasmix(const struct dive *dive, const struct diveco
 
 /* get the gas at a certain time during the dive */
 /* If there is a gasswitch at that time, it returns the new gasmix */
-extern "C" struct gasmix get_gasmix_at_time(const struct dive *d, const struct divecomputer *dc, duration_t time)
+struct gasmix get_gasmix_at_time(const struct dive *d, const struct divecomputer *dc, duration_t time)
 {
 	const struct event *ev = NULL;
 	struct gasmix gasmix = gasmix_air;
@@ -3514,7 +3514,7 @@ extern "C" struct gasmix get_gasmix_at_time(const struct dive *d, const struct d
 }
 
 /* Does that cylinder have any pressure readings? */
-extern "C" bool cylinder_with_sensor_sample(const struct dive *dive, int cylinder_id)
+bool cylinder_with_sensor_sample(const struct dive *dive, int cylinder_id)
 {
 	for (const struct divecomputer *dc = &dive->dc; dc; dc = dc->next) {
 		for (int i = 0; i < dc->samples; ++i) {
diff --git a/core/dive.h b/core/dive.h
index e78214282..1c8696110 100644
--- a/core/dive.h
+++ b/core/dive.h
@@ -13,8 +13,6 @@
 #include <stdlib.h>
 #include <string>
 
-extern "C" {
-
 extern int last_xml_version;
 
 extern const char *divemode_text_ui[];
@@ -218,7 +216,6 @@ extern struct gasmix get_gasmix(const struct dive *dive, const struct divecomput
 extern struct gasmix get_gasmix_at_time(const struct dive *dive, const struct divecomputer *dc, duration_t time);
 
 extern void update_setpoint_events(const struct dive *dive, struct divecomputer *dc);
-}
 
 /* Make pointers to dive and dive_trip "Qt metatypes" so that they can be passed through
  * QVariants and through QML.
diff --git a/core/divecomputer.cpp b/core/divecomputer.cpp
index 4577baf39..61a90fbfb 100644
--- a/core/divecomputer.cpp
+++ b/core/divecomputer.cpp
@@ -117,7 +117,7 @@ static void fill_samples_no_avg(struct sample *s, int max_d, int max_t, double s
 	}
 }
 
-extern "C" void fake_dc(struct divecomputer *dc)
+void fake_dc(struct divecomputer *dc)
 {
 	alloc_samples(dc, 6);
 	struct sample *fake = dc->sample;
@@ -199,7 +199,7 @@ extern "C" void fake_dc(struct divecomputer *dc)
  * saving the dive mode for each event. When the events occur AFTER 'time' seconds, the last stored divemode
  * is returned. This function is self-tracking, relying on setting the event pointer 'evp' so that, in each iteration
  * that calls this function, the search does not have to begin at the first event of the dive */
-extern "C" enum divemode_t get_current_divemode(const struct divecomputer *dc, int time, const struct event **evp, enum divemode_t *divemode)
+enum divemode_t get_current_divemode(const struct divecomputer *dc, int time, const struct event **evp, enum divemode_t *divemode)
 {
 	const struct event *ev = *evp;
 	if (dc) {
@@ -221,7 +221,7 @@ extern "C" enum divemode_t get_current_divemode(const struct divecomputer *dc, i
 
 /* helper function to make it easier to work with our structures
  * we don't interpolate here, just use the value from the last sample up to that time */
-extern "C" int get_depth_at_time(const struct divecomputer *dc, unsigned int time)
+int get_depth_at_time(const struct divecomputer *dc, unsigned int time)
 {
 	int depth = 0;
 	if (dc && dc->sample)
@@ -236,7 +236,7 @@ extern "C" int get_depth_at_time(const struct divecomputer *dc, unsigned int tim
 
 /* The first divecomputer is embedded in the dive structure. Free its data but not
  * the structure itself. For all remainding dcs in the list, free data *and* structures. */
-extern "C" void free_dive_dcs(struct divecomputer *dc)
+void free_dive_dcs(struct divecomputer *dc)
 {
 	free_dc_contents(dc);
 	STRUCTURED_LIST_FREE(struct divecomputer, dc->next, free_dc);
@@ -244,7 +244,7 @@ extern "C" void free_dive_dcs(struct divecomputer *dc)
 
 /* make room for num samples; if not enough space is available, the sample
  * array is reallocated and the existing samples are copied. */
-extern "C" void alloc_samples(struct divecomputer *dc, int num)
+void alloc_samples(struct divecomputer *dc, int num)
 {
 	if (num > dc->alloc_samples) {
 		dc->alloc_samples = (num * 3) / 2 + 10;
@@ -254,7 +254,7 @@ extern "C" void alloc_samples(struct divecomputer *dc, int num)
 	}
 }
 
-extern "C" void free_samples(struct divecomputer *dc)
+void free_samples(struct divecomputer *dc)
 {
 	if (dc) {
 		free(dc->sample);
@@ -264,7 +264,7 @@ extern "C" void free_samples(struct divecomputer *dc)
 	}
 }
 
-extern "C" struct sample *prepare_sample(struct divecomputer *dc)
+struct sample *prepare_sample(struct divecomputer *dc)
 {
 	if (dc) {
 		int nr = dc->samples;
@@ -291,12 +291,12 @@ extern "C" struct sample *prepare_sample(struct divecomputer *dc)
 }
 
 
-extern "C" void finish_sample(struct divecomputer *dc)
+void finish_sample(struct divecomputer *dc)
 {
 	dc->samples++;
 }
 
-extern "C" struct sample *add_sample(const struct sample *sample, int time, struct divecomputer *dc)
+struct sample *add_sample(const struct sample *sample, int time, struct divecomputer *dc)
 {
 	struct sample *p = prepare_sample(dc);
 
@@ -314,7 +314,7 @@ extern "C" struct sample *add_sample(const struct sample *sample, int time, stru
  *
  * This ignores any surface time in the middle of the dive.
  */
-extern "C" void fixup_dc_duration(struct divecomputer *dc)
+void fixup_dc_duration(struct divecomputer *dc)
 {
 	int duration, i;
 	int lasttime, lastdepth, depthtime;
@@ -347,7 +347,7 @@ extern "C" void fixup_dc_duration(struct divecomputer *dc)
  * What do the dive computers say the water temperature is?
  * (not in the samples, but as dc property for dcs that support that)
  */
-extern "C" unsigned int dc_watertemp(const struct divecomputer *dc)
+unsigned int dc_watertemp(const struct divecomputer *dc)
 {
 	int sum = 0, nr = 0;
 
@@ -365,7 +365,7 @@ extern "C" unsigned int dc_watertemp(const struct divecomputer *dc)
 /*
  * What do the dive computers say the air temperature is?
  */
-extern "C" unsigned int dc_airtemp(const struct divecomputer *dc)
+unsigned int dc_airtemp(const struct divecomputer *dc)
 {
 	int sum = 0, nr = 0;
 
@@ -381,7 +381,7 @@ extern "C" unsigned int dc_airtemp(const struct divecomputer *dc)
 }
 
 /* copies all events in this dive computer */
-extern "C" void copy_events(const struct divecomputer *s, struct divecomputer *d)
+void copy_events(const struct divecomputer *s, struct divecomputer *d)
 {
 	const struct event *ev;
 	struct event **pev;
@@ -398,7 +398,7 @@ extern "C" void copy_events(const struct divecomputer *s, struct divecomputer *d
 	*pev = NULL;
 }
 
-extern "C" void copy_samples(const struct divecomputer *s, struct divecomputer *d)
+void copy_samples(const struct divecomputer *s, struct divecomputer *d)
 {
 	/* instead of carefully copying them one by one and calling add_sample
 	 * over and over again, let's just copy the whole blob */
@@ -420,7 +420,7 @@ extern "C" void copy_samples(const struct divecomputer *s, struct divecomputer *
 		memcpy(d->sample, s->sample, nr * sizeof(struct sample));
 }
 
-extern "C" void add_event_to_dc(struct divecomputer *dc, struct event *ev)
+void add_event_to_dc(struct divecomputer *dc, struct event *ev)
 {
 	struct event **p;
 
@@ -433,7 +433,7 @@ extern "C" void add_event_to_dc(struct divecomputer *dc, struct event *ev)
 	*p = ev;
 }
 
-extern "C" struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name)
+struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name)
 {
 	struct event *ev = create_event(time, type, flags, value, name);
 
@@ -446,7 +446,7 @@ extern "C" struct event *add_event(struct divecomputer *dc, unsigned int time, i
 }
 
 /* Substitutes an event in a divecomputer for another. No reordering is performed! */
-extern "C" void swap_event(struct divecomputer *dc, struct event *from, struct event *to)
+void swap_event(struct divecomputer *dc, struct event *from, struct event *to)
 {
 	for (struct event **ep = &dc->events; *ep; ep = &(*ep)->next) {
 		if (*ep == from) {
@@ -459,7 +459,7 @@ extern "C" void swap_event(struct divecomputer *dc, struct event *from, struct e
 }
 
 /* Remove given event from dive computer. Does *not* free the event. */
-extern "C" void remove_event_from_dc(struct divecomputer *dc, struct event *event)
+void remove_event_from_dc(struct divecomputer *dc, struct event *event)
 {
 	for (struct event **ep = &dc->events; *ep; ep = &(*ep)->next) {
 		if (*ep == event) {
@@ -470,7 +470,7 @@ extern "C" void remove_event_from_dc(struct divecomputer *dc, struct event *even
 	}
 }
 
-extern "C" void add_extra_data(struct divecomputer *dc, const char *key, const char *value)
+void add_extra_data(struct divecomputer *dc, const char *key, const char *value)
 {
 	struct extra_data **ed = &dc->extra_data;
 
@@ -492,13 +492,21 @@ extern "C" void add_extra_data(struct divecomputer *dc, const char *key, const c
 	}
 }
 
+<<<<<<< HEAD
+=======
+bool is_dc_planner(const struct divecomputer *dc)
+{
+	return same_string(dc->model, "planned dive");
+}
+
+>>>>>>> ed6cdf19f (build: remove extern "C" linkage)
 /*
  * Match two dive computer entries against each other, and
  * tell if it's the same dive. Return 0 if "don't know",
  * positive for "same dive" and negative for "definitely
  * not the same dive"
  */
-extern "C" int match_one_dc(const struct divecomputer *a, const struct divecomputer *b)
+int match_one_dc(const struct divecomputer *a, const struct divecomputer *b)
 {
 	/* Not same model? Don't know if matching.. */
 	if (!a->model || !b->model)
@@ -527,7 +535,7 @@ static void free_extra_data(struct extra_data *ed)
 	free((void *)ed->value);
 }
 
-extern "C" void free_dc_contents(struct divecomputer *dc)
+void free_dc_contents(struct divecomputer *dc)
 {
 	free(dc->sample);
 	free((void *)dc->model);
@@ -537,7 +545,7 @@ extern "C" void free_dc_contents(struct divecomputer *dc)
 	STRUCTURED_LIST_FREE(struct extra_data, dc->extra_data, free_extra_data);
 }
 
-extern "C" void free_dc(struct divecomputer *dc)
+void free_dc(struct divecomputer *dc)
 {
 	free_dc_contents(dc);
 	free(dc);
@@ -545,12 +553,12 @@ extern "C" void free_dc(struct divecomputer *dc)
 
 static const char *planner_dc_name = "planned dive";
 
-extern "C" bool is_dc_planner(const struct divecomputer *dc)
+bool is_dc_planner(const struct divecomputer *dc)
 {
 	return same_string(dc->model, planner_dc_name);
 }
 
-extern "C" void make_planner_dc(struct divecomputer *dc)
+void make_planner_dc(struct divecomputer *dc)
 {
 	free((void *)dc->model);
 	dc->model = strdup(planner_dc_name);
@@ -558,12 +566,12 @@ extern "C" void make_planner_dc(struct divecomputer *dc)
 
 const char *manual_dc_name = "manually added dive";
 
-extern "C" bool is_dc_manually_added_dive(const struct divecomputer *dc)
+bool is_dc_manually_added_dive(const struct divecomputer *dc)
 {
 	return dc && same_string(dc->model, manual_dc_name);
 }
 
-extern "C" void make_manually_added_dive_dc(struct divecomputer *dc)
+void make_manually_added_dive_dc(struct divecomputer *dc)
 {
 	free((void *)dc->model);
 	dc->model = strdup(manual_dc_name);
diff --git a/core/divecomputer.h b/core/divecomputer.h
index d4d0f834a..de7bdfa45 100644
--- a/core/divecomputer.h
+++ b/core/divecomputer.h
@@ -5,8 +5,6 @@
 #include "divemode.h"
 #include "units.h"
 
-extern "C" {
-
 struct extra_data;
 struct sample;
 
@@ -75,6 +73,4 @@ extern void make_manually_added_dive_dc(struct divecomputer *dc);
 /* Check if two dive computer entries are the exact same dive (-1=no/0=maybe/1=yes) */
 extern int match_one_dc(const struct divecomputer *a, const struct divecomputer *b);
 
-}
-
 #endif
diff --git a/core/divelist.cpp b/core/divelist.cpp
index b3f072be9..805345941 100644
--- a/core/divelist.cpp
+++ b/core/divelist.cpp
@@ -29,7 +29,7 @@
  *  - Nitrox trumps air (even if hypoxic)
  * These are the same rules as the inter-dive sorting rules.
  */
-extern "C" void get_dive_gas(const struct dive *dive, int *o2_p, int *he_p, int *o2max_p)
+void get_dive_gas(const struct dive *dive, int *o2_p, int *he_p, int *o2max_p)
 {
 	int i;
 	int maxo2 = -1, maxhe = -1, mino2 = 1000;
@@ -63,7 +63,7 @@ extern "C" void get_dive_gas(const struct dive *dive, int *o2_p, int *he_p, int
 	*o2max_p = maxo2;
 }
 
-extern "C" int total_weight(const struct dive *dive)
+int total_weight(const struct dive *dive)
 {
 	int i, total_grams = 0;
 
@@ -424,7 +424,7 @@ static void add_dive_to_deco(struct deco_state *ds, struct dive *dive, bool in_p
 	}
 }
 
-extern "C" int get_divenr(const struct dive *dive)
+int get_divenr(const struct dive *dive)
 {
 	int i;
 	const struct dive *d;
@@ -442,7 +442,7 @@ extern "C" int get_divenr(const struct dive *dive)
 /* return negative surface time if dives are overlapping */
 /* The place you call this function is likely the place where you want
  * to create the deco_state */
-extern "C" int init_decompression(struct deco_state *ds, const struct dive *dive, bool in_planner)
+int init_decompression(struct deco_state *ds, const struct dive *dive, bool in_planner)
 {
 	int i, divenr = -1;
 	int surface_time = 48 * 60 * 60;
@@ -656,7 +656,7 @@ static int comp_dc(const struct divecomputer *dc1, const struct divecomputer *dc
  * We might also consider sorting by end-time and other criteria,
  * but see the caveat above (editing means rearrangement of the dives).
  */
-extern "C" int comp_dives(const struct dive *a, const struct dive *b)
+int comp_dives(const struct dive *a, const struct dive *b)
 {
 	int cmp;
 	if (a->when < b->when)
@@ -697,7 +697,7 @@ MAKE_REMOVE(dive_table, struct dive *, dive)
 MAKE_CLEAR_TABLE(dive_table, dives, dive)
 MAKE_MOVE_TABLE(dive_table, dives)
 
-extern "C" void insert_dive(struct dive_table *table, struct dive *d)
+void insert_dive(struct dive_table *table, struct dive *d)
 {
 	int idx = dive_table_get_insertion_index(table, d);
 	add_to_dive_table(table, idx, d);
@@ -733,13 +733,13 @@ static void autogroup_dives(struct dive_table *table, struct trip_table *trip_ta
 /* Remove a dive from a dive table. This assumes that the
  * dive was already removed from any trip and deselected.
  * It simply shrinks the table and frees the trip */
-extern "C" void delete_dive_from_table(struct dive_table *table, int idx)
+void delete_dive_from_table(struct dive_table *table, int idx)
 {
 	free_dive(table->dives[idx]);
 	remove_from_dive_table(table, idx);
 }
 
-extern "C" struct dive *get_dive_from_table(int nr, const struct dive_table *dt)
+struct dive *get_dive_from_table(int nr, const struct dive_table *dt)
 {
 	if (nr >= dt->nr || nr < 0)
 		return NULL;
@@ -750,7 +750,7 @@ extern "C" struct dive *get_dive_from_table(int nr, const struct dive_table *dt)
  * resources associated with the dive. The caller must removed the dive
  * from the trip-list. Returns a pointer to the unregistered dive.
  * The unregistered dive has the selection- and hidden-flags cleared. */
-extern "C" struct dive *unregister_dive(int idx)
+struct dive *unregister_dive(int idx)
 {
 	struct dive *dive = get_dive(idx);
 	if (!dive)
@@ -765,7 +765,7 @@ extern "C" struct dive *unregister_dive(int idx)
 	return dive;
 }
 
-extern "C" void process_loaded_dives()
+void process_loaded_dives()
 {
 	sort_dive_table(divelog.dives);
 	sort_trip_table(divelog.trips);
@@ -944,7 +944,7 @@ static bool merge_dive_tables(struct dive_table *dives_from, struct dive_table *
 /* Merge the dives of the trip "from" and the dive_table "dives_from" into the trip "to"
  * and dive_table "dives_to". If "prefer_imported" is true, dive data of "from" takes
  * precedence */
-extern "C" void add_imported_dives(struct divelog *import_log, int flags)
+void add_imported_dives(struct divelog *import_log, int flags)
 {
 	int i, idx;
 	struct dive_table dives_to_add = empty_dive_table;
@@ -1024,7 +1024,6 @@ extern "C" void add_imported_dives(struct divelog *import_log, int flags)
  * Returns true if trip was merged. In this case, the trip will be
  * freed.
  */
-extern "C"
 bool try_to_merge_trip(struct dive_trip *trip_import, struct dive_table *import_table, bool prefer_imported,
 		       /* output parameters: */
 		       struct dive_table *dives_to_add, struct dive_table *dives_to_remove,
@@ -1081,7 +1080,6 @@ bool try_to_merge_trip(struct dive_trip *trip_import, struct dive_table *import_
  * - If IMPORT_ADD_TO_NEW_TRIP is true, dives that are not assigned
  *   to a trip will be added to a newly generated trip.
  */
-extern "C"
 void process_imported_dives(struct divelog *import_log, int flags,
 			    /* output parameters: */
 			    struct dive_table *dives_to_add, struct dive_table *dives_to_remove,
@@ -1249,7 +1247,7 @@ static struct dive *get_last_valid_dive()
  * 	- last_nr+1 for addition at end of log (if last dive had a number)
  * 	- 0 for all other cases
  */
-extern "C" int get_dive_nr_at_idx(int idx)
+int get_dive_nr_at_idx(int idx)
 {
 	if (idx < divelog.dives->nr)
 		return 0;
@@ -1261,12 +1259,12 @@ extern "C" int get_dive_nr_at_idx(int idx)
 
 static int min_datafile_version;
 
-extern "C" int get_min_datafile_version()
+int get_min_datafile_version()
 {
 	return min_datafile_version;
 }
 
-extern "C" void report_datafile_version(int version)
+void report_datafile_version(int version)
 {
 	if (min_datafile_version == 0 || min_datafile_version > version)
 		min_datafile_version = version;
@@ -1291,7 +1289,7 @@ void clear_dive_file_data()
 	emit_reset_signal();
 }
 
-extern "C" bool dive_less_than(const struct dive *a, const struct dive *b)
+bool dive_less_than(const struct dive *a, const struct dive *b)
 {
 	return comp_dives(a, b) < 0;
 }
@@ -1330,7 +1328,7 @@ static int comp_dive_or_trip(struct dive_or_trip a, struct dive_or_trip b)
 		return -comp_dive_to_trip(b.dive, a.trip);
 }
 
-extern "C" bool dive_or_trip_less_than(struct dive_or_trip a, struct dive_or_trip b)
+bool dive_or_trip_less_than(struct dive_or_trip a, struct dive_or_trip b)
 {
 	return comp_dive_or_trip(a, b) < 0;
 }
@@ -1345,7 +1343,7 @@ extern "C" bool dive_or_trip_less_than(struct dive_or_trip a, struct dive_or_tri
  * that happened inside other dives. The interval will always be calculated
  * with respect to the dive that started previously.
  */
-extern "C" timestamp_t get_surface_interval(timestamp_t when)
+timestamp_t get_surface_interval(timestamp_t when)
 {
 	int i;
 	timestamp_t prev_end;
@@ -1366,7 +1364,7 @@ extern "C" timestamp_t get_surface_interval(timestamp_t when)
 
 /* Find visible dive close to given date. First search towards older,
  * then newer dives. */
-extern "C" struct dive *find_next_visible_dive(timestamp_t when)
+struct dive *find_next_visible_dive(timestamp_t when)
 {
 	int i, j;
 
@@ -1392,7 +1390,7 @@ extern "C" struct dive *find_next_visible_dive(timestamp_t when)
 	return NULL;
 }
 
-extern "C" bool has_dive(unsigned int deviceid, unsigned int diveid)
+bool has_dive(unsigned int deviceid, unsigned int diveid)
 {
        int i;
        struct dive *dive;
diff --git a/core/divelist.h b/core/divelist.h
index c46316bf2..fed83f31c 100644
--- a/core/divelist.h
+++ b/core/divelist.h
@@ -4,8 +4,6 @@
 
 #include "units.h"
 
-extern "C" {
-
 struct dive;
 struct divelog;
 struct trip_table;
@@ -60,6 +58,4 @@ void move_dive_table(struct dive_table *src, struct dive_table *dst);
 struct dive *unregister_dive(int idx);
 extern bool has_dive(unsigned int deviceid, unsigned int diveid);
 
-}
-
 #endif // DIVELIST_H
diff --git a/core/divelog.cpp b/core/divelog.cpp
index f5c42b88c..5a4caea23 100644
--- a/core/divelog.cpp
+++ b/core/divelog.cpp
@@ -92,7 +92,7 @@ void divelog::clear()
 	filter_presets->clear();
 }
 
-extern "C" void clear_divelog(struct divelog *log)
+void clear_divelog(struct divelog *log)
 {
 	log->clear();
 }
diff --git a/core/divelog.h b/core/divelog.h
index 44ec950a4..b3612a405 100644
--- a/core/divelog.h
+++ b/core/divelog.h
@@ -27,11 +27,7 @@ struct divelog {
 
 extern struct divelog divelog;
 
-extern "C" {
-
 void clear_divelog(struct divelog *);
 extern void delete_single_dive(struct divelog *, int idx);
 
-}
-
 #endif
diff --git a/core/equipment.cpp b/core/equipment.cpp
index 9dbcfdf49..82f7d5340 100644
--- a/core/equipment.cpp
+++ b/core/equipment.cpp
@@ -25,26 +25,26 @@
  * is freed, but the data it references. The object itself is passed in by value.
  * This is due to the fact how the table macros work.
  */
-extern "C" void free_weightsystem(weightsystem_t ws)
+void free_weightsystem(weightsystem_t ws)
 {
 	free((void *)ws.description);
 	ws.description = NULL;
 }
 
-extern "C" void free_cylinder(cylinder_t c)
+void free_cylinder(cylinder_t c)
 {
 	free((void *)c.type.description);
 	c.type.description = NULL;
 }
 
-extern "C" void copy_weights(const struct weightsystem_table *s, struct weightsystem_table *d)
+void copy_weights(const struct weightsystem_table *s, struct weightsystem_table *d)
 {
 	clear_weightsystem_table(d);
 	for (int i = 0; i < s->nr; i++)
 		add_cloned_weightsystem(d, s->weightsystems[i]);
 }
 
-extern "C" void copy_cylinders(const struct cylinder_table *s, struct cylinder_table *d)
+void copy_cylinders(const struct cylinder_table *s, struct cylinder_table *d)
 {
 	int i;
 	clear_cylinder_table(d);
@@ -76,7 +76,7 @@ const char *cylinderuse_text[NUM_GAS_USE] = {
 	QT_TRANSLATE_NOOP("gettextFromC", "OC-gas"), QT_TRANSLATE_NOOP("gettextFromC", "diluent"), QT_TRANSLATE_NOOP("gettextFromC", "oxygen"), QT_TRANSLATE_NOOP("gettextFromC", "not used")
 };
 
-extern "C" enum cylinderuse cylinderuse_from_text(const char *text)
+enum cylinderuse cylinderuse_from_text(const char *text)
 {
 	for (int i = 0; i < static_cast<int>(NUM_GAS_USE); i++) {
 		if (same_string(text, cylinderuse_text[i]) || same_string(text, translate("gettextFromC", cylinderuse_text[i])))
@@ -178,7 +178,7 @@ weight_t get_weightsystem_weight(const std::string &name)
 	return it != ws_info_table.end() ? it->weight : weight_t();
 }
 
-extern "C" weightsystem_t clone_weightsystem(weightsystem_t ws)
+weightsystem_t clone_weightsystem(weightsystem_t ws)
 {
 	weightsystem_t res = { ws.weight, copy_string(ws.description), ws.auto_filled };
 	return res;
@@ -186,19 +186,19 @@ extern "C" weightsystem_t clone_weightsystem(weightsystem_t ws)
 
 /* Add a clone of a weightsystem to the end of a weightsystem table.
  * Cloned means that the description-string is copied. */
-extern "C" void add_cloned_weightsystem(struct weightsystem_table *t, weightsystem_t ws)
+void add_cloned_weightsystem(struct weightsystem_table *t, weightsystem_t ws)
 {
 	add_to_weightsystem_table(t, t->nr, clone_weightsystem(ws));
 }
 
-extern "C" cylinder_t clone_cylinder(cylinder_t cyl)
+cylinder_t clone_cylinder(cylinder_t cyl)
 {
 	cylinder_t res = cyl;
 	res.type.description = copy_string(res.type.description);
 	return res;
 }
 
-extern "C" void add_cylinder(struct cylinder_table *t, int idx, cylinder_t cyl)
+void add_cylinder(struct cylinder_table *t, int idx, cylinder_t cyl)
 {
 	add_to_cylinder_table(t, idx, cyl);
 	/* FIXME: This is a horrible hack: we make sure that at the end of
@@ -212,18 +212,18 @@ extern "C" void add_cylinder(struct cylinder_table *t, int idx, cylinder_t cyl)
 
 /* Add a clone of a cylinder to the end of a cylinder table.
  * Cloned means that the description-string is copied. */
-extern "C" void add_cloned_cylinder(struct cylinder_table *t, cylinder_t cyl)
+void add_cloned_cylinder(struct cylinder_table *t, cylinder_t cyl)
 {
 	add_cylinder(t, t->nr, clone_cylinder(cyl));
 }
 
-extern "C" bool same_weightsystem(weightsystem_t w1, weightsystem_t w2)
+bool same_weightsystem(weightsystem_t w1, weightsystem_t w2)
 {
 	return w1.weight.grams == w2.weight.grams &&
 	       same_string(w1.description, w2.description);
 }
 
-extern "C" void get_gas_string(struct gasmix gasmix, char *text, int len)
+void get_gas_string(struct gasmix gasmix, char *text, int len)
 {
 	if (gasmix_is_air(gasmix))
 		snprintf(text, len, "%s", translate("gettextFromC", "air"));
@@ -236,21 +236,21 @@ extern "C" void get_gas_string(struct gasmix gasmix, char *text, int len)
 }
 
 /* Returns a static char buffer - only good for immediate use by printf etc */
-extern "C" const char *gasname(struct gasmix gasmix)
+const char *gasname(struct gasmix gasmix)
 {
 	static char gas[64];
 	get_gas_string(gasmix, gas, sizeof(gas));
 	return gas;
 }
 
-extern "C" int gas_volume(const cylinder_t *cyl, pressure_t p)
+int gas_volume(const cylinder_t *cyl, pressure_t p)
 {
 	double bar = p.mbar / 1000.0;
 	double z_factor = gas_compressibility_factor(cyl->gasmix, bar);
 	return lrint(cyl->type.size.mliter * bar_to_atm(bar) / z_factor);
 }
 
-extern "C" int find_best_gasmix_match(struct gasmix mix, const struct cylinder_table *cylinders)
+int find_best_gasmix_match(struct gasmix mix, const struct cylinder_table *cylinders)
 {
 	int i;
 	int best = -1, score = INT_MAX;
@@ -355,18 +355,18 @@ struct std::vector<ws_info> ws_info_table = {
 	{ QT_TRANSLATE_NOOP("gettextFromC", "clip-on"), weight_t() },
 };
 
-extern "C" void remove_cylinder(struct dive *dive, int idx)
+void remove_cylinder(struct dive *dive, int idx)
 {
 	remove_from_cylinder_table(&dive->cylinders, idx);
 }
 
-extern "C" void remove_weightsystem(struct dive *dive, int idx)
+void remove_weightsystem(struct dive *dive, int idx)
 {
 	remove_from_weightsystem_table(&dive->weightsystems, idx);
 }
 
 // ws is cloned.
-extern "C" void set_weightsystem(struct dive *dive, int idx, weightsystem_t ws)
+void set_weightsystem(struct dive *dive, int idx, weightsystem_t ws)
 {
 	if (idx < 0 || idx >= dive->weightsystems.nr)
 		return;
@@ -376,7 +376,7 @@ extern "C" void set_weightsystem(struct dive *dive, int idx, weightsystem_t ws)
 
 /* when planning a dive we need to make sure that all cylinders have a sane depth assigned
  * and if we are tracking gas consumption the pressures need to be reset to start = end = workingpressure */
-extern "C" void reset_cylinders(struct dive *dive, bool track_gas)
+void reset_cylinders(struct dive *dive, bool track_gas)
 {
 	pressure_t decopo2 = {.mbar = prefs.decopo2};
 
@@ -403,7 +403,7 @@ static void copy_cylinder_type(const cylinder_t *s, cylinder_t *d)
 }
 
 /* copy the equipment data part of the cylinders but keep pressures */
-extern "C" void copy_cylinder_types(const struct dive *s, struct dive *d)
+void copy_cylinder_types(const struct dive *s, struct dive *d)
 {
 	int i;
 	if (!s || !d)
@@ -416,7 +416,7 @@ extern "C" void copy_cylinder_types(const struct dive *s, struct dive *d)
 		add_cloned_cylinder(&d->cylinders, *get_cylinder(s, i));
 }
 
-extern "C" cylinder_t *add_empty_cylinder(struct cylinder_table *t)
+cylinder_t *add_empty_cylinder(struct cylinder_table *t)
 {
 	cylinder_t cyl = empty_cylinder;
 	cyl.type.description = strdup("");
@@ -432,7 +432,7 @@ extern "C" cylinder_t *add_empty_cylinder(struct cylinder_table *t)
  *   Multiple cylinders might be created if the index is bigger than the
  *   number of existing cylinders
  */
-extern "C" cylinder_t *get_cylinder(const struct dive *d, int idx)
+cylinder_t *get_cylinder(const struct dive *d, int idx)
 {
 	/* FIXME: The planner uses a dummy cylinder one past the official number of cylinders
 	 * in the table to mark no-cylinder surface interavals. This is horrendous. Fix ASAP. */
@@ -444,7 +444,7 @@ extern "C" cylinder_t *get_cylinder(const struct dive *d, int idx)
 	return &d->cylinders.cylinders[idx];
 }
 
-extern "C" cylinder_t *get_or_create_cylinder(struct dive *d, int idx)
+cylinder_t *get_or_create_cylinder(struct dive *d, int idx)
 {
 	if (idx < 0) {
 		report_info("Warning: accessing invalid cylinder %d", idx);
@@ -456,7 +456,7 @@ extern "C" cylinder_t *get_or_create_cylinder(struct dive *d, int idx)
 }
 
 /* if a default cylinder is set, use that */
-extern "C" void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
+void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
 {
 	const char *cyl_name = prefs.default_cylinder;
 	pressure_t pO2 = {.mbar = static_cast<int>(lrint(prefs.modpO2 * 1000.0))};
@@ -481,7 +481,7 @@ extern "C" void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
 	}
 }
 
-extern "C" cylinder_t create_new_cylinder(const struct dive *d)
+cylinder_t create_new_cylinder(const struct dive *d)
 {
 	cylinder_t cyl = empty_cylinder;
 	fill_default_cylinder(d, &cyl);
@@ -537,7 +537,7 @@ static bool show_cylinder(const struct dive *d, int i)
 }
 
 /* The unused cylinders at the end of the cylinder list are hidden. */
-extern "C" int first_hidden_cylinder(const struct dive *d)
+int first_hidden_cylinder(const struct dive *d)
 {
 	int res = d->cylinders.nr;
 	while (res > 0 && !show_cylinder(d, res - 1))
@@ -546,7 +546,7 @@ extern "C" int first_hidden_cylinder(const struct dive *d)
 }
 
 #ifdef DEBUG_CYL
-extern "C" void dump_cylinders(struct dive *dive, bool verbose)
+void dump_cylinders(struct dive *dive, bool verbose)
 {
 	printf("Cylinder list:\n");
 	for (int i = 0; i < dive->cylinders; i++) {
diff --git a/core/equipment.h b/core/equipment.h
index a048b49bf..fd15b59c6 100644
--- a/core/equipment.h
+++ b/core/equipment.h
@@ -8,8 +8,6 @@
 #include <string>
 #include <vector>
 
-extern "C" {
-
 struct dive;
 
 enum cylinderuse {OC_GAS, DILUENT, OXYGEN, NOT_USED, NUM_GAS_USE}; // The different uses for cylinders
@@ -109,8 +107,6 @@ extern void add_cylinder(struct cylinder_table *, int idx, cylinder_t cyl);
 void get_gas_string(struct gasmix gasmix, char *text, int len);
 const char *gasname(struct gasmix gasmix);
 
-}
-
 struct ws_info {
 	std::string name;
 	weight_t weight;
diff --git a/core/errorhelper.h b/core/errorhelper.h
index f90927d8e..6c85ea64e 100644
--- a/core/errorhelper.h
+++ b/core/errorhelper.h
@@ -4,8 +4,6 @@
 
 // error reporting functions
 
-extern "C" {
-
 #ifdef __GNUC__
 #define __printf(x, y) __attribute__((__format__(__printf__, x, y)))
 #else
@@ -17,6 +15,4 @@ extern int __printf(1, 2) report_error(const char *fmt, ...);
 extern void __printf(1, 2) report_info(const char *fmt, ...);
 extern void set_error_cb(void(*cb)(char *));	// Callback takes ownership of passed string
 
-}
-
 #endif
diff --git a/core/event.h b/core/event.h
index 413da7248..66ee0bffc 100644
--- a/core/event.h
+++ b/core/event.h
@@ -8,8 +8,6 @@
 
 #include <libdivecomputer/parser.h>
 
-extern "C" {
-
 enum event_severity {
 	EVENT_SEVERITY_NONE = 0,
 	EVENT_SEVERITY_INFO,
@@ -58,6 +56,4 @@ extern enum event_severity get_event_severity(const struct event *ev);
 extern const struct event *get_next_event(const struct event *event, const char *name);
 extern struct event *get_next_event_mutable(struct event *event, const char *name);
 
-}
-
 #endif
diff --git a/core/eventtype.cpp b/core/eventtype.cpp
index 5e88480a1..8fbeb2703 100644
--- a/core/eventtype.cpp
+++ b/core/eventtype.cpp
@@ -27,12 +27,12 @@ static bool operator==(const event_type &en1, const event_type &en2)
 	return en1.name == en2.name && en1.severity == en2.severity;
 }
 
-extern "C" void clear_event_types()
+void clear_event_types()
 {
 	event_types.clear();
 }
 
-extern "C" void remember_event_type(const struct event *ev)
+void remember_event_type(const struct event *ev)
 {
 	if (empty_string(ev->name))
 		return;
@@ -42,33 +42,33 @@ extern "C" void remember_event_type(const struct event *ev)
 	event_types.push_back(std::move(type));
 }
 
-extern "C" bool is_event_type_hidden(const struct event *ev)
+bool is_event_type_hidden(const struct event *ev)
 {
 	auto it = std::find(event_types.begin(), event_types.end(), ev);
 	return it != event_types.end() && !it->plot;
 }
 
-extern "C" void hide_event_type(const struct event *ev)
+void hide_event_type(const struct event *ev)
 {
 	auto it = std::find(event_types.begin(), event_types.end(), ev);
 	if (it != event_types.end())
 		it->plot = false;
 }
 
-extern "C" void show_all_event_types()
+void show_all_event_types()
 {
 	for (event_type &e: event_types)
 		e.plot = true;
 }
 
-extern "C" void show_event_type(int idx)
+void show_event_type(int idx)
 {
 	if (idx < 0 || idx >= (int)event_types.size())
 		return;
 	event_types[idx].plot = true;
 }
 
-extern "C" bool any_event_types_hidden()
+bool any_event_types_hidden()
 {
 	return std::any_of(event_types.begin(), event_types.end(),
 			   [] (const event_type &e) { return !e.plot; });
diff --git a/core/eventtype.h b/core/eventtype.h
index 37a589424..8f0ecd28e 100644
--- a/core/eventtype.h
+++ b/core/eventtype.h
@@ -6,8 +6,6 @@
 #include <vector>
 #include <QString>
 
-extern "C" {
-
 extern void clear_event_types(void);
 extern void remember_event_type(const struct event *ev);
 extern bool is_event_type_hidden(const struct event *ev);
@@ -15,11 +13,8 @@ extern void hide_event_type(const struct event *ev);
 extern void show_all_event_types();
 extern void show_event_type(int idx);
 extern bool any_event_types_hidden();
-
-}
-
 extern std::vector<int> hidden_event_types();
-QString event_type_name(const event *ev);
-QString event_type_name(int idx);
+extern QString event_type_name(const event *ev);
+extern QString event_type_name(int idx);
 
 #endif
diff --git a/core/file.cpp b/core/file.cpp
index dd9f15b8b..93ba907d5 100644
--- a/core/file.cpp
+++ b/core/file.cpp
@@ -78,7 +78,7 @@ static void zip_read(struct zip_file *file, const char *filename, struct divelog
 	(void) parse_xml_buffer(filename, mem.data(), read, log, NULL);
 }
 
-extern "C" int try_to_open_zip(const char *filename, struct divelog *log)
+int try_to_open_zip(const char *filename, struct divelog *log)
 {
 	int success = 0;
 	/* Grr. libzip needs to re-open the file, it can't take a buffer */
@@ -268,7 +268,7 @@ bool remote_repo_uptodate(const char *filename, struct git_info *info)
 	return false;
 }
 
-extern "C" int parse_file(const char *filename, struct divelog *log)
+int parse_file(const char *filename, struct divelog *log)
 {
 	struct git_info info;
 	const char *fmt;
diff --git a/core/file.h b/core/file.h
index 3f93a2f72..054fd384b 100644
--- a/core/file.h
+++ b/core/file.h
@@ -12,7 +12,6 @@
 struct divelog;
 struct zip;
 
-extern "C" {
 extern void ostctools_import(const char *file, struct divelog *log);
 
 extern int parse_file(const char *filename, struct divelog *log);
@@ -28,11 +27,7 @@ extern int subsurface_access(const char *path, int mode);
 extern int subsurface_stat(const char *path, struct stat *buf);
 extern struct zip *subsurface_zip_open_readonly(const char *path, int flags, int *errorp);
 extern int subsurface_zip_close(struct zip *zip);
-
-}
-
-// return data, errorcode pair.
-extern std::pair<std::string, int> readfile(const char *filename);
+extern std::pair<std::string, int> readfile(const char *filename); // return data, errorcode pair.
 extern int try_to_open_cochran(const char *filename, std::string &mem, struct divelog *log);
 extern int try_to_open_liquivision(const char *filename, std::string &mem, struct divelog *log);
 extern int datatrak_import(std::string &mem, std::string &wl_mem, struct divelog *log);
diff --git a/core/filterconstraint.cpp b/core/filterconstraint.cpp
index 55444495e..16f2fe633 100644
--- a/core/filterconstraint.cpp
+++ b/core/filterconstraint.cpp
@@ -164,57 +164,57 @@ static enum filter_constraint_range_mode filter_constraint_range_mode_from_strin
 	return FILTER_CONSTRAINT_EQUAL;
 }
 
-extern "C" const char *filter_constraint_type_to_string(enum filter_constraint_type type)
+const char *filter_constraint_type_to_string(enum filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc ? desc->token : "unknown";
 }
 
-extern "C" const char *filter_constraint_string_mode_to_string(enum filter_constraint_string_mode mode)
+const char *filter_constraint_string_mode_to_string(enum filter_constraint_string_mode mode)
 {
 	const string_mode_description *desc = get_string_mode_description(mode);
 	return desc ? desc->token : "unknown";
 }
 
-extern "C" const char *filter_constraint_range_mode_to_string(enum filter_constraint_range_mode mode)
+const char *filter_constraint_range_mode_to_string(enum filter_constraint_range_mode mode)
 {
 	const range_mode_description *desc = get_range_mode_description(mode);
 	return desc ? desc->token : "unknown";
 }
 
-extern "C" int filter_constraint_type_to_index(enum filter_constraint_type type)
+int filter_constraint_type_to_index(enum filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc ? desc - type_descriptions : -1;
 }
 
-extern "C" int filter_constraint_string_mode_to_index(enum filter_constraint_string_mode mode)
+int filter_constraint_string_mode_to_index(enum filter_constraint_string_mode mode)
 {
 	const string_mode_description *desc = get_string_mode_description(mode);
 	return desc ? desc - string_mode_descriptions : -1;
 }
 
-extern "C" int filter_constraint_range_mode_to_index(enum filter_constraint_range_mode mode)
+int filter_constraint_range_mode_to_index(enum filter_constraint_range_mode mode)
 {
 	const range_mode_description *desc = get_range_mode_description(mode);
 	return desc ? desc - range_mode_descriptions : -1;
 }
 
-extern "C" enum filter_constraint_type filter_constraint_type_from_index(int index)
+enum filter_constraint_type filter_constraint_type_from_index(int index)
 {
 	if (index >= 0 && index < (int)std::size(type_descriptions))
 		return type_descriptions[index].type;
 	return (enum filter_constraint_type)-1;
 }
 
-extern "C" enum filter_constraint_string_mode filter_constraint_string_mode_from_index(int index)
+enum filter_constraint_string_mode filter_constraint_string_mode_from_index(int index)
 {
 	if (index >= 0 && index < (int)std::size(string_mode_descriptions))
 		return string_mode_descriptions[index].mode;
 	return (enum filter_constraint_string_mode)-1;
 }
 
-extern "C" enum filter_constraint_range_mode filter_constraint_range_mode_from_index(int index)
+enum filter_constraint_range_mode filter_constraint_range_mode_from_index(int index)
 {
 	if (index >= 0 && index < (int)std::size(range_mode_descriptions))
 		return range_mode_descriptions[index].mode;
@@ -390,7 +390,7 @@ QStringList filter_contraint_multiple_choice_translated(enum filter_constraint_t
 	return QStringList();
 }
 
-extern "C" bool filter_constraint_is_string(filter_constraint_type type)
+bool filter_constraint_is_string(filter_constraint_type type)
 {
 	// Currently a constraint is filter based if and only if it has a string
 	// mode (i.e. starts with, substring, exact). In the future we might also
@@ -398,7 +398,7 @@ extern "C" bool filter_constraint_is_string(filter_constraint_type type)
 	return filter_constraint_has_string_mode(type);
 }
 
-extern "C" bool filter_constraint_is_timestamp(filter_constraint_type type)
+bool filter_constraint_is_timestamp(filter_constraint_type type)
 {
 	return type == FILTER_CONSTRAINT_DATE || type == FILTER_CONSTRAINT_DATE_TIME;
 }
@@ -408,37 +408,37 @@ static bool is_numerical_constraint(filter_constraint_type type)
 	return !filter_constraint_is_string(type) && !filter_constraint_is_timestamp(type);
 }
 
-extern "C" bool filter_constraint_has_string_mode(enum filter_constraint_type type)
+bool filter_constraint_has_string_mode(enum filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc && desc->has_string_mode;
 }
 
-extern "C" bool filter_constraint_has_range_mode(enum filter_constraint_type type)
+bool filter_constraint_has_range_mode(enum filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc && desc->has_range_mode;
 }
 
-extern "C" bool filter_constraint_is_star(filter_constraint_type type)
+bool filter_constraint_is_star(filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc && desc->is_star_widget;
 }
 
-extern "C" bool filter_constraint_has_date_widget(filter_constraint_type type)
+bool filter_constraint_has_date_widget(filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc && desc->has_date;
 }
 
-extern "C" bool filter_constraint_has_time_widget(filter_constraint_type type)
+bool filter_constraint_has_time_widget(filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc && desc->has_time;
 }
 
-extern "C" int filter_constraint_num_decimals(enum filter_constraint_type type)
+int filter_constraint_num_decimals(enum filter_constraint_type type)
 {
 	const type_description *desc = get_type_description(type);
 	return desc ? desc->decimal_places : 1;
@@ -446,7 +446,7 @@ extern "C" int filter_constraint_num_decimals(enum filter_constraint_type type)
 
 // String constraints are valid if there is at least one term.
 // Other constraints are always valid.
-extern "C" bool filter_constraint_is_valid(const struct filter_constraint *constraint)
+bool filter_constraint_is_valid(const struct filter_constraint *constraint)
 {
 	if (!filter_constraint_is_string(constraint->type))
 		return true;
diff --git a/core/filterconstraint.h b/core/filterconstraint.h
index 684c30448..e9c85ec0b 100644
--- a/core/filterconstraint.h
+++ b/core/filterconstraint.h
@@ -9,8 +9,6 @@
 
 struct dive;
 
-extern "C" {
-
 enum filter_constraint_type {
 	FILTER_CONSTRAINT_DATE,
 	FILTER_CONSTRAINT_DATE_TIME,
@@ -111,8 +109,6 @@ extern bool filter_constraint_has_time_widget(enum filter_constraint_type);
 extern int filter_constraint_num_decimals(enum filter_constraint_type);
 extern bool filter_constraint_is_valid(const struct filter_constraint *constraint);
 
-}
-
 QString filter_constraint_type_to_string_translated(enum filter_constraint_type);
 QString filter_constraint_negate_to_string_translated(bool negate);
 QString filter_constraint_string_mode_to_string_translated(enum filter_constraint_string_mode);
diff --git a/core/filterpreset.cpp b/core/filterpreset.cpp
index fa07f5879..518b2b264 100644
--- a/core/filterpreset.cpp
+++ b/core/filterpreset.cpp
@@ -9,7 +9,7 @@ static filter_preset_table &global_table()
 	return *divelog.filter_presets;
 }
 
-extern "C" int filter_presets_count(void)
+int filter_presets_count(void)
 {
 	return (int)global_table().size();
 }
@@ -19,7 +19,7 @@ extern std::string filter_preset_fulltext_query(int preset)
 	return global_table()[preset].data.fullText.originalQuery.toStdString();
 }
 
-extern "C" const char *filter_preset_fulltext_mode(int preset)
+const char *filter_preset_fulltext_mode(int preset)
 {
 	switch (global_table()[preset].data.fulltextStringMode) {
 	default:
@@ -32,7 +32,7 @@ extern "C" const char *filter_preset_fulltext_mode(int preset)
 	}
 }
 
-extern "C" void filter_preset_set_fulltext(struct filter_preset *preset, const char *fulltext, const char *fulltext_string_mode)
+void filter_preset_set_fulltext(struct filter_preset *preset, const char *fulltext, const char *fulltext_string_mode)
 {
 	if (same_string(fulltext_string_mode, "substring"))
 		preset->data.fulltextStringMode = StringFilterMode::SUBSTRING;
@@ -43,17 +43,17 @@ extern "C" void filter_preset_set_fulltext(struct filter_preset *preset, const c
 	preset->data.fullText = fulltext;
 }
 
-extern "C" int filter_preset_constraint_count(int preset)
+int filter_preset_constraint_count(int preset)
 {
 	return (int)global_table()[preset].data.constraints.size();
 }
 
-extern "C" const filter_constraint *filter_preset_constraint(int preset, int constraint)
+const filter_constraint *filter_preset_constraint(int preset, int constraint)
 {
 	return &global_table()[preset].data.constraints[constraint];
 }
 
-extern "C" void filter_preset_set_name(struct filter_preset *preset, const char *name)
+void filter_preset_set_name(struct filter_preset *preset, const char *name)
 {
 	preset->name = name;
 }
@@ -83,13 +83,13 @@ static std::string get_unique_preset_name(const std::string &orig, const struct
 	return res;
 }
 
-extern "C" void add_filter_preset_to_table(const struct filter_preset *preset, struct filter_preset_table *table)
+void add_filter_preset_to_table(const struct filter_preset *preset, struct filter_preset_table *table)
 {
 	std::string name = get_unique_preset_name(preset->name, *table);
 	filter_preset_add_to_table(name, preset->data, *table);
 }
 
-extern "C" void filter_preset_add_constraint(struct filter_preset *preset, const char *type, const char *string_mode,
+void filter_preset_add_constraint(struct filter_preset *preset, const char *type, const char *string_mode,
 					     const char *range_mode, bool negate, const char *data)
 {
 	preset->data.constraints.emplace_back(type, string_mode, range_mode, negate, data);
diff --git a/core/filterpreset.h b/core/filterpreset.h
index 40037a948..807a1c48c 100644
--- a/core/filterpreset.h
+++ b/core/filterpreset.h
@@ -29,8 +29,6 @@ struct filter_preset_table : public std::vector<filter_preset>
 {
 };
 
-extern "C" {
-
 // The C IO code accesses the filter presets via integer indices.
 extern int filter_presets_count(void);
 extern const char *filter_preset_fulltext_mode(int preset); // string mode of fulltext query. ownership is *not* passed to caller.
@@ -41,9 +39,6 @@ extern void filter_preset_set_fulltext(struct filter_preset *preset, const char
 extern void add_filter_preset_to_table(const struct filter_preset *preset, struct filter_preset_table *table);
 extern void filter_preset_add_constraint(struct filter_preset *preset, const char *type, const char *string_mode,
 					 const char *range_mode, bool negate, const char *data); // called by the parser, therefore data passed as strings.
-
-}
-
 int filter_preset_id(const std::string &s); // for now, we assume that names are unique. returns -1 if no preset with that name.
 void filter_preset_set(int preset, const FilterData &d); // this will override a preset if the name already exists.
 FilterData filter_preset_get(int preset);
diff --git a/core/fulltext.cpp b/core/fulltext.cpp
index 64899b647..563d6967c 100644
--- a/core/fulltext.cpp
+++ b/core/fulltext.cpp
@@ -35,8 +35,6 @@ static FullText self;
 
 // C-interface functions
 
-extern "C" {
-
 void fulltext_register(struct dive *d)
 {
 	self.registerDive(d);
@@ -57,8 +55,6 @@ void fulltext_populate()
 	self.populate();
 }
 
-} // extern "C"
-
 // C++-only interface functions
 FullTextResult fulltext_find_dives(const FullTextQuery &q, StringFilterMode mode)
 {
diff --git a/core/fulltext.h b/core/fulltext.h
index 688db63d1..52fb77f69 100644
--- a/core/fulltext.h
+++ b/core/fulltext.h
@@ -14,9 +14,8 @@
 #ifndef FULLTEXT_H
 #define FULLTEXT_H
 
-// 1) The C-accessible interface
-
-extern "C" {
+#include <QString>
+#include <vector>
 
 struct full_text_cache;
 struct dive;
@@ -25,13 +24,6 @@ void fulltext_unregister(struct dive *d); // Note: can be called repeatedly
 void fulltext_unregister_all(); // Unregisters all dives in the dive table
 void fulltext_populate(); // Registers all dives in the dive table
 
-}
-
-// 2) The C++-only interface
-
-#include <QString>
-#include <vector>
-
 enum class StringFilterMode {
 	SUBSTRING = 0,
 	STARTSWITH = 1,
diff --git a/core/gas.h b/core/gas.h
index 03a73f613..59cbd5307 100644
--- a/core/gas.h
+++ b/core/gas.h
@@ -5,8 +5,6 @@
 #include "divemode.h"
 #include "units.h"
 
-extern "C" {
-
 enum gas_component { N2, HE, O2 };
 
 // o2 == 0 && he == 0 -> air
@@ -71,6 +69,4 @@ extern enum gastype gasmix_to_type(struct gasmix mix);
 extern const char *gastype_name(enum gastype type);
 extern fraction_t make_fraction(int f);
 
-}
-
 #endif
diff --git a/core/gettext.h b/core/gettext.h
index c7fe5a2ae..b0a70c067 100644
--- a/core/gettext.h
+++ b/core/gettext.h
@@ -2,7 +2,7 @@
 #ifndef MYGETTEXT_H
 #define MYGETTEXT_H
 
-extern "C" const char *trGettext(const char *);
+const char *trGettext(const char *);
 static inline const char *translate(const char *, const char *arg)
 {
 	return trGettext(arg);
diff --git a/core/gettextfromc.cpp b/core/gettextfromc.cpp
index c3a592f5b..0dab3db83 100644
--- a/core/gettextfromc.cpp
+++ b/core/gettextfromc.cpp
@@ -6,7 +6,7 @@
 static QHash<QByteArray, QByteArray> translationCache;
 static QMutex lock;
 
-extern "C" const char *trGettext(const char *text)
+const char *trGettext(const char *text)
 {
 	QByteArray key(text);
 	QMutexLocker l(&lock);
diff --git a/core/gettextfromc.h b/core/gettextfromc.h
index 647ea52a8..23b407f9a 100644
--- a/core/gettextfromc.h
+++ b/core/gettextfromc.h
@@ -4,7 +4,7 @@
 
 #include <QCoreApplication>
 
-extern "C" const char *trGettext(const char *text);
+const char *trGettext(const char *text);
 
 class gettextFromC {
 	Q_DECLARE_TR_FUNCTIONS(gettextFromC)
diff --git a/core/git-access.cpp b/core/git-access.cpp
index ca22659bb..0543a1089 100644
--- a/core/git-access.cpp
+++ b/core/git-access.cpp
@@ -58,7 +58,7 @@ static bool includes_string_caseinsensitive(const char *haystack, const char *ne
 	return 0;
 }
 
-extern "C" void set_git_update_cb(int(*cb)(const char *))
+void set_git_update_cb(int(*cb)(const char *))
 {
 	update_progress_cb = cb;
 }
@@ -69,7 +69,7 @@ extern "C" void set_git_update_cb(int(*cb)(const char *))
 // proportional - some parts are based on compute performance, some on network speed)
 // they also provide information where in the process we are so we can analyze the log
 // to understand which parts of the process take how much time.
-extern "C" int git_storage_update_progress(const char *text)
+int git_storage_update_progress(const char *text)
 {
 	int ret = 0;
 	if (update_progress_cb)
@@ -241,7 +241,7 @@ static bool exceeded_auth_attempts()
 	return false;
 }
 
-extern "C" int credential_ssh_cb(git_cred **out,
+int credential_ssh_cb(git_cred **out,
 		  const char *,
 		  const char *,
 		  unsigned int allowed_types,
@@ -273,7 +273,7 @@ extern "C" int credential_ssh_cb(git_cred **out,
 	return GIT_EUSER;
 }
 
-extern "C" int credential_https_cb(git_cred **out,
+int credential_https_cb(git_cred **out,
 			const char *,
 			const char *,
 			unsigned int,
@@ -288,7 +288,7 @@ extern "C" int credential_https_cb(git_cred **out,
 	return git_cred_userpass_plaintext_new(out, username, password);
 }
 
-extern "C" int certificate_check_cb(git_cert *cert, int valid, const char *host, void *)
+int certificate_check_cb(git_cert *cert, int valid, const char *host, void *)
 {
 	if (verbose)
 		report_info("git storage: certificate callback for host %s with validity %d\n", host, valid);
@@ -339,7 +339,7 @@ static int update_remote(struct git_info *info, git_remote *origin, git_referenc
 	return 0;
 }
 
-extern "C" int update_git_checkout(git_repository *repo, git_object *parent, git_tree *tree);
+int update_git_checkout(git_repository *repo, git_object *parent, git_tree *tree);
 
 static int try_to_git_merge(struct git_info *info, git_reference **local_p, git_reference *, git_oid *base, const git_oid *local_id, const git_oid *remote_id)
 {
diff --git a/core/git-access.h b/core/git-access.h
index c3e706509..ed9e4ed5e 100644
--- a/core/git-access.h
+++ b/core/git-access.h
@@ -11,8 +11,6 @@ struct git_oid;
 struct git_repository;
 struct divelog;
 
-extern "C" {
-
 #define CLOUD_HOST_US "ssrf-cloud-us.subsurface-divelog.org"  // preferred (faster/bigger) server in the US
 #define CLOUD_HOST_U2 "ssrf-cloud-u2.subsurface-divelog.org"  // secondary (older) server in the US
 #define CLOUD_HOST_EU "ssrf-cloud-eu.subsurface-divelog.org"  // preferred (faster/bigger) server in Germany
@@ -30,8 +28,6 @@ void set_git_update_cb(int(*)(const char *));
 int git_storage_update_progress(const char *text);
 int get_authorship(git_repository *repo, git_signature **authorp);
 
-}
-
 struct git_info {
 	std::string url;
 	std::string branch;
diff --git a/core/import-cobalt.cpp b/core/import-cobalt.cpp
index 093232328..2b199ba9c 100644
--- a/core/import-cobalt.cpp
+++ b/core/import-cobalt.cpp
@@ -199,7 +199,7 @@ static int cobalt_dive(void *param, int, char **data, char **)
 	return SQLITE_OK;
 }
 
-extern "C" int parse_cobalt_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_cobalt_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	struct parser_state state;
diff --git a/core/import-csv.cpp b/core/import-csv.cpp
index 777db16a9..6d3e7ef7a 100644
--- a/core/import-csv.cpp
+++ b/core/import-csv.cpp
@@ -270,7 +270,7 @@ static int parse_dan_format(const char *filename, struct xml_params *params, str
 	return ret;
 }
 
-extern "C" int parse_csv_file(const char *filename, struct xml_params *params, const char *csvtemplate, struct divelog *log)
+int parse_csv_file(const char *filename, struct xml_params *params, const char *csvtemplate, struct divelog *log)
 {
 	int ret;
 	std::string mem;
diff --git a/core/import-csv.h b/core/import-csv.h
index e3ff5f950..7247a516a 100644
--- a/core/import-csv.h
+++ b/core/import-csv.h
@@ -21,8 +21,6 @@ enum csv_format {
 
 #define MAXCOLDIGITS 10
 
-extern "C" {
-
 int parse_csv_file(const char *filename, struct xml_params *params, const char *csvtemplate, struct divelog *log);
 int try_to_open_csv(std::string &mem, enum csv_format type, struct divelog *log);
 int parse_txt_file(const char *filename, const char *csv, struct divelog *log);
@@ -30,6 +28,4 @@ int parse_txt_file(const char *filename, const char *csv, struct divelog *log);
 int parse_seabear_log(const char *filename, struct divelog *log);
 int parse_manual_file(const char *filename, struct xml_params *params, struct divelog *log);
 
-}
-
 #endif // IMPORTCSV_H
diff --git a/core/import-divinglog.cpp b/core/import-divinglog.cpp
index 04b0a9a3a..50eba6927 100644
--- a/core/import-divinglog.cpp
+++ b/core/import-divinglog.cpp
@@ -384,7 +384,7 @@ static int divinglog_dive(void *param, int, char **data, char **)
 }
 
 
-extern "C" int parse_divinglog_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_divinglog_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	struct parser_state state;
diff --git a/core/import-seac.cpp b/core/import-seac.cpp
index 07416e47e..5ee9ac18e 100644
--- a/core/import-seac.cpp
+++ b/core/import-seac.cpp
@@ -264,7 +264,7 @@ static int seac_dive(void *param, int, char **data, char **)
  * The callback function performs another SQL query on the other
  * table, to read in the sample values.
  */
-extern "C" int parse_seac_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_seac_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	char *err = NULL;
diff --git a/core/import-shearwater.cpp b/core/import-shearwater.cpp
index f9924e67d..8f559ca6c 100644
--- a/core/import-shearwater.cpp
+++ b/core/import-shearwater.cpp
@@ -473,7 +473,7 @@ static int shearwater_cloud_dive(void *param, int, char **data, char **)
 	return SQLITE_OK;
 }
 
-extern "C" int parse_shearwater_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_shearwater_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	struct parser_state state;
@@ -496,7 +496,7 @@ extern "C" int parse_shearwater_buffer(sqlite3 *handle, const char *url, const c
 	return 0;
 }
 
-extern "C" int parse_shearwater_cloud_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_shearwater_cloud_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	struct parser_state state;
diff --git a/core/import-suunto.cpp b/core/import-suunto.cpp
index 3b65c954f..5859b0bdf 100644
--- a/core/import-suunto.cpp
+++ b/core/import-suunto.cpp
@@ -277,7 +277,7 @@ static int dm4_dive(void *param, int, char **data, char **)
 	return SQLITE_OK;
 }
 
-extern "C" int parse_dm4_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_dm4_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	char *err = NULL;
@@ -549,7 +549,7 @@ static int dm5_dive(void *param, int, char **data, char **)
 	return SQLITE_OK;
 }
 
-extern "C" int parse_dm5_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
+int parse_dm5_buffer(sqlite3 *handle, const char *url, const char *, int, struct divelog *log)
 {
 	int retval;
 	char *err = NULL;
diff --git a/core/ios.cpp b/core/ios.cpp
index 409ff63ca..15f1c4501 100644
--- a/core/ios.cpp
+++ b/core/ios.cpp
@@ -32,8 +32,6 @@ static std::string make_default_filename()
 	return system_default_path() + "/subsurface.xml";
 }
 
-extern "C" {
-
 const char mac_system_divelist_default_font[] = "Arial";
 const char *system_divelist_default_font = mac_system_divelist_default_font;
 double system_divelist_default_font_size = -1.0;
@@ -123,4 +121,3 @@ bool subsurface_user_is_root()
 {
 	return false;
 }
-}
diff --git a/core/libdivecomputer.h b/core/libdivecomputer.h
index 84aebdbab..afb8ebc91 100644
--- a/core/libdivecomputer.h
+++ b/core/libdivecomputer.h
@@ -21,8 +21,6 @@
 #define dc_usb_storage_open(stream, context, devname) (DC_STATUS_UNSUPPORTED)
 #endif
 
-extern "C" {
-
 struct dive;
 struct divelog;
 struct devices;
@@ -73,6 +71,4 @@ unsigned int get_supported_transports(device_data_t *data);
 extern std::string logfile_name;
 extern std::string dumpfile_name;
 
-}
-
 #endif // LIBDIVECOMPUTER_H
diff --git a/core/load-git.cpp b/core/load-git.cpp
index 1d8ec98f9..5a1ed3b7f 100644
--- a/core/load-git.cpp
+++ b/core/load-git.cpp
@@ -1850,12 +1850,12 @@ static int load_dives_from_tree(git_repository *repo, git_tree *tree, struct git
 	return 0;
 }
 
-extern "C" void clear_git_id(void)
+void clear_git_id(void)
 {
 	saved_git_id.clear();
 }
 
-extern "C" void set_git_id(const struct git_oid *id)
+void set_git_id(const struct git_oid *id)
 {
 	char git_id_buffer[GIT_OID_HEXSZ + 1];
 
diff --git a/core/macos.cpp b/core/macos.cpp
index 1bec49fda..4c7c1426e 100644
--- a/core/macos.cpp
+++ b/core/macos.cpp
@@ -48,8 +48,6 @@ static std::string make_default_filename()
 	return system_default_path() + "/" + user + ".xml";
 }
 
-extern "C" {
-
 const char mac_system_divelist_default_font[] = "Arial";
 const char *system_divelist_default_font = mac_system_divelist_default_font;
 double system_divelist_default_font_size = -1.0;
@@ -199,5 +197,3 @@ bool subsurface_user_is_root()
 {
 	return geteuid() == 0;
 }
-
-}
diff --git a/core/membuffer.h b/core/membuffer.h
index 450ac4811..3c744bb08 100644
--- a/core/membuffer.h
+++ b/core/membuffer.h
@@ -52,8 +52,6 @@ struct membufferpp : public membuffer {
 	~membufferpp();
 };
 
-extern "C" {
-
 #ifdef __GNUC__
 #define __printf(x, y) __attribute__((__format__(__printf__, x, y)))
 #else
@@ -113,6 +111,4 @@ extern void put_salinity(struct membuffer *, int, const char *, const char *);
 extern void put_degrees(struct membuffer *b, degrees_t value, const char *, const char *);
 extern void put_location(struct membuffer *b, const location_t *, const char *, const char *);
 
-}
-
 #endif
diff --git a/core/metadata.cpp b/core/metadata.cpp
index dacfc9b1d..9bc9d35a6 100644
--- a/core/metadata.cpp
+++ b/core/metadata.cpp
@@ -528,7 +528,7 @@ static bool parseASF(QFile &f, metadata *metadata)
 	return false;
 }
 
-extern "C" mediatype_t get_metadata(const char *filename_in, metadata *data)
+mediatype_t get_metadata(const char *filename_in, metadata *data)
 {
 	data->timestamp = 0;
 	data->duration.seconds = 0;
@@ -561,7 +561,7 @@ extern "C" mediatype_t get_metadata(const char *filename_in, metadata *data)
 	return res;
 }
 
-extern "C" timestamp_t picture_get_timestamp(const char *filename)
+timestamp_t picture_get_timestamp(const char *filename)
 {
 	struct metadata data;
 	get_metadata(filename, &data);
diff --git a/core/metadata.h b/core/metadata.h
index 537eccc79..a3d854c5f 100644
--- a/core/metadata.h
+++ b/core/metadata.h
@@ -17,11 +17,7 @@ enum mediatype_t {
 	MEDIATYPE_STILL_LOADING,	// Still processing in the background
 };
 
-extern "C" {
-
 enum mediatype_t get_metadata(const char *filename, struct metadata *data);
 timestamp_t picture_get_timestamp(const char *filename);
 
-}
-
 #endif // METADATA_H
diff --git a/core/ostctools.cpp b/core/ostctools.cpp
index 73201e071..5d4b7631d 100644
--- a/core/ostctools.cpp
+++ b/core/ostctools.cpp
@@ -42,7 +42,7 @@ static int ostc_prepare_data(int data_model, dc_family_t dc_fam, device_data_t &
  * each file. So it's not necessary to iterate once and again on a parsing
  * function. Actually there's only one kind of archive for every DC model.
  */
-extern "C" void ostctools_import(const char *file, struct divelog *log)
+void ostctools_import(const char *file, struct divelog *log)
 {
 	FILE *archive;
 	device_data_t devdata;
diff --git a/core/owning_ptrs.h b/core/owning_ptrs.h
index 3ba5dc0a5..0eb2a0367 100644
--- a/core/owning_ptrs.h
+++ b/core/owning_ptrs.h
@@ -14,8 +14,8 @@ struct dive_trip;
 struct dive_site;
 struct event;
 
-extern "C" void free_dive(struct dive *);
-extern "C" void free_trip(struct dive_trip *);
+void free_dive(struct dive *);
+void free_trip(struct dive_trip *);
 
 // Classes used to automatically call the appropriate free_*() function for owning pointers that go out of scope.
 struct DiveDeleter {
diff --git a/core/parse-xml.cpp b/core/parse-xml.cpp
index 15a15b336..b623e9ddd 100644
--- a/core/parse-xml.cpp
+++ b/core/parse-xml.cpp
@@ -1186,7 +1186,7 @@ static void gps_long(const char *buffer, struct dive *dive, struct parser_state
 }
 
 /* We allow either spaces or a comma between the decimal degrees */
-extern "C" void parse_location(const char *buffer, location_t *loc)
+void parse_location(const char *buffer, location_t *loc)
 {
 	const char *end;
 	loc->lat = parse_degrees(buffer, &end);
@@ -1752,7 +1752,7 @@ static const char *preprocess_divelog_de(const char *buffer)
 	return buffer;
 }
 
-extern "C" int parse_xml_buffer(const char *url, const char *buffer, int, struct divelog *log,
+int parse_xml_buffer(const char *url, const char *buffer, int, struct divelog *log,
 				const struct xml_params *params)
 {
 	xmlDoc *doc;
@@ -1802,7 +1802,7 @@ static timestamp_t parse_dlf_timestamp(unsigned char *buffer)
 	return offset + 946684800;
 }
 
-extern "C" int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
+int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 {
 	using namespace std::string_literals;
 	unsigned char *ptr = buffer;
@@ -2274,12 +2274,12 @@ extern "C" int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divel
 }
 
 
-extern "C" void parse_xml_init(void)
+void parse_xml_init(void)
 {
 	LIBXML_TEST_VERSION
 }
 
-extern "C" void parse_xml_exit(void)
+void parse_xml_exit(void)
 {
 	xmlCleanupParser();
 }
diff --git a/core/parse.cpp b/core/parse.cpp
index fd283f647..c42519b9f 100644
--- a/core/parse.cpp
+++ b/core/parse.cpp
@@ -42,19 +42,19 @@ struct divecomputer *get_dc(struct parser_state *state)
 /*
  * Add a dive into the dive_table array
  */
-extern "C" void record_dive_to_table(struct dive *dive, struct dive_table *table)
+void record_dive_to_table(struct dive *dive, struct dive_table *table)
 {
 	add_to_dive_table(table, table->nr, fixup_dive(dive));
 }
 
-extern "C" void start_match(const char *type, const char *name, char *buffer)
+void start_match(const char *type, const char *name, char *buffer)
 {
 	if (verbose > 2)
 		printf("Matching %s '%s' (%s)\n",
 		       type, name, buffer);
 }
 
-extern "C" void nonmatch(const char *type, const char *name, char *buffer)
+void nonmatch(const char *type, const char *name, char *buffer)
 {
 	if (verbose > 1)
 		printf("Unable to match %s '%s' (%s)\n",
@@ -431,7 +431,7 @@ void userid_stop(struct parser_state *state)
  * therefore make sure to only pass in to NULL-initialized pointers or pointers
  * to owned strings
  */
-extern "C" void utf8_string(const char *buffer, char **res)
+void utf8_string(const char *buffer, char **res)
 {
 	free(*res);
 	while (isspace(*buffer))
@@ -510,7 +510,7 @@ void add_dive_site(const char *ds_name, struct dive *dive, struct parser_state *
 	}
 }
 
-extern "C" int atoi_n(char *ptr, unsigned int len)
+int atoi_n(char *ptr, unsigned int len)
 {
 	if (len < 10) {
 		char buf[10];
diff --git a/core/parse.h b/core/parse.h
index aaef654d3..f9152c8b0 100644
--- a/core/parse.h
+++ b/core/parse.h
@@ -142,8 +142,6 @@ void utf8_string_std(const char *buffer, std::string *res);
 
 void add_dive_site(const char *ds_name, struct dive *dive, struct parser_state *state);
 
-extern "C" {
-
 int trimspace(char *buffer);
 void start_match(const char *type, const char *name, char *buffer);
 void nonmatch(const char *type, const char *name, char *buffer);
@@ -161,7 +159,6 @@ int parse_shearwater_cloud_buffer(sqlite3 *handle, const char *url, const char *
 int parse_cobalt_buffer(sqlite3 *handle, const char *url, const char *buf, int size, struct divelog *log);
 int parse_divinglog_buffer(sqlite3 *handle, const char *url, const char *buf, int size, struct divelog *log);
 int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log);
-}
 std::string trimspace(const char *buffer);
 
 #endif
diff --git a/core/picture.h b/core/picture.h
index 1f5b80e5e..9999b9291 100644
--- a/core/picture.h
+++ b/core/picture.h
@@ -6,8 +6,6 @@
 #include "units.h"
 #include <stddef.h> // For NULL
 
-extern "C" {
-
 struct dive;
 
 struct picture {
@@ -46,6 +44,4 @@ extern void sort_picture_table(struct picture_table *);
 extern struct picture *create_picture(const char *filename, timestamp_t shift_time, bool match_all, struct dive **dive);
 extern bool picture_check_valid_time(timestamp_t timestamp, timestamp_t shift_time);
 
-}
-
 #endif // PICTURE_H
diff --git a/core/planner.cpp b/core/planner.cpp
index 3cd0a5d6b..09856269c 100644
--- a/core/planner.cpp
+++ b/core/planner.cpp
@@ -42,7 +42,7 @@ static int decostoplevels_imperial[] = { 0, 3048, 6096, 9144, 12192, 15240, 1828
 					325120, 345440, 365760, 386080 };
 
 #if DEBUG_PLAN
-extern "C" void dump_plan(struct diveplan *diveplan)
+void dump_plan(struct diveplan *diveplan)
 {
 	struct divedatapoint *dp;
 	struct tm tm;
@@ -65,7 +65,7 @@ extern "C" void dump_plan(struct diveplan *diveplan)
 }
 #endif
 
-extern "C" bool diveplan_empty(struct diveplan *diveplan)
+bool diveplan_empty(struct diveplan *diveplan)
 {
 	struct divedatapoint *dp;
 	if (!diveplan || !diveplan->dp)
@@ -80,7 +80,7 @@ extern "C" bool diveplan_empty(struct diveplan *diveplan)
 }
 
 /* get the cylinder index at a certain time during the dive */
-extern "C" int get_cylinderid_at_time(struct dive *dive, struct divecomputer *dc, duration_t time)
+int get_cylinderid_at_time(struct dive *dive, struct divecomputer *dc, duration_t time)
 {
 	// we start with the first cylinder unless an event tells us otherwise
 	int cylinder_idx = 0;
@@ -323,7 +323,7 @@ static void create_dive_from_plan(struct diveplan *diveplan, struct dive *dive,
 	return;
 }
 
-extern "C" void free_dps(struct diveplan *diveplan)
+void free_dps(struct diveplan *diveplan)
 {
 	if (!diveplan)
 		return;
@@ -367,7 +367,7 @@ static void add_to_end_of_diveplan(struct diveplan *diveplan, struct divedatapoi
 		dp->time += lasttime;
 }
 
-extern "C" struct divedatapoint *plan_add_segment(struct diveplan *diveplan, int duration, int depth, int cylinderid, int po2, bool entered, enum divemode_t divemode)
+struct divedatapoint *plan_add_segment(struct diveplan *diveplan, int duration, int depth, int cylinderid, int po2, bool entered, enum divemode_t divemode)
 {
 	struct divedatapoint *dp = create_dp(duration, depth, cylinderid, divemode == CCR ? po2 : 0);
 	dp->entered = entered;
@@ -501,7 +501,7 @@ static std::vector<int> sort_stops(int dstops[], size_t dnr, std::vector<gaschan
 	return stoplevels;
 }
 
-extern "C" int ascent_velocity(int depth, int avg_depth, int)
+int ascent_velocity(int depth, int avg_depth, int)
 {
 	/* We need to make this configurable */
 
@@ -1166,7 +1166,7 @@ static int get_permille(const char *begin, const char **end)
 	return value;
 }
 
-extern "C" int validate_gas(const char *text, struct gasmix *gas)
+int validate_gas(const char *text, struct gasmix *gas)
 {
 	int o2, he;
 
@@ -1213,7 +1213,7 @@ extern "C" int validate_gas(const char *text, struct gasmix *gas)
 	return 1;
 }
 
-extern "C" int validate_po2(const char *text, int *mbar_po2)
+int validate_po2(const char *text, int *mbar_po2)
 {
 	int po2;
 
diff --git a/core/planner.h b/core/planner.h
index fa285b7da..d438de1f6 100644
--- a/core/planner.h
+++ b/core/planner.h
@@ -34,8 +34,6 @@ struct diveplan {
 
 struct deco_state_cache;
 
-extern "C" {
-
 extern int validate_gas(const char *text, struct gasmix *gas);
 extern int validate_po2(const char *text, int *mbar_po2);
 extern int get_cylinderid_at_time(struct dive *dive, struct divecomputer *dc, duration_t time);
@@ -54,8 +52,6 @@ struct decostop {
 	int time;
 };
 
-}
-
 extern std::string get_planner_disclaimer_formatted();
 extern bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, int dcNr, int timestep, struct decostop *decostoptable, deco_state_cache &cache, bool is_planner, bool show_disclaimer);
 #endif // PLANNER_H
diff --git a/core/plannernotes.cpp b/core/plannernotes.cpp
index 72ee910f0..c3076c188 100644
--- a/core/plannernotes.cpp
+++ b/core/plannernotes.cpp
@@ -77,7 +77,7 @@ static std::string icd_entry(struct icd_data *icdvalues, bool printheader, int t
 	return b;
 }
 
-extern "C" const char *get_planner_disclaimer()
+const char *get_planner_disclaimer()
 {
 	return translate("gettextFromC", "DISCLAIMER / WARNING: THIS IMPLEMENTATION OF THE %s "
 			 "ALGORITHM AND A DIVE PLANNER IMPLEMENTATION BASED ON THAT HAS "
@@ -93,7 +93,7 @@ extern std::string get_planner_disclaimer_formatted()
 	return format_string_std(get_planner_disclaimer(), deco);
 }
 
-extern "C" void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_disclaimer, bool error)
+void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_disclaimer, bool error)
 {
 	std::string buf;
 	std::string icdbuf;
diff --git a/core/pref.cpp b/core/pref.cpp
index 865de9369..2a04ba7ff 100644
--- a/core/pref.cpp
+++ b/core/pref.cpp
@@ -124,7 +124,7 @@ struct preferences default_prefs = {
 };
 
 /* copy a preferences block, including making copies of all included strings */
-extern "C" void copy_prefs(struct preferences *src, struct preferences *dest)
+void copy_prefs(struct preferences *src, struct preferences *dest)
 {
 	*dest = *src;
 	dest->divelist_font = copy_string(src->divelist_font);
@@ -149,7 +149,7 @@ extern "C" void copy_prefs(struct preferences *src, struct preferences *dest)
  * These are not real leaks but they plug the holes found by eg.
  * valgrind so you can find the real leaks.
  */
-extern "C" void free_prefs(void)
+void free_prefs(void)
 {
 	// nop
 }
diff --git a/core/pref.h b/core/pref.h
index 456ca038e..214fcd551 100644
--- a/core/pref.h
+++ b/core/pref.h
@@ -5,8 +5,6 @@
 #include "units.h"
 #include "taxonomy.h"
 
-extern "C" {
-
 typedef struct
 {
 	bool po2;
@@ -224,6 +222,4 @@ extern void copy_prefs(struct preferences *src, struct preferences *dest);
 
 extern void set_informational_units(const char *units);
 
-}
-
 #endif // PREF_H
diff --git a/core/profile.cpp b/core/profile.cpp
index 36cb77645..7a2242939 100644
--- a/core/profile.cpp
+++ b/core/profile.cpp
@@ -31,7 +31,7 @@
 
 #define MAX_PROFILE_DECO 7200
 
-extern "C" int ascent_velocity(int depth, int avg_depth, int bottom_time);
+int ascent_velocity(int depth, int avg_depth, int bottom_time);
 
 #ifdef DEBUG_PI
 /* debugging tool - not normally used */
diff --git a/core/qt-ble.cpp b/core/qt-ble.cpp
index d72864add..2df255576 100644
--- a/core/qt-ble.cpp
+++ b/core/qt-ble.cpp
@@ -56,8 +56,6 @@ static std::string to_str(const T &v)
 	return v.toString().toStdString();
 }
 
-extern "C" {
-
 void BLEObject::serviceStateChanged(QLowEnergyService::ServiceState newState)
 {
 	if (verbose > 2 || debugCounter < DEBUG_THRESHOLD)
@@ -777,5 +775,3 @@ dc_status_t qt_ble_ioctl(void *io, unsigned int request, void *data, size_t size
 		return DC_STATUS_UNSUPPORTED;
 	}
 }
-
-} /* extern "C" */
diff --git a/core/qt-ble.h b/core/qt-ble.h
index 0416a51a5..d99dbadb5 100644
--- a/core/qt-ble.h
+++ b/core/qt-ble.h
@@ -67,8 +67,6 @@ private:
 	};
 };
 
-
-extern "C" {
 dc_status_t qt_ble_open(void **io, dc_context_t *context, const char *devaddr, device_data_t *user_device);
 dc_status_t qt_ble_set_timeout(void *io, int timeout);
 dc_status_t qt_ble_poll(void *io, int timeout);
@@ -76,6 +74,5 @@ dc_status_t qt_ble_read(void *io, void* data, size_t size, size_t *actual);
 dc_status_t qt_ble_write(void *io, const void* data, size_t size, size_t *actual);
 dc_status_t qt_ble_ioctl(void *io, unsigned int request, void *data, size_t size);
 dc_status_t qt_ble_close(void *io);
-}
 
 #endif
diff --git a/core/qthelper.cpp b/core/qthelper.cpp
index e09973a17..96b7d2dff 100644
--- a/core/qthelper.cpp
+++ b/core/qthelper.cpp
@@ -310,7 +310,7 @@ static xmlDocPtr get_stylesheet_doc(const xmlChar *uri, xmlDictPtr, int, void *,
 	return doc;
 }
 
-extern "C" xsltStylesheetPtr get_stylesheet(const char *name)
+xsltStylesheetPtr get_stylesheet(const char *name)
 {
 	// this needs to be done only once, but doesn't hurt to run every time
 	xsltSetLoaderFunc(get_stylesheet_doc);
@@ -363,7 +363,7 @@ std::string get_file_name(const char *fileName)
 	return fileInfo.fileName().toStdString();
 }
 
-extern "C" void copy_image_and_overwrite(const char *cfileName, const char *path, const char *cnewName)
+void copy_image_and_overwrite(const char *cfileName, const char *path, const char *cnewName)
 {
 	QString fileName(cfileName);
 	QString newName(path);
@@ -999,7 +999,7 @@ QString get_dive_date_string(timestamp_t when)
 }
 
 // Get local seconds since Epoch from ISO formatted UTC date time + offset string
-extern "C" time_t get_dive_datetime_from_isostring(char *when) {
+time_t get_dive_datetime_from_isostring(char *when) {
 	QDateTime divetime = QDateTime::fromString(when, Qt::ISODate);
 	return (time_t)(divetime.toSecsSinceEpoch());
 }
@@ -1068,7 +1068,7 @@ QString thumbnailFileName(const QString &filename)
 	return thumbnailDir() + hash.result().toHex();
 }
 
-extern "C" char *hashfile_name_string()
+char *hashfile_name_string()
 {
 	return copy_qstring(hashfile_name());
 }
@@ -1199,7 +1199,7 @@ QStringList videoExtensionFilters()
 	return filters;
 }
 
-extern "C" const char *local_file_path(struct picture *picture)
+const char *local_file_path(struct picture *picture)
 {
 	return copy_qstring(localFilePath(picture->filename));
 }
@@ -1386,14 +1386,14 @@ std::optional<std::string> getCloudURL()
 	return filename;
 }
 
-extern "C" void subsurface_mkdir(const char *dir)
+void subsurface_mkdir(const char *dir)
 {
 	QDir directory;
 	if (!directory.mkpath(QString(dir)))
 		report_info("failed to create path %s", dir);
 }
 
-extern "C" enum deco_mode decoMode(bool in_planner)
+enum deco_mode decoMode(bool in_planner)
 {
 	return in_planner ? prefs.planner_deco_mode : prefs.display_deco_mode;
 }
@@ -1553,19 +1553,19 @@ void parse_seabear_header(const char *filename, struct xml_params *params)
 	f.close();
 }
 
-extern "C" void print_qt_versions()
+void print_qt_versions()
 {
 	printf("%s\n", qPrintable(QStringLiteral("built with Qt Version %1, runtime from Qt Version %2").arg(QT_VERSION_STR).arg(qVersion())));
 }
 
 QMutex planLock;
 
-extern "C" void lock_planner()
+void lock_planner()
 {
 	planLock.lock();
 }
 
-extern "C" void unlock_planner()
+void unlock_planner()
 {
 	planLock.unlock();
 }
@@ -1626,7 +1626,7 @@ std::vector<int> get_cylinder_map_for_add(int count, int n)
 	return mapping;
 }
 
-extern "C" void emit_reset_signal()
+void emit_reset_signal()
 {
 	emit diveListNotifier.dataReset();
 }
diff --git a/core/qthelper.h b/core/qthelper.h
index 09bedabad..93e37d32c 100644
--- a/core/qthelper.h
+++ b/core/qthelper.h
@@ -2,27 +2,23 @@
 #ifndef QTHELPER_H
 #define QTHELPER_H
 
+#include "core/pref.h"
+#include "core/gettextfromc.h"
+#include "subsurface-time.h"
+#include <QString>
+#include <optional>
+#include <string>
 #include <libxslt/transform.h>
 #include <libxslt/xsltutils.h>
-#include "core/pref.h"
-#include "subsurface-time.h"
 
 struct picture;
 struct dive_trip;
 struct xml_params;
-
-// 1) Types
+struct git_info;
+class QImage;
 
 enum watertypes {FRESHWATER, BRACKISHWATER, EN13319WATER, SALTWATER, DC_WATERTYPE};
 
-// 2) Functions visible only to C++ parts
-
-#include <QString>
-#include <optional>
-#include <string>
-#include "core/gettextfromc.h"
-class QImage;
-
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
 #define SKIP_EMPTY Qt::SkipEmptyParts
 #else
@@ -111,12 +107,6 @@ std::string move_away(const std::string &path);
 #define TITLE_OR_TEXT(_t, _m) _t, _m
 #endif
 
-// 3) Functions visible to C and C++
-
-extern "C" {
-
-struct git_info;
-
 bool canReachCloudServer(struct git_info *);
 void updateWindowTitle();
 void subsurface_mkdir(const char *dir);
@@ -137,6 +127,4 @@ volume_t string_to_volume(const char *str, pressure_t workp);
 fraction_t string_to_fraction(const char *str);
 void emit_reset_signal();
 
-}
-
 #endif // QTHELPER_H
diff --git a/core/qtserialbluetooth.cpp b/core/qtserialbluetooth.cpp
index 49d077c2b..9840e1305 100644
--- a/core/qtserialbluetooth.cpp
+++ b/core/qtserialbluetooth.cpp
@@ -31,7 +31,6 @@ static std::string to_str(const T &v)
 	return v.toString().toStdString();
 }
 
-extern "C" {
 typedef struct qt_serial_t {
 	/*
 	 * RFCOMM socket used for Bluetooth Serial communication.
@@ -347,5 +346,3 @@ rfcomm_stream_open(dc_iostream_t **iostream, dc_context_t *context, const char*
 
 	return dc_custom_open (iostream, context, DC_TRANSPORT_BLUETOOTH, &callbacks, io);
 }
-
-}
diff --git a/core/sample.cpp b/core/sample.cpp
index ff2cbfa67..7a0b05d46 100644
--- a/core/sample.cpp
+++ b/core/sample.cpp
@@ -37,7 +37,7 @@ sample::sample() :
  * from the previous sample, so the indices are pre-populated (but the
  * pressures obviously are not)
  */
-extern "C" void add_sample_pressure(struct sample *sample, int sensor, int mbar)
+void add_sample_pressure(struct sample *sample, int sensor, int mbar)
 {
 	int idx;
 
diff --git a/core/sample.h b/core/sample.h
index 44e8c7c17..083700aa0 100644
--- a/core/sample.h
+++ b/core/sample.h
@@ -4,8 +4,6 @@
 
 #include "units.h"
 
-extern "C" {
-
 #define MAX_SENSORS 2
 #define MAX_O2_SENSORS 6
 #define NO_SENSOR -1
@@ -36,6 +34,4 @@ struct sample                         // BASE TYPE BYTES  UNITS    RANGE
 
 extern void add_sample_pressure(struct sample *sample, int sensor, int mbar);
 
-}
-
 #endif
diff --git a/core/save-git.cpp b/core/save-git.cpp
index c38fc1b03..fa11b18db 100644
--- a/core/save-git.cpp
+++ b/core/save-git.cpp
@@ -1105,7 +1105,7 @@ static git_tree *get_git_tree(git_repository *repo, git_object *parent)
 	return tree;
 }
 
-extern "C" int update_git_checkout(git_repository *repo, git_object *parent, git_tree *tree)
+int update_git_checkout(git_repository *repo, git_object *parent, git_tree *tree)
 {
 	git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT;
 
@@ -1116,7 +1116,7 @@ extern "C" int update_git_checkout(git_repository *repo, git_object *parent, git
 	return git_checkout_tree(repo, (git_object *) tree, &opts);
 }
 
-extern "C" int get_authorship(git_repository *repo, git_signature **authorp)
+int get_authorship(git_repository *repo, git_signature **authorp)
 {
 	if (git_signature_default(authorp, repo) == 0)
 		return 0;
diff --git a/core/save-html.h b/core/save-html.h
index af1c0ca76..e7821f36e 100644
--- a/core/save-html.h
+++ b/core/save-html.h
@@ -4,8 +4,6 @@
 
 #include "membuffer.h"
 
-extern "C" {
-
 struct dive;
 
 void put_HTML_date(struct membuffer *b, struct dive *dive, const char *pre, const char *post);
@@ -21,9 +19,6 @@ void put_HTML_volume_units(struct membuffer *b, unsigned int ml, const char *pre
 
 void export_HTML(const char *file_name, const char *photos_dir, const bool selected_only, const bool list_only);
 void export_list(struct membuffer *b, const char *photos_dir, bool selected_only, const bool list_only);
-
 void export_translation(const char *file_name);
 
-}
-
 #endif
diff --git a/core/save-profiledata.h b/core/save-profiledata.h
index 9666b544f..a2ebda068 100644
--- a/core/save-profiledata.h
+++ b/core/save-profiledata.h
@@ -2,10 +2,7 @@
 #ifndef SAVE_PROFILE_DATA_H
 #define SAVE_PROFILE_DATA_H
 
-extern "C" {
-
 int save_profiledata(const char *filename, bool selected_only);
 void save_subtitles_buffer(struct membuffer *b, struct dive *dive, int offset, int length);
 
-}
 #endif // SAVE_PROFILE_DATA_H
diff --git a/core/save-xml.cpp b/core/save-xml.cpp
index 941820be4..6d13d8bc5 100644
--- a/core/save-xml.cpp
+++ b/core/save-xml.cpp
@@ -497,7 +497,7 @@ static void save_picture(struct membuffer *b, struct picture *pic)
 	put_string(b, "/>\n");
 }
 
-extern "C" void save_one_dive_to_mb(struct membuffer *b, struct dive *dive, bool anonymize)
+void save_one_dive_to_mb(struct membuffer *b, struct dive *dive, bool anonymize)
 {
 	struct divecomputer *dc;
 	pressure_t surface_pressure = un_fixup_surface_pressure(dive);
@@ -556,7 +556,7 @@ extern "C" void save_one_dive_to_mb(struct membuffer *b, struct dive *dive, bool
 	put_format(b, "</dive>\n");
 }
 
-extern "C" int save_dive(FILE *f, struct dive *dive, bool anonymize)
+int save_dive(FILE *f, struct dive *dive, bool anonymize)
 {
 	struct membufferpp buf;
 
@@ -627,7 +627,7 @@ static void save_one_fingerprint(struct membuffer *b, int i)
 		   fp_get_data(&fingerprint_table, i).c_str());
 }
 
-extern "C" int save_dives(const char *filename)
+int save_dives(const char *filename)
 {
 	return save_dives_logic(filename, false, false);
 }
@@ -810,7 +810,7 @@ static void try_to_backup(const char *filename)
 	}
 }
 
-extern "C" int save_dives_logic(const char *filename, const bool select_only, bool anonymize)
+int save_dives_logic(const char *filename, const bool select_only, bool anonymize)
 {
 	struct membufferpp buf;
 	struct git_info info;
@@ -931,7 +931,7 @@ static void save_dive_sites_buffer(struct membuffer *b, const struct dive_site *
 	put_format(b, "</divesites>\n");
 }
 
-extern "C" int save_dive_sites_logic(const char *filename, const struct dive_site *sites[], int nr_sites, bool anonymize)
+int save_dive_sites_logic(const char *filename, const struct dive_site *sites[], int nr_sites, bool anonymize)
 {
 	struct membufferpp buf;
 	FILE *f;
diff --git a/core/selection.cpp b/core/selection.cpp
index 616ad6f5b..52178cb2e 100644
--- a/core/selection.cpp
+++ b/core/selection.cpp
@@ -14,7 +14,7 @@ struct dive *current_dive = NULL;
 int amount_selected;
 static int amount_trips_selected;
 
-extern "C" struct dive *first_selected_dive()
+struct dive *first_selected_dive()
 {
 	int idx;
 	struct dive *d;
@@ -26,7 +26,7 @@ extern "C" struct dive *first_selected_dive()
 	return NULL;
 }
 
-extern "C" struct dive *last_selected_dive()
+struct dive *last_selected_dive()
 {
 	int idx;
 	struct dive *d, *ret = NULL;
@@ -38,7 +38,7 @@ extern "C" struct dive *last_selected_dive()
 	return ret;
 }
 
-extern "C" bool consecutive_selected()
+bool consecutive_selected()
 {
 	struct dive *d;
 	int i;
@@ -63,7 +63,7 @@ extern "C" bool consecutive_selected()
 }
 
 #if DEBUG_SELECTION_TRACKING
-extern "C" void dump_selection(void)
+void dump_selection(void)
 {
 	int i;
 	struct dive *dive;
@@ -232,7 +232,7 @@ void setTripSelection(dive_trip *trip, dive *currentDive)
 	emit diveListNotifier.tripSelected(trip, currentDive);
 }
 
-extern "C" void select_single_dive(dive *d)
+void select_single_dive(dive *d)
 {
 	if (d)
 		setSelection(std::vector<dive *>{ d }, d, -1);
@@ -283,7 +283,7 @@ void updateSelection(std::vector<dive *> &selection, const std::vector<dive *> &
 }
 
 // Select the first dive that is visible
-extern "C" void select_newest_visible_dive()
+void select_newest_visible_dive()
 {
 	for (int i = divelog.dives->nr - 1; i >= 0; --i) {
 		dive *d = divelog.dives->dives[i];
@@ -295,7 +295,7 @@ extern "C" void select_newest_visible_dive()
 	select_single_dive(nullptr);
 }
 
-extern "C" void select_trip(struct dive_trip *trip)
+void select_trip(struct dive_trip *trip)
 {
 	if (trip && !trip->selected) {
 		trip->selected = true;
@@ -303,7 +303,7 @@ extern "C" void select_trip(struct dive_trip *trip)
 	}
 }
 
-extern "C" void deselect_trip(struct dive_trip *trip)
+void deselect_trip(struct dive_trip *trip)
 {
 	if (trip && trip->selected) {
 		trip->selected = false;
@@ -311,7 +311,7 @@ extern "C" void deselect_trip(struct dive_trip *trip)
 	}
 }
 
-extern "C" struct dive_trip *single_selected_trip()
+struct dive_trip *single_selected_trip()
 {
 	if (amount_trips_selected != 1)
 		return NULL;
diff --git a/core/selection.h b/core/selection.h
index 7175c9043..d21ff0a98 100644
--- a/core/selection.h
+++ b/core/selection.h
@@ -4,15 +4,14 @@
 #ifndef SELECTION_H
 #define SELECTION_H
 
+#include <vector>
+#include <QVector>
+
 struct dive;
 
 extern int amount_selected;
 extern struct dive *current_dive;
 
-/*** C and C++ functions ***/
-
-extern "C" {
-
 extern struct dive *first_selected_dive(void);
 extern struct dive *last_selected_dive(void);
 extern bool consecutive_selected(void);
@@ -27,13 +26,6 @@ extern void clear_selection(void);
 extern void dump_selection(void);
 #endif
 
-}
-
-/*** C++-only functions ***/
-
-#include <vector>
-#include <QVector>
-
 // Reset the selection to the dives of the "selection" vector and send the appropriate signals.
 // Set the current dive to "currentDive" and the current dive computer to "currentDc".
 // "currentDive" must be an element of "selection" (or null if "seletion" is empty).
diff --git a/core/ssrf.h b/core/ssrf.h
index 78c4e951e..feed74a52 100644
--- a/core/ssrf.h
+++ b/core/ssrf.h
@@ -2,15 +2,11 @@
 #ifndef SSRF_H
 #define SSRF_H
 
-extern "C" {
-
 #ifdef __clang__
 // Clang has a bug on zero-initialization of C structs.
 #pragma clang diagnostic ignored "-Wmissing-field-initializers"
 #endif
 
-}
-
 // Macro to be used for silencing unused parameters
 #define UNUSED(x) (void)x
 
diff --git a/core/strtod.cpp b/core/strtod.cpp
index e76ee47c0..39abfb7a7 100644
--- a/core/strtod.cpp
+++ b/core/strtod.cpp
@@ -109,12 +109,12 @@ no_conversion:
 	return 0.0;
 }
 
-extern "C" double permissive_strtod(const char *str, const char **ptr)
+double permissive_strtod(const char *str, const char **ptr)
 {
 	return strtod_flags(str, ptr, false);
 }
 
-extern "C" double ascii_strtod(const char *str, const char **ptr)
+double ascii_strtod(const char *str, const char **ptr)
 {
 	return strtod_flags(str, ptr, true);
 }
diff --git a/core/subsurface-string.h b/core/subsurface-string.h
index 61c70d71a..80a6f7bab 100644
--- a/core/subsurface-string.h
+++ b/core/subsurface-string.h
@@ -9,8 +9,6 @@
 #include <string_view>
 #include <vector>
 
-extern "C" {
-
 // string handling
 
 static inline bool same_string(const char *a, const char *b)
@@ -36,8 +34,6 @@ static inline char *copy_string(const char *s)
 extern double permissive_strtod(const char *str, const char **ptr);
 extern double ascii_strtod(const char *str, const char **ptr);
 
-}
-
 // Sadly, starts_with only with C++20!
 inline bool starts_with(std::string_view s, const char *s2)
 {
diff --git a/core/subsurface-time.h b/core/subsurface-time.h
index 14a77bf20..06efad307 100644
--- a/core/subsurface-time.h
+++ b/core/subsurface-time.h
@@ -6,8 +6,6 @@
 #include <string>
 #include <time.h>
 
-extern "C" {
-
 extern timestamp_t utc_mktime(const struct tm *tm);
 extern void utc_mkdate(timestamp_t, struct tm *tm);
 extern int utc_year(timestamp_t timestamp);
@@ -15,11 +13,8 @@ extern int utc_weekday(timestamp_t timestamp);
 
 /* parse and format date times of the form YYYY-MM-DD hh:mm:ss */
 extern timestamp_t parse_datetime(const char *s); /* returns 0 on error */
-
 extern const char *monthname(int mon);
 
-}
-
 std::string format_datetime(timestamp_t timestamp); /* ownership of string passed to caller */
 
 #endif
diff --git a/core/subsurfacestartup.cpp b/core/subsurfacestartup.cpp
index e91a340bc..86d600109 100644
--- a/core/subsurfacestartup.cpp
+++ b/core/subsurfacestartup.cpp
@@ -25,7 +25,7 @@ std::string testqml;
  */
 bool imported = false;
 
-extern "C" void print_version()
+void print_version()
 {
 	static bool version_printed = false;
 	if (version_printed)
@@ -43,7 +43,7 @@ extern "C" void print_version()
 	version_printed = true;
 }
 
-extern "C" void print_files()
+void print_files()
 {
 	struct git_info info;
 	std::optional<std::string> filename;
@@ -89,7 +89,7 @@ static void print_help()
 	printf("\n --cloud-timeout=<nr>  Set timeout for cloud connection (0 < timeout < 60)\n\n");
 }
 
-extern "C" void parse_argument(const char *arg)
+void parse_argument(const char *arg)
 {
 	const char *p = arg + 1;
 
@@ -191,7 +191,7 @@ extern "C" void parse_argument(const char *arg)
  * I guess Burma and Liberia should trigger this too. I'm too
  * lazy to look up the territory names, though.
  */
-extern "C" void setup_system_prefs(void)
+void setup_system_prefs(void)
 {
 	const char *env;
 
diff --git a/core/subsurfacestartup.h b/core/subsurfacestartup.h
index 38028c71b..ddb18b53f 100644
--- a/core/subsurfacestartup.h
+++ b/core/subsurfacestartup.h
@@ -2,8 +2,6 @@
 #ifndef SUBSURFACESTARTUP_H
 #define SUBSURFACESTARTUP_H
 
-extern "C" {
-
 extern bool imported;
 extern int quit, force_root, ignore_bt;
 
@@ -15,8 +13,6 @@ void print_version(void);
 
 extern char *settings_suffix;
 
-}
-
 #ifdef SUBSURFACE_MOBILE_DESKTOP
 #include <string>
 extern std::string testqml;
diff --git a/core/subsurfacesysinfo.cpp b/core/subsurfacesysinfo.cpp
index 7cad562b8..966c528a0 100644
--- a/core/subsurfacesysinfo.cpp
+++ b/core/subsurfacesysinfo.cpp
@@ -3,7 +3,7 @@
 #include <QSysInfo>
 
 #ifdef Q_OS_WIN
-extern "C" bool isWin7Or8()
+bool isWin7Or8()
 {
 	return (QSysInfo::WindowsVersion & QSysInfo::WV_NT_based) >= QSysInfo::WV_WINDOWS7;
 }
diff --git a/core/subsurfacesysinfo.h b/core/subsurfacesysinfo.h
index 46566a6d5..a5354478a 100644
--- a/core/subsurfacesysinfo.h
+++ b/core/subsurfacesysinfo.h
@@ -1,11 +1,7 @@
 #ifndef SUBSURFACESYSINFO_H
 #define SUBSURFACESYSINFO_H
 
-#include <QtGlobal>
-
 #ifdef Q_OS_WIN
-extern "C"
-
 bool isWin7Or8();
 #endif
 
diff --git a/core/tag.cpp b/core/tag.cpp
index 3dca51b2e..50b588f74 100644
--- a/core/tag.cpp
+++ b/core/tag.cpp
@@ -39,7 +39,7 @@ static bool tag_seen_before(struct tag_entry *start, struct tag_entry *before)
 }
 
 /* remove duplicates and empty nodes */
-extern "C" void taglist_cleanup(struct tag_entry **tag_list)
+void taglist_cleanup(struct tag_entry **tag_list)
 {
 	struct tag_entry **tl = tag_list;
 	while (*tl) {
@@ -105,7 +105,7 @@ static const divetag *register_tag(const char *s, const char *source)
 	return it->get();
 }
 
-extern "C" void taglist_add_tag(struct tag_entry **tag_list, const char *tag)
+void taglist_add_tag(struct tag_entry **tag_list, const char *tag)
 {
 	bool is_default_tag = std::find_if(std::begin(default_tags), std::end(default_tags),
 			[&tag] (const char *default_tag) { return tag == default_tag; });
@@ -119,12 +119,12 @@ extern "C" void taglist_add_tag(struct tag_entry **tag_list, const char *tag)
 	taglist_add_divetag(tag_list, d_tag);
 }
 
-extern "C" void taglist_free(struct tag_entry *entry)
+void taglist_free(struct tag_entry *entry)
 {
 	STRUCTURED_LIST_FREE(struct tag_entry, entry, free)
 }
 
-extern "C" struct tag_entry *taglist_copy(struct tag_entry *s)
+struct tag_entry *taglist_copy(struct tag_entry *s)
 {
 	struct tag_entry *res;
 	STRUCTURED_LIST_COPY(struct tag_entry, s, res, copy_tl);
@@ -132,7 +132,7 @@ extern "C" struct tag_entry *taglist_copy(struct tag_entry *s)
 }
 
 /* Merge src1 and src2, write to *dst */
-extern "C" void taglist_merge(struct tag_entry **dst, struct tag_entry *src1, struct tag_entry *src2)
+void taglist_merge(struct tag_entry **dst, struct tag_entry *src1, struct tag_entry *src2)
 {
 	struct tag_entry *entry;
 
@@ -142,7 +142,7 @@ extern "C" void taglist_merge(struct tag_entry **dst, struct tag_entry *src1, st
 		taglist_add_divetag(dst, entry->tag);
 }
 
-extern "C" void taglist_init_global()
+void taglist_init_global()
 {
 	for (const char *s: default_tags)
 		register_tag(translate("gettextFromC", s), s);
diff --git a/core/tag.h b/core/tag.h
index dd3bf10d2..a4c8fa689 100644
--- a/core/tag.h
+++ b/core/tag.h
@@ -6,8 +6,7 @@
 #include <memory>
 #include <string>
 #include <vector>
-
-extern "C" {
+#include <string>
 
 struct divetag {
 	/*
@@ -54,12 +53,6 @@ extern std::vector<std::unique_ptr<divetag>> g_tag_list;
  */
 extern std::string taglist_get_tagstring(struct tag_entry *tag_list);
 
-}
-
-// C++ only functions
-
-#include <string>
-
 /* Comma separated list of tags names or null terminated string */
 std::string taglist_get_tagstring(struct tag_entry *tag_list);
 
diff --git a/core/time.cpp b/core/time.cpp
index bf42554a6..03b5e3082 100644
--- a/core/time.cpp
+++ b/core/time.cpp
@@ -33,7 +33,7 @@
  * are unnecessary once you're counting minutes (32-bit minutes:
  * 8000+ years).
  */
-extern "C" void utc_mkdate(timestamp_t timestamp, struct tm *tm)
+void utc_mkdate(timestamp_t timestamp, struct tm *tm)
 {
 	static const unsigned int mdays[] = {
 		31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
@@ -100,7 +100,7 @@ extern "C" void utc_mkdate(timestamp_t timestamp, struct tm *tm)
 	tm->tm_mon = m;
 }
 
-extern "C" timestamp_t utc_mktime(const struct tm *tm)
+timestamp_t utc_mktime(const struct tm *tm)
 {
 	static const int mdays[] = {
 		0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
@@ -147,7 +147,7 @@ extern "C" timestamp_t utc_mktime(const struct tm *tm)
  * out unused calculations. If it turns out to be a bottle neck
  * we will have to cache a struct tm per dive.
  */
-extern "C" int utc_year(timestamp_t timestamp)
+int utc_year(timestamp_t timestamp)
 {
 	struct tm tm;
 	utc_mkdate(timestamp, &tm);
@@ -162,7 +162,7 @@ extern "C" int utc_year(timestamp_t timestamp)
  * at throwing out unused calculations, so this is more efficient
  * than it looks.
  */
-extern "C" int utc_weekday(timestamp_t timestamp)
+int utc_weekday(timestamp_t timestamp)
 {
 	struct tm tm;
 	utc_mkdate(timestamp, &tm);
@@ -174,7 +174,7 @@ extern "C" int utc_weekday(timestamp_t timestamp)
  * an 64-bit decimal and return 64-bit timestamp. On failure or
  * if passed an empty string, return 0.
  */
-extern "C" timestamp_t parse_datetime(const char *s)
+timestamp_t parse_datetime(const char *s)
 {
 	int y, m, d;
 	int hr, min, sec;
diff --git a/core/trip.h b/core/trip.h
index ec6e743b9..cb4a8da0f 100644
--- a/core/trip.h
+++ b/core/trip.h
@@ -4,8 +4,6 @@
 
 #include "divelist.h"
 
-extern "C" {
-
 typedef struct dive_trip
 {
 	char *location;
@@ -58,8 +56,6 @@ void clear_trip_table(struct trip_table *table);
 extern void dump_trip_list(void);
 #endif
 
-}
-
 /* Make pointers to dive_trip and trip_table "Qt metatypes" so that they can be
  * passed through QVariants and through QML. See comment in dive.h. */
 #include <QObject>
diff --git a/core/units.cpp b/core/units.cpp
index 142bfbb47..a589c3ca4 100644
--- a/core/units.cpp
+++ b/core/units.cpp
@@ -9,7 +9,7 @@ const struct units IMPERIAL_units = {
 	.vertical_speed_time = units::MINUTES, .duration_units = units::MIXED, .show_units_table = false
 };
 
-extern "C" int get_pressure_units(int mb, const char **units)
+int get_pressure_units(int mb, const char **units)
 {
 	int pressure;
 	const char *unit;
@@ -31,7 +31,7 @@ extern "C" int get_pressure_units(int mb, const char **units)
 	return pressure;
 }
 
-extern "C" double get_temp_units(unsigned int mk, const char **units)
+double get_temp_units(unsigned int mk, const char **units)
 {
 	double deg;
 	const char *unit;
@@ -49,7 +49,7 @@ extern "C" double get_temp_units(unsigned int mk, const char **units)
 	return deg;
 }
 
-extern "C" double get_volume_units(unsigned int ml, int *frac, const char **units)
+double get_volume_units(unsigned int ml, int *frac, const char **units)
 {
 	int decimals;
 	double vol;
@@ -76,7 +76,7 @@ extern "C" double get_volume_units(unsigned int ml, int *frac, const char **unit
 	return vol;
 }
 
-extern "C" int units_to_sac(double volume)
+int units_to_sac(double volume)
 {
 	if (get_units()->volume == units::CUFT)
 		return lrint(cuft_to_l(volume) * 1000.0);
@@ -84,7 +84,7 @@ extern "C" int units_to_sac(double volume)
 		return lrint(volume * 1000);
 }
 
-extern "C" depth_t units_to_depth(double depth)
+depth_t units_to_depth(double depth)
 {
 	depth_t internaldepth;
 	if (get_units()->length == units::METERS) {
@@ -95,7 +95,7 @@ extern "C" depth_t units_to_depth(double depth)
 	return internaldepth;
 }
 
-extern "C" double get_depth_units(int mm, int *frac, const char **units)
+double get_depth_units(int mm, int *frac, const char **units)
 {
 	int decimals;
 	double d;
@@ -122,7 +122,7 @@ extern "C" double get_depth_units(int mm, int *frac, const char **units)
 	return d;
 }
 
-extern "C" double get_vertical_speed_units(unsigned int mms, int *frac, const char **units)
+double get_vertical_speed_units(unsigned int mms, int *frac, const char **units)
 {
 	double d;
 	const char *unit;
@@ -153,7 +153,7 @@ extern "C" double get_vertical_speed_units(unsigned int mms, int *frac, const ch
 	return d;
 }
 
-extern "C" double get_weight_units(unsigned int grams, int *frac, const char **units)
+double get_weight_units(unsigned int grams, int *frac, const char **units)
 {
 	int decimals;
 	double value;
@@ -176,7 +176,7 @@ extern "C" double get_weight_units(unsigned int grams, int *frac, const char **u
 	return value;
 }
 
-extern "C" const struct units *get_units()
+const struct units *get_units()
 {
 	return &prefs.units;
 }
diff --git a/core/units.h b/core/units.h
index 9a4c98f24..c1c68cc59 100644
--- a/core/units.h
+++ b/core/units.h
@@ -7,8 +7,6 @@
 #define M_PI 3.14159265358979323846
 #endif
 
-extern "C" {
-
 #define FRACTION_TUPLE(n, x) ((unsigned)(n) / (x)), ((unsigned)(n) % (x))
 #define SIGNED_FRAC_TRIPLET(n, x) ((n) >= 0 ? '+': '-'), ((n) >= 0 ? (unsigned)(n) / (x) : (-(n) / (x))), ((unsigned)((n) >= 0 ? (n) : -(n)) % (x))
 
@@ -338,6 +336,5 @@ extern double get_vertical_speed_units(unsigned int mms, int *frac, const char *
 
 extern depth_t units_to_depth(double depth);
 extern int units_to_sac(double volume);
-}
 
 #endif
diff --git a/core/unix.cpp b/core/unix.cpp
index c0b288cc2..dcae486a3 100644
--- a/core/unix.cpp
+++ b/core/unix.cpp
@@ -35,8 +35,6 @@ static std::string make_default_filename()
 	return system_default_path() + "/" + user + ".xml";
 }
 
-extern "C" {
-
 // the DE should provide us with a default font and font size...
 const char unix_system_divelist_default_font[] = "Sans";
 const char *system_divelist_default_font = unix_system_divelist_default_font;
@@ -203,5 +201,3 @@ bool subsurface_user_is_root()
 {
 	return geteuid() == 0;
 }
-
-}
diff --git a/core/version.cpp b/core/version.cpp
index bf1bcefb0..811e763b8 100644
--- a/core/version.cpp
+++ b/core/version.cpp
@@ -2,12 +2,12 @@
 #include "ssrf-version.h"
 
 // let's leave the two redundant functions in case we change our minds on git SHAs
-extern "C" const char *subsurface_git_version(void)
+const char *subsurface_git_version(void)
 {
 	return CANONICAL_VERSION_STRING_4;
 }
 
-extern "C" const char *subsurface_canonical_version(void)
+const char *subsurface_canonical_version(void)
 {
 	return CANONICAL_VERSION_STRING;
 }
diff --git a/core/version.h b/core/version.h
index a37ec596f..148f2d559 100644
--- a/core/version.h
+++ b/core/version.h
@@ -1,11 +1,7 @@
 #ifndef VERSION_H
 #define VERSION_H
 
-extern "C" {
-
 const char *subsurface_git_version(void);
 const char *subsurface_canonical_version(void);
 
-}
-
 #endif
diff --git a/core/webservice.h b/core/webservice.h
index f31d0d007..4831072dd 100644
--- a/core/webservice.h
+++ b/core/webservice.h
@@ -2,8 +2,6 @@
 #ifndef WEBSERVICE_H
 #define WEBSERVICE_H
 
-extern "C" {
-
 //extern void webservice_download_dialog(void);
 //extern bool webservice_request_user_xml(const gchar *, gchar **, unsigned int *, unsigned int *);
 extern int divelogde_upload(char *fn, char **error);
@@ -16,6 +14,4 @@ enum {
 	DD_STATUS_ERROR_PARSE,
 };
 
-
-}
 #endif // WEBSERVICE_H
diff --git a/core/windows.cpp b/core/windows.cpp
index 76a37fe6a..c244cfc5a 100644
--- a/core/windows.cpp
+++ b/core/windows.cpp
@@ -100,8 +100,6 @@ static std::wstring make_default_filename()
 	return path + L"\\" + filename;
 }
 
-extern "C" {
-
 const char non_standard_system_divelist_default_font[] = "Calibri";
 const char current_system_divelist_default_font[] = "Segoe UI";
 const char *system_divelist_default_font = non_standard_system_divelist_default_font;
@@ -427,5 +425,3 @@ bool subsurface_user_is_root()
 	/* FIXME: Detect admin rights */
 	return false;
 }
-
-}
diff --git a/core/windowtitleupdate.cpp b/core/windowtitleupdate.cpp
index a0cc277b3..a6c5f2425 100644
--- a/core/windowtitleupdate.cpp
+++ b/core/windowtitleupdate.cpp
@@ -3,7 +3,7 @@
 
 WindowTitleUpdate windowTitleUpdate;
 
-extern "C" void updateWindowTitle()
+void updateWindowTitle()
 {
 	emit windowTitleUpdate.updateTitle();
 }
diff --git a/core/worldmap-save.cpp b/core/worldmap-save.cpp
index 8bfa14d66..803c3cb32 100644
--- a/core/worldmap-save.cpp
+++ b/core/worldmap-save.cpp
@@ -106,7 +106,7 @@ static void export_doit(struct membuffer *b, const bool selected_only)
 	put_string(b, "\t</head>\n<body>\n<div id=\"map-canvas\"></div>\n</body>\n</html>");
 }
 
-extern "C" void export_worldmap_HTML(const char *file_name, const bool selected_only)
+void export_worldmap_HTML(const char *file_name, const bool selected_only)
 {
 	FILE *f;
 
diff --git a/core/worldmap-save.h b/core/worldmap-save.h
index 46d580f59..5b83b4bb9 100644
--- a/core/worldmap-save.h
+++ b/core/worldmap-save.h
@@ -2,10 +2,6 @@
 #ifndef WORLDMAP_SAVE_H
 #define WORLDMAP_SAVE_H
 
-extern "C" {
-
 extern void export_worldmap_HTML(const char *file_name, bool selected_only);
 
-}
-
 #endif
diff --git a/core/xmlparams.cpp b/core/xmlparams.cpp
index a12739a4d..3ab6f1c4c 100644
--- a/core/xmlparams.cpp
+++ b/core/xmlparams.cpp
@@ -1,42 +1,42 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "xmlparams.h"
 
-extern "C" struct xml_params *alloc_xml_params()
+struct xml_params *alloc_xml_params()
 {
 	return new xml_params;
 }
 
-extern "C" void free_xml_params(struct xml_params *params)
+void free_xml_params(struct xml_params *params)
 {
 	delete params;
 }
 
-extern "C" void xml_params_resize(struct xml_params *params, int count)
+void xml_params_resize(struct xml_params *params, int count)
 {
 	params->items.resize(count);
 }
 
-extern "C" void xml_params_add(struct xml_params *params, const char *key, const char *value)
+void xml_params_add(struct xml_params *params, const char *key, const char *value)
 {
 	params->items.push_back({ std::string(key), std::string(value) });
 }
 
-extern "C" void xml_params_add_int(struct xml_params *params, const char *key, int value)
+void xml_params_add_int(struct xml_params *params, const char *key, int value)
 {
 	params->items.push_back({ std::string(key), std::to_string(value) });
 }
 
-extern "C" int xml_params_count(const struct xml_params *params)
+int xml_params_count(const struct xml_params *params)
 {
 	return (int)params->items.size();
 }
 
-extern "C" const char *xml_params_get_key(const struct xml_params *params, int idx)
+const char *xml_params_get_key(const struct xml_params *params, int idx)
 {
 	return params->items[idx].first.c_str();
 }
 
-extern "C" const char *xml_params_get_value(const struct xml_params *params, int idx)
+const char *xml_params_get_value(const struct xml_params *params, int idx)
 {
 	return params->items[idx].second.c_str();
 }
@@ -48,7 +48,7 @@ extern void xml_params_set_value(struct xml_params *params, int idx, const char
 	params->items[idx].second = value;
 }
 
-extern "C" const char **xml_params_get(const struct xml_params *params)
+const char **xml_params_get(const struct xml_params *params)
 {
 	if (!params)
 		return nullptr;
diff --git a/core/xmlparams.h b/core/xmlparams.h
index 0631d3214..e91a30ce0 100644
--- a/core/xmlparams.h
+++ b/core/xmlparams.h
@@ -12,8 +12,6 @@ struct xml_params {
 	mutable std::vector<const char *> data;
 };
 
-extern "C" {
-
 // Return values marked as "not stable" may be invalidated when calling
 // an xml_params_*() function that takes a non-const xml_params parameter.
 extern struct xml_params *alloc_xml_params();
@@ -27,6 +25,4 @@ extern const char *xml_params_get_value(const struct xml_params *params, int idx
 extern void xml_params_set_value(struct xml_params *params, int idx, const char *value);
 extern const char **xml_params_get(const struct xml_params *params); // not stable
 
-}
-
 #endif
diff --git a/desktop-widgets/mainwindow.cpp b/desktop-widgets/mainwindow.cpp
index 7a5c9a7db..d5587c0f4 100644
--- a/desktop-widgets/mainwindow.cpp
+++ b/desktop-widgets/mainwindow.cpp
@@ -82,7 +82,7 @@ namespace {
 	int progressCounter = 0;
 }
 
-extern "C" int updateProgress(const char *text)
+int updateProgress(const char *text)
 {
 	if (verbose)
 		report_info("git storage: %s", text);
@@ -107,7 +107,7 @@ extern "C" int updateProgress(const char *text)
 
 MainWindow *MainWindow::m_Instance = nullptr;
 
-extern "C" void showErrorFromC(char *buf)
+void showErrorFromC(char *buf)
 {
 	QString error(buf);
 	free(buf);
diff --git a/desktop-widgets/profilewidget.h b/desktop-widgets/profilewidget.h
index b55e0e6a9..272d1a529 100644
--- a/desktop-widgets/profilewidget.h
+++ b/desktop-widgets/profilewidget.h
@@ -15,8 +15,6 @@ class ProfileWidget2;
 class EmptyView;
 class QStackedWidget;
 
-extern "C" void free_dive(struct dive *);
-
 class ProfileWidget : public QWidget {
 	Q_OBJECT
 public:
diff --git a/mobile-widgets/qmlmanager.cpp b/mobile-widgets/qmlmanager.cpp
index 2027a673b..fcdfe7135 100644
--- a/mobile-widgets/qmlmanager.cpp
+++ b/mobile-widgets/qmlmanager.cpp
@@ -66,7 +66,7 @@ bool noCloudToCloud = false;
 #define RED_FONT QLatin1String("<font color=\"red\">")
 #define END_FONT QLatin1String("</font>")
 
-extern "C" void showErrorFromC(char *buf)
+void showErrorFromC(char *buf)
 {
 	QString error(buf);
 	free(buf);
@@ -124,7 +124,7 @@ static void showProgress(QString msg)
 }
 
 // show the git progress in the passive notification area
-extern "C" int gitProgressCB(const char *text)
+int gitProgressCB(const char *text)
 {
 	// regular users, during regular operation, likely really don't
 	// care at all about the git progress
diff --git a/smtk-import/smartrak.cpp b/smtk-import/smartrak.cpp
index 4d48bb46c..d8ff9258b 100644
--- a/smtk-import/smartrak.cpp
+++ b/smtk-import/smartrak.cpp
@@ -874,7 +874,7 @@ static dc_status_t libdc_buffer_complete(device_data_t *dev_data, unsigned char
  * a DB clone is necessary as calling mdb_fetch_row() over different tables in
  * a single DB breaks binded row data, and so would break the top loop.
  */
-extern "C" void smartrak_import(const char *file, struct divelog *log)
+void smartrak_import(const char *file, struct divelog *log)
 {
 	MdbHandle *mdb, *mdb_clon;
 	MdbColumn *col[MDB_MAX_COLS];
diff --git a/smtk-import/smrtk2ssrfc_window.cpp b/smtk-import/smrtk2ssrfc_window.cpp
index 78b9ef1c3..c80853814 100644
--- a/smtk-import/smrtk2ssrfc_window.cpp
+++ b/smtk-import/smrtk2ssrfc_window.cpp
@@ -15,7 +15,7 @@ QStringList inputFiles;
 QString outputFile;
 QString error_buf;
 
-extern "C" void getErrorFromC(char *buf)
+void getErrorFromC(char *buf)
 {
 	QString error(buf);
 	free(buf);
diff --git a/smtk-import/smrtk2ssrfc_window.h b/smtk-import/smrtk2ssrfc_window.h
index d17f8d098..5998f935a 100644
--- a/smtk-import/smrtk2ssrfc_window.h
+++ b/smtk-import/smrtk2ssrfc_window.h
@@ -7,7 +7,7 @@
 #include <QFileInfo>
 
 struct divelog;
-extern "C" void smartrak_import(const char *file, struct divelog *log);
+void smartrak_import(const char *file, struct divelog *log);
 
 namespace Ui {
 class Smrtk2ssrfcWindow;