From 28520da65574866cdd7cf0d0ed8f0c062970cdb6 Mon Sep 17 00:00:00 2001
From: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
Date: Tue, 28 May 2024 21:31:11 +0200
Subject: [PATCH] core: convert cylinder_t and cylinder_table to C++

This had to be done simultaneously, because the table macros
do not work properly with C++ objects.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
---
 backend-shared/exportfuncs.cpp                |   8 +-
 commands/command_divelist.cpp                 |   2 +-
 commands/command_edit.cpp                     |  52 ++--
 core/cochran.cpp                              |  15 +-
 core/datatrak.cpp                             |  13 +-
 core/dive.cpp                                 | 255 ++++++++----------
 core/dive.h                                   |   5 +-
 core/divelist.cpp                             |  21 +-
 core/equipment.cpp                            | 200 +++++++-------
 core/equipment.h                              |  37 +--
 core/filterconstraint.cpp                     |  21 +-
 core/fulltext.cpp                             |   6 +-
 core/gas.cpp                                  |  12 +-
 core/gas.h                                    |   2 +-
 core/gaspressures.cpp                         |   4 +-
 core/import-csv.cpp                           |  45 ++--
 core/import-divinglog.cpp                     |   2 +-
 core/import-shearwater.cpp                    |  21 +-
 core/libdivecomputer.cpp                      |  10 +-
 core/liquivision.cpp                          |   3 +-
 core/load-git.cpp                             |   8 +-
 core/parse-xml.cpp                            |  25 +-
 core/parse.cpp                                |   2 +-
 core/planner.cpp                              |  18 +-
 core/plannernotes.cpp                         |  44 +--
 core/profile.cpp                              |  35 ++-
 core/profile.h                                |   2 +-
 core/qthelper.cpp                             |  13 +-
 core/save-git.cpp                             |  25 +-
 core/save-html.cpp                            |  33 ++-
 core/save-xml.cpp                             |  26 +-
 core/statistics.cpp                           |  27 +-
 core/string-format.cpp                        |  78 +++---
 core/uemis.cpp                                |   2 +-
 desktop-widgets/profilewidget.cpp             |   2 +-
 desktop-widgets/simplewidgets.cpp             |   8 +-
 .../tab-widgets/TabDiveInformation.cpp        |   8 +-
 desktop-widgets/templatelayout.cpp            |   8 +-
 mobile-widgets/qmlmanager.cpp                 |   2 +-
 profile-widget/diveprofileitem.cpp            |   7 +-
 profile-widget/profilewidget2.cpp             |  28 +-
 profile-widget/tankitem.cpp                   |   2 +-
 qt-models/cylindermodel.cpp                   |  73 +++--
 qt-models/diveplannermodel.cpp                |  22 +-
 qt-models/divesummarymodel.cpp                |   9 +-
 qt-models/divetripmodel.cpp                   |  19 +-
 smtk-import/smartrak.cpp                      |  15 +-
 stats/statsvariables.cpp                      |  28 +-
 48 files changed, 593 insertions(+), 710 deletions(-)

diff --git a/backend-shared/exportfuncs.cpp b/backend-shared/exportfuncs.cpp
index 65bf89155..6a3bf1c96 100644
--- a/backend-shared/exportfuncs.cpp
+++ b/backend-shared/exportfuncs.cpp
@@ -205,10 +205,10 @@ void export_TeX(const char *filename, bool selected_only, bool plain, ExportCall
 		// Print cylinder data
 		put_format(&buf, "\n%% Gas use information:\n");
 		qty_cyl = 0;
-		for (i = 0; i < dive->cylinders.nr; i++){
-			const cylinder_t &cyl = *get_cylinder(dive, i);
-			if (is_cylinder_used(dive, i) || (prefs.include_unused_tanks && cyl.type.description)){
-				put_format(&buf, "\\def\\%scyl%cdescription{%s}\n", ssrf, 'a' + i, cyl.type.description);
+		for (int i = 0; i < static_cast<int>(dive->cylinders.size()); i++){
+			const cylinder_t &cyl = dive->cylinders[i];
+			if (is_cylinder_used(dive, i) || (prefs.include_unused_tanks && !cyl.type.description.empty())){
+				put_format(&buf, "\\def\\%scyl%cdescription{%s}\n", ssrf, 'a' + i, cyl.type.description.c_str());
 				put_format(&buf, "\\def\\%scyl%cgasname{%s}\n", ssrf, 'a' + i, gasname(cyl.gasmix));
 				put_format(&buf, "\\def\\%scyl%cmixO2{%.1f\\%%}\n", ssrf, 'a' + i, get_o2(cyl.gasmix)/10.0);
 				put_format(&buf, "\\def\\%scyl%cmixHe{%.1f\\%%}\n", ssrf, 'a' + i, get_he(cyl.gasmix)/10.0);
diff --git a/commands/command_divelist.cpp b/commands/command_divelist.cpp
index 49f16b8bd..f745f2955 100644
--- a/commands/command_divelist.cpp
+++ b/commands/command_divelist.cpp
@@ -962,7 +962,7 @@ MergeDives::MergeDives(const QVector <dive *> &dives)
 {
 	setText(Command::Base::tr("merge dive"));
 
-	// Just a safety check - if there's not two or more dives - do nothing
+	// Just a safety check - if there's not two or more dives - do nothing.
 	// The caller should have made sure that this doesn't happen.
 	if (dives.count() < 2) {
 		qWarning("Merging less than two dives");
diff --git a/commands/command_edit.cpp b/commands/command_edit.cpp
index 5d5976068..1864588ed 100644
--- a/commands/command_edit.cpp
+++ b/commands/command_edit.cpp
@@ -629,7 +629,6 @@ static void swapCandQString(QString &q, char *&c)
 PasteState::PasteState(dive *dIn, const dive *data, dive_components what) : d(dIn),
 	tags(nullptr)
 {
-	memset(&cylinders, 0, sizeof(cylinders));
 	memset(&weightsystems, 0, sizeof(weightsystems));
 	if (what.notes)
 		notes = data->notes;
@@ -656,14 +655,14 @@ PasteState::PasteState(dive *dIn, const dive *data, dive_components what) : d(dI
 	if (what.tags)
 		tags = taglist_copy(data->tag_list);
 	if (what.cylinders) {
-		copy_cylinders(&data->cylinders, &cylinders);
+		cylinders = data->cylinders;
 		// Paste cylinders is "special":
 		// 1) For cylinders that exist in the destination dive we keep the gas-mix and pressures.
 		// 2) For cylinders that do not yet exist in the destination dive, we set the pressures to 0, i.e. unset.
 		//    Moreover, for these we set the manually_added flag, because they weren't downloaded from a DC.
-		for (int i = 0; i < d->cylinders.nr && i < cylinders.nr; ++i) {
-			const cylinder_t &src = *get_cylinder(d, i);
-			cylinder_t &dst = cylinders.cylinders[i];
+		for (size_t i = 0; i < d->cylinders.size() && i < cylinders.size(); ++i) {
+			const cylinder_t &src = d->cylinders[i];
+			cylinder_t &dst = cylinders[i];
 			dst.gasmix = src.gasmix;
 			dst.start = src.start;
 			dst.end = src.end;
@@ -677,8 +676,8 @@ PasteState::PasteState(dive *dIn, const dive *data, dive_components what) : d(dI
 			dst.bestmix_o2 = src.bestmix_o2;
 			dst.bestmix_he = src.bestmix_he;
 		}
-		for (int i = d->cylinders.nr; i < cylinders.nr; ++i) {
-			cylinder_t &cyl = cylinders.cylinders[i];
+		for (size_t i = d->cylinders.size(); i < cylinders.size(); ++i) {
+			cylinder_t &cyl = cylinders[i];
 			cyl.start.mbar = 0;
 			cyl.end.mbar = 0;
 			cyl.sample_start.mbar = 0;
@@ -697,7 +696,6 @@ PasteState::PasteState(dive *dIn, const dive *data, dive_components what) : d(dI
 PasteState::~PasteState()
 {
 	taglist_free(tags);
-	clear_cylinder_table(&cylinders);
 	clear_weightsystem_table(&weightsystems);
 	free(weightsystems.weightsystems);
 }
@@ -803,7 +801,6 @@ ReplanDive::ReplanDive(dive *source) : d(current_dive),
 	duration({0}),
 	salinity(0)
 {
-	memset(&cylinders, 0, sizeof(cylinders));
 	if (!d)
 		return;
 
@@ -828,7 +825,6 @@ ReplanDive::ReplanDive(dive *source) : d(current_dive),
 
 ReplanDive::~ReplanDive()
 {
-	clear_cylinder_table(&cylinders);
 	free(notes);
 }
 
@@ -1124,7 +1120,6 @@ AddCylinder::AddCylinder(bool currentDiveOnly) :
 
 AddCylinder::~AddCylinder()
 {
-	free_cylinder(cyl);
 }
 
 bool AddCylinder::workToBeDone()
@@ -1148,7 +1143,7 @@ void AddCylinder::redo()
 	for (dive *d: dives) {
 		int index = first_hidden_cylinder(d);
 		indexes.push_back(index);
-		add_cylinder(&d->cylinders, index, clone_cylinder(cyl));
+		add_cylinder(&d->cylinders, index, cyl);
 		update_cylinder_related_info(d);
 		emit diveListNotifier.cylinderAdded(d, index);
 		invalidate_dive_cache(d); // Ensure that dive is written in git_save()
@@ -1157,14 +1152,14 @@ void AddCylinder::redo()
 
 static bool same_cylinder_type(const cylinder_t &cyl1, const cylinder_t &cyl2)
 {
-	return same_string(cyl1.type.description, cyl2.type.description) &&
-	       cyl1.cylinder_use == cyl2.cylinder_use;
+	return std::tie(cyl1.cylinder_use, cyl1.type.description) ==
+	       std::tie(cyl2.cylinder_use, cyl2.type.description);
 }
 
 static bool same_cylinder_size(const cylinder_t &cyl1, const cylinder_t &cyl2)
 {
-	return cyl1.type.size.mliter == cyl2.type.size.mliter &&
-	       cyl1.type.workingpressure.mbar == cyl2.type.workingpressure.mbar;
+	return std::tie(cyl1.type.size.mliter, cyl1.type.workingpressure.mbar) ==
+	       std::tie(cyl2.type.size.mliter, cyl2.type.workingpressure.mbar);
 }
 
 // Flags for comparing cylinders
@@ -1177,7 +1172,7 @@ EditCylinderBase::EditCylinderBase(int index, bool currentDiveOnly, bool nonProt
 	EditDivesBase(currentDiveOnly)
 {
 	// Get the old cylinder, bail if index is invalid
-	if (!current || index < 0 || index >= current->cylinders.nr) {
+	if (!current || index < 0 || index >= static_cast<int>(current->cylinders.size())) {
 		dives.clear();
 		return;
 	}
@@ -1189,12 +1184,12 @@ EditCylinderBase::EditCylinderBase(int index, bool currentDiveOnly, bool nonProt
 	cyl.reserve(dives.size());
 
 	for (dive *d: dives) {
-		if (index >= d->cylinders.nr)
+		if (index >= static_cast<int>(d->cylinders.size()))
 			continue;
 		if (nonProtectedOnly && is_cylinder_prot(d, index))
 			continue;
 		// We checked that the cylinder exists above.
-		const cylinder_t &cylinder = *get_cylinder(d, index);
+		const cylinder_t &cylinder = d->cylinders[index];
 		if (d != current &&
 		    (!same_cylinder_size(orig, cylinder) || !same_cylinder_type(orig, cylinder))) {
 			// when editing cylinders, we assume that the user wanted to edit the 'n-th' cylinder
@@ -1206,15 +1201,13 @@ EditCylinderBase::EditCylinderBase(int index, bool currentDiveOnly, bool nonProt
 		// that's silly as it's always the same value - but we need this vector of indices in the case where we add
 		// a cylinder to several dives as the spot will potentially be different in different dives
 		indexes.push_back(index);
-		cyl.push_back(clone_cylinder(cylinder));
+		cyl.push_back(cylinder);
 	}
 	dives = std::move(divesNew);
 }
 
 EditCylinderBase::~EditCylinderBase()
 {
-	for (cylinder_t c: cyl)
-		free_cylinder(c);
 }
 
 bool EditCylinderBase::workToBeDone()
@@ -1235,8 +1228,8 @@ RemoveCylinder::RemoveCylinder(int index, bool currentDiveOnly) :
 void RemoveCylinder::undo()
 {
 	for (size_t i = 0; i < dives.size(); ++i) {
-		std::vector<int> mapping = get_cylinder_map_for_add(dives[i]->cylinders.nr, indexes[i]);
-		add_cylinder(&dives[i]->cylinders, indexes[i], clone_cylinder(cyl[i]));
+		std::vector<int> mapping = get_cylinder_map_for_add(dives[i]->cylinders.size(), indexes[i]);
+		add_cylinder(&dives[i]->cylinders, indexes[i], cyl[i]);
 		cylinder_renumber(dives[i], &mapping[0]);
 		update_cylinder_related_info(dives[i]);
 		emit diveListNotifier.cylinderAdded(dives[i], indexes[i]);
@@ -1247,7 +1240,7 @@ void RemoveCylinder::undo()
 void RemoveCylinder::redo()
 {
 	for (size_t i = 0; i < dives.size(); ++i) {
-		std::vector<int> mapping = get_cylinder_map_for_remove(dives[i]->cylinders.nr, indexes[i]);
+		std::vector<int> mapping = get_cylinder_map_for_remove(dives[i]->cylinders.size(), indexes[i]);
 		remove_cylinder(dives[i], indexes[i]);
 		cylinder_renumber(dives[i], &mapping[0]);
 		update_cylinder_related_info(dives[i]);
@@ -1282,15 +1275,12 @@ EditCylinder::EditCylinder(int index, cylinder_t cylIn, EditCylinderType typeIn,
 	else
 		setText(Command::Base::tr("Edit cylinder (%n dive(s))", "", dives.size()));
 
-	QString description = cylIn.type.description;
-
 	// The base class copied the cylinders for us, let's edit them
 	for (int i = 0; i < (int)indexes.size(); ++i) {
 		switch (type) {
 		case EditCylinderType::TYPE:
-			free((void *)cyl[i].type.description);
 			cyl[i].type = cylIn.type;
-			cyl[i].type.description = copy_qstring(description);
+			cyl[i].type.description = cylIn.type.description;
 			cyl[i].cylinder_use = cylIn.cylinder_use;
 			break;
 		case EditCylinderType::PRESSURE:
@@ -1301,7 +1291,7 @@ EditCylinder::EditCylinder(int index, cylinder_t cylIn, EditCylinderType typeIn,
 			cyl[i].gasmix = cylIn.gasmix;
 			cyl[i].bestmix_o2 = cylIn.bestmix_o2;
 			cyl[i].bestmix_he = cylIn.bestmix_he;
-			sanitize_gasmix(&cyl[i].gasmix);
+			sanitize_gasmix(cyl[i].gasmix);
 			break;
 		}
 	}
@@ -1310,7 +1300,7 @@ EditCylinder::EditCylinder(int index, cylinder_t cylIn, EditCylinderType typeIn,
 void EditCylinder::redo()
 {
 	for (size_t i = 0; i < dives.size(); ++i) {
-		std::string name = cyl[i].type.description;
+		const std::string &name = cyl[i].type.description;
 		set_tank_info_data(tank_info_table, name, cyl[i].type.size, cyl[i].type.workingpressure);
 		std::swap(*get_cylinder(dives[i], indexes[i]), cyl[i]);
 		update_cylinder_related_info(dives[i]);
diff --git a/core/cochran.cpp b/core/cochran.cpp
index d39d73ef7..5cad4cd0b 100644
--- a/core/cochran.cpp
+++ b/core/cochran.cpp
@@ -672,24 +672,22 @@ static void cochran_parse_dive(const unsigned char *decode, unsigned mod,
 	case TYPE_GEMINI:
 	case TYPE_COMMANDER:
 		if (config.type == TYPE_GEMINI) {
-			cylinder_t cyl;
 			dc->model = "Gemini";
 			dc->deviceid = buf[0x18c] * 256 + buf[0x18d];	// serial no
-			fill_default_cylinder(dive.get(), &cyl);
+			cylinder_t cyl = default_cylinder(dive.get());
 			cyl.gasmix.o2.permille = (log[CMD_O2_PERCENT] / 256
 				+ log[CMD_O2_PERCENT + 1]) * 10;
 			cyl.gasmix.he.permille = 0;
-			add_cylinder(&dive->cylinders, 0, cyl);
+			add_cylinder(&dive->cylinders, 0, std::move(cyl));
 		} else {
 			dc->model = "Commander";
 			dc->deviceid = array_uint32_le(buf + 0x31e);	// serial no
 			for (g = 0; g < 2; g++) {
-				cylinder_t cyl;
-				fill_default_cylinder(dive.get(), &cyl);
+				cylinder_t cyl = default_cylinder(dive.get());
 				cyl.gasmix.o2.permille = (log[CMD_O2_PERCENT + g * 2] / 256
 					+ log[CMD_O2_PERCENT + g * 2 + 1]) * 10;
 				cyl.gasmix.he.permille = 0;
-				add_cylinder(&dive->cylinders, g, cyl);
+				add_cylinder(&dive->cylinders, g, std::move(cyl));
 			}
 		}
 
@@ -727,15 +725,14 @@ static void cochran_parse_dive(const unsigned char *decode, unsigned mod,
 		dc->model = "EMC";
 		dc->deviceid = array_uint32_le(buf + 0x31e);	// serial no
 		for (g = 0; g < 4; g++) {
-			cylinder_t cyl;
-			fill_default_cylinder(dive.get(), &cyl);
+			cylinder_t cyl = default_cylinder(dive.get());
 			cyl.gasmix.o2.permille =
 				(log[EMC_O2_PERCENT + g * 2] / 256
 				+ log[EMC_O2_PERCENT + g * 2 + 1]) * 10;
 			cyl.gasmix.he.permille =
 				(log[EMC_HE_PERCENT + g * 2] / 256
 				+ log[EMC_HE_PERCENT + g * 2 + 1]) * 10;
-			add_cylinder(&dive->cylinders, g, cyl);
+			add_cylinder(&dive->cylinders, g, std::move(cyl));
 		}
 
 		tm.tm_year = log[EMC_YEAR];
diff --git a/core/datatrak.cpp b/core/datatrak.cpp
index 2e4b59b8b..43da325a1 100644
--- a/core/datatrak.cpp
+++ b/core/datatrak.cpp
@@ -334,14 +334,13 @@ static char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive, struct
 	read_bytes(2);
 	if (tmp_2bytes != 0x7FFF) {
 		cylinder_t cyl;
-		std::string desc = cyl_type_by_size(tmp_2bytes * 10);
 		cyl.type.size.mliter = tmp_2bytes * 10;
-		cyl.type.description = desc.c_str();
+		cyl.type.description = cyl_type_by_size(tmp_2bytes * 10);
 		cyl.start.mbar = 200000;
 		cyl.gasmix.he.permille = 0;
 		cyl.gasmix.o2.permille = 210;
 		cyl.manually_added = true;
-		add_cloned_cylinder(&dt_dive->cylinders, cyl);
+		dt_dive->cylinders.push_back(std::move(cyl));
 	}
 
 	/*
@@ -372,7 +371,7 @@ static char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive, struct
 	 * Air used in bar*100.
 	 */
 	read_bytes(2);
-	if (tmp_2bytes != 0x7FFF && dt_dive->cylinders.nr > 0)
+	if (tmp_2bytes != 0x7FFF && dt_dive->cylinders.size() > 0)
 		get_cylinder(dt_dive, 0)->gas_used.mliter = lrint(get_cylinder(dt_dive, 0)->type.size.mliter * (tmp_2bytes / 100.0));
 
 	/*
@@ -548,10 +547,10 @@ static char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive, struct
 			free(compl_buffer);
 			goto bail;
 		}
-		if (is_nitrox && dt_dive->cylinders.nr > 0)
+		if (is_nitrox && dt_dive->cylinders.size() > 0)
 			get_cylinder(dt_dive, 0)->gasmix.o2.permille =
 					lrint(membuf[23] & 0x0F ? 20.0 + 2 * (membuf[23] & 0x0F) : 21.0) * 10;
-		if (is_O2 && dt_dive->cylinders.nr > 0)
+		if (is_O2 && dt_dive->cylinders.size() > 0)
 			get_cylinder(dt_dive, 0)->gasmix.o2.permille = membuf[23] * 10;
 		free(compl_buffer);
 	}
@@ -564,7 +563,7 @@ static char *dt_dive_parser(unsigned char *runner, struct dive *dt_dive, struct
 		dt_dive->dcs[0].deviceid = 0;
 	else
 		dt_dive->dcs[0].deviceid = 0xffffffff;
-	if (!is_SCR && dt_dive->cylinders.nr > 0) {
+	if (!is_SCR && dt_dive->cylinders.size() > 0) {
 		get_cylinder(dt_dive, 0)->end.mbar = get_cylinder(dt_dive, 0)->start.mbar -
 			((get_cylinder(dt_dive, 0)->gas_used.mliter / get_cylinder(dt_dive, 0)->type.size.mliter) * 1000);
 	}
diff --git a/core/dive.cpp b/core/dive.cpp
index a60657951..20687e392 100644
--- a/core/dive.cpp
+++ b/core/dive.cpp
@@ -17,6 +17,7 @@
 #include "errorhelper.h"
 #include "event.h"
 #include "extradata.h"
+#include "format.h"
 #include "interpolate.h"
 #include "qthelper.h"
 #include "membuffer.h"
@@ -121,8 +122,8 @@ void add_gas_switch_event(struct dive *dive, struct divecomputer *dc, int second
 	/* sanity check so we don't crash */
 	/* 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. */
-	//if (idx < 0 || idx >= dive->cylinders.nr) {
-	if (idx < 0 || idx >= dive->cylinders.nr + 1 || idx >= dive->cylinders.allocated) {
+	//if (idx < 0 || idx >= dive->cylinders.size()) {
+	if (idx < 0 || static_cast<size_t>(idx) >= dive->cylinders.size() + 1) {
 		report_error("Unknown cylinder index: %d", idx);
 		return;
 	}
@@ -135,9 +136,7 @@ struct gasmix get_gasmix_from_event(const struct dive *dive, const struct event
 	if (ev.is_gaschange()) {
 		int index = ev.gas.index;
 		// FIXME: The planner uses one past cylinder-count to signify "surface air". Remove in due course.
-		if (index == dive->cylinders.nr)
-			return gasmix_air;
-		if (index >= 0 && index < dive->cylinders.nr)
+		if (index >= 0 && static_cast<size_t>(index) < dive->cylinders.size() + 1)
 			return get_cylinder(dive, index)->gasmix;
 		return ev.gas.mix;
 	}
@@ -176,8 +175,7 @@ static void free_dive_structures(struct dive *d)
 	free(d->suit);
 	/* free tags, additional dive computers, and pictures */
 	taglist_free(d->tag_list);
-	clear_cylinder_table(&d->cylinders);
-	free(d->cylinders.cylinders);
+	d->cylinders.clear();
 	clear_weightsystem_table(&d->weightsystems);
 	free(d->weightsystems.weightsystems);
 	clear_picture_table(&d->pictures);
@@ -185,7 +183,7 @@ static void free_dive_structures(struct dive *d)
 }
 
 /* copy_dive makes duplicates of many components of a dive;
- * in order not to leak memory, we need to free those .
+ * 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 */
 void clear_dive(struct dive *d)
@@ -206,7 +204,6 @@ void copy_dive(const struct dive *s, struct dive *d)
 	 * relevant components that are referenced through pointers,
 	 * so all the strings and the structured lists */
 	*d = *s;
-	memset(&d->cylinders, 0, sizeof(d->cylinders));
 	memset(&d->weightsystems, 0, sizeof(d->weightsystems));
 	memset(&d->pictures, 0, sizeof(d->pictures));
 	d->full_text = NULL;
@@ -215,7 +212,6 @@ void copy_dive(const struct dive *s, struct dive *d)
 	d->diveguide = copy_string(s->diveguide);
 	d->notes = copy_string(s->notes);
 	d->suit = copy_string(s->suit);
-	copy_cylinders(&s->cylinders, &d->cylinders);
 	copy_weights(&s->weightsystems, &d->weightsystems);
 	copy_pictures(&s->pictures, &d->pictures);
 	d->tag_list = taglist_copy(s->tag_list);
@@ -293,11 +289,6 @@ void copy_events_until(const struct dive *sd, struct dive *dd, int dcNr, int tim
 	}
 }
 
-int nr_cylinders(const struct dive *dive)
-{
-	return dive->cylinders.nr;
-}
-
 int nr_weightsystems(const struct dive *dive)
 {
 	return dive->weightsystems.nr;
@@ -305,14 +296,13 @@ int nr_weightsystems(const struct dive *dive)
 
 void copy_used_cylinders(const struct dive *s, struct dive *d, bool used_only)
 {
-	int i;
 	if (!s || !d)
 		return;
 
-	clear_cylinder_table(&d->cylinders);
-	for (i = 0; i < s->cylinders.nr; i++) {
+	d->cylinders.clear();
+	for (auto [i, cyl]: enumerated_range(s->cylinders)) {
 		if (!used_only || is_cylinder_used(s, i) || get_cylinder(s, i)->cylinder_use == NOT_USED)
-			add_cloned_cylinder(&d->cylinders, *get_cylinder(s, i));
+			d->cylinders.push_back(cyl);
 	}
 }
 
@@ -354,12 +344,12 @@ static void update_temperature(temperature_t *temperature, int new_temp)
 
 /* Which cylinders had gas used? */
 #define SOME_GAS 5000
-static bool cylinder_used(const cylinder_t *cyl)
+static bool cylinder_used(const cylinder_t &cyl)
 {
 	int start_mbar, end_mbar;
 
-	start_mbar = cyl->start.mbar ?: cyl->sample_start.mbar;
-	end_mbar = cyl->end.mbar ?: cyl->sample_end.mbar;
+	start_mbar = cyl.start.mbar ?: cyl.sample_start.mbar;
+	end_mbar = cyl.end.mbar ?: cyl.sample_end.mbar;
 
 	// More than 5 bar used? This matches statistics.cpp
 	// heuristics
@@ -369,10 +359,10 @@ static bool cylinder_used(const cylinder_t *cyl)
 /* Get list of used cylinders. Returns the number of used cylinders. */
 static int get_cylinder_used(const struct dive *dive, bool used[])
 {
-	int i, num = 0;
+	int num = 0;
 
-	for (i = 0; i < dive->cylinders.nr; i++) {
-		used[i] = cylinder_used(get_cylinder(dive, i));
+	for (auto [i, cyl]: enumerated_range(dive->cylinders)) {
+		used[i] = cylinder_used(cyl);
 		if (used[i])
 			num++;
 	}
@@ -384,8 +374,8 @@ static bool has_unknown_used_cylinders(const struct dive *dive, const struct div
 				       const bool used_cylinders[], int num)
 {
 	int idx;
-	auto used_and_unknown = std::make_unique<bool[]>(dive->cylinders.nr);
-	std::copy(used_cylinders, used_cylinders + dive->cylinders.nr, used_and_unknown.get());
+	auto used_and_unknown = std::make_unique<bool[]>(dive->cylinders.size());
+	std::copy(used_cylinders, used_cylinders + dive->cylinders.size(), used_and_unknown.get());
 
 	/* We know about using the O2 cylinder in a CCR dive */
 	if (dc->divemode == CCR) {
@@ -419,16 +409,15 @@ static bool has_unknown_used_cylinders(const struct dive *dive, const struct div
 
 void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, int *mean, int *duration)
 {
-	int i;
 	int32_t lasttime = 0;
 	int lastdepth = 0;
 	int idx = 0;
 	int num_used_cylinders;
 
-	if (dive->cylinders.nr <= 0)
+	if (dive->cylinders.empty())
 		return;
 
-	for (i = 0; i < dive->cylinders.nr; i++)
+	for (size_t i = 0; i < dive->cylinders.size(); i++)
 		mean[i] = duration[i] = 0;
 	if (!dc)
 		return;
@@ -438,7 +427,7 @@ void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, i
 	 * if we don't actually know about the usage of all the
 	 * used cylinders.
 	 */
-	auto used_cylinders = std::make_unique<bool[]>(dive->cylinders.nr);
+	auto used_cylinders = std::make_unique<bool[]>(dive->cylinders.size());
 	num_used_cylinders = get_cylinder_used(dive, used_cylinders.get());
 	if (has_unknown_used_cylinders(dive, dc, used_cylinders.get(), num_used_cylinders)) {
 		/*
@@ -453,7 +442,7 @@ void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, i
 		 * For a single cylinder, use the overall mean
 		 * and duration
 		 */
-		for (i = 0; i < dive->cylinders.nr; i++) {
+		for (size_t i = 0; i < dive->cylinders.size(); i++) {
 			if (used_cylinders[i]) {
 				mean[i] = dc->meandepth.mm;
 				duration[i] = dc->duration.seconds;
@@ -466,7 +455,7 @@ void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, i
 		fake_dc(dc);
 	event_loop loop("gaschange");
 	const struct event *ev = loop.next(*dc);
-	std::vector<int> depthtime(dive->cylinders.nr, 0);
+	std::vector<int> depthtime(dive->cylinders.size(), 0);
 	for (auto it = dc->samples.begin(); it != dc->samples.end(); ++it) {
 		int32_t time = it->time.seconds;
 		int depth = it->depth.mm;
@@ -494,7 +483,7 @@ void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, i
 		lastdepth = depth;
 		lasttime = time;
 	}
-	for (i = 0; i < dive->cylinders.nr; i++) {
+	for (size_t i = 0; i < dive->cylinders.size(); i++) {
 		if (duration[i])
 			mean[i] = (depthtime[i] + duration[i] / 2) / duration[i];
 	}
@@ -529,7 +518,7 @@ static int same_rounded_pressure(pressure_t a, pressure_t b)
 int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *dc)
 {
 	int res = 0;
-	if (!dive->cylinders.nr)
+	if (dive->cylinders.empty())
 		return -1;
 	if (dc) {
 		const struct event *ev = get_first_event(*dc, "gaschange");
@@ -538,7 +527,7 @@ int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *
 		else if (dc->divemode == CCR)
 			res = std::max(get_cylinder_idx_by_use(dive, DILUENT), res);
 	}
-	return res < dive->cylinders.nr ? res : 0;
+	return static_cast<size_t>(res) < dive->cylinders.size() ? res : 0;
 }
 
 /* this gets called when the dive mode has changed (so OC vs. CC)
@@ -598,22 +587,18 @@ void update_setpoint_events(const struct dive *dive, struct divecomputer *dc)
  * cylinder name is independent from the gasmix, and different
  * gasmixes have different compressibility.
  */
-static void match_standard_cylinder(cylinder_type_t *type)
+static void match_standard_cylinder(cylinder_type_t &type)
 {
-	double cuft, bar;
-	int psi, len;
-	const char *fmt;
-	char buffer[40], *p;
-
 	/* Do we already have a cylinder description? */
-	if (type->description)
+	if (!type.description.empty())
 		return;
 
-	bar = type->workingpressure.mbar / 1000.0;
-	cuft = ml_to_cuft(type->size.mliter);
+	double bar = type.workingpressure.mbar / 1000.0;
+	double cuft = ml_to_cuft(type.size.mliter);
 	cuft *= bar_to_atm(bar);
-	psi = lrint(to_PSI(type->workingpressure));
+	int psi = lrint(to_PSI(type.workingpressure));
 
+	const char *fmt;
 	switch (psi) {
 	case 2300 ... 2500: /* 2400 psi: LP tank */
 		fmt = "LP%d";
@@ -633,12 +618,7 @@ static void match_standard_cylinder(cylinder_type_t *type)
 	default:
 		return;
 	}
-	len = snprintf(buffer, sizeof(buffer), fmt, (int)lrint(cuft));
-	p = (char *)malloc(len + 1);
-	if (!p)
-		return;
-	memcpy(p, buffer, len + 1);
-	type->description = p;
+	type.description = format_string_std(fmt, (int)lrint(cuft));
 }
 
 /*
@@ -651,14 +631,14 @@ static void match_standard_cylinder(cylinder_type_t *type)
  * We internally use physical size only. But we save the workingpressure
  * so that we can do the conversion if required.
  */
-static void sanitize_cylinder_type(cylinder_type_t *type)
+static void sanitize_cylinder_type(cylinder_type_t &type)
 {
 	/* If we have no working pressure, it had *better* be just a physical size! */
-	if (!type->workingpressure.mbar)
+	if (!type.workingpressure.mbar)
 		return;
 
 	/* No size either? Nothing to go on */
-	if (!type->size.mliter)
+	if (!type.size.mliter)
 		return;
 
 	/* Ok, we have both size and pressure: try to match a description */
@@ -667,11 +647,9 @@ static void sanitize_cylinder_type(cylinder_type_t *type)
 
 static void sanitize_cylinder_info(struct dive *dive)
 {
-	int i;
-
-	for (i = 0; i < dive->cylinders.nr; i++) {
-		sanitize_gasmix(&get_cylinder(dive, i)->gasmix);
-		sanitize_cylinder_type(&get_cylinder(dive, i)->type);
+	for (auto &cyl :dive->cylinders) {
+		sanitize_gasmix(cyl.gasmix);
+		sanitize_cylinder_type(cyl.type);
 	}
 }
 
@@ -935,19 +913,19 @@ static void simplify_dc_pressures(struct divecomputer &dc)
 /* Do we need a sensor -> cylinder mapping? */
 static void fixup_start_pressure(struct dive *dive, int idx, pressure_t p)
 {
-	if (idx >= 0 && idx < dive->cylinders.nr) {
-		cylinder_t *cyl = get_cylinder(dive, idx);
-		if (p.mbar && !cyl->sample_start.mbar)
-			cyl->sample_start = p;
+	if (idx >= 0 && static_cast<size_t>(idx) < dive->cylinders.size()) {
+		cylinder_t &cyl = dive->cylinders[idx];
+		if (p.mbar && !cyl.sample_start.mbar)
+			cyl.sample_start = p;
 	}
 }
 
 static void fixup_end_pressure(struct dive *dive, int idx, pressure_t p)
 {
-	if (idx >= 0 && idx < dive->cylinders.nr) {
-		cylinder_t *cyl = get_cylinder(dive, idx);
-		if (p.mbar && !cyl->sample_end.mbar)
-			cyl->sample_end = p;
+	if (idx >= 0 && static_cast<size_t>(idx) < dive->cylinders.size()) {
+		cylinder_t &cyl = dive->cylinders[idx];
+		if (p.mbar && !cyl.sample_end.mbar)
+			cyl.sample_end = p;
 	}
 }
 
@@ -1003,13 +981,13 @@ static bool validate_gaschange(struct dive *dive, struct event &event)
 	if (event.gas.index >= 0)
 		return true;
 
-	index = find_best_gasmix_match(event.gas.mix, &dive->cylinders);
-	if (index < 0 || index >= dive->cylinders.nr)
+	index = find_best_gasmix_match(event.gas.mix, dive->cylinders);
+	if (index < 0 || static_cast<size_t>(index) >= dive->cylinders.size())
 		return false;
 
 	/* Fix up the event to have the right information */
 	event.gas.index = index;
-	event.gas.mix = get_cylinder(dive, index)->gasmix;
+	event.gas.mix = dive->cylinders[index].gasmix;
 
 	/* Convert to odd libdivecomputer format */
 	o2 = get_o2(event.gas.mix);
@@ -1094,7 +1072,7 @@ static void fixup_dc_sample_sensors(struct dive *dive, struct divecomputer &dc)
 	}
 
 	// Ignore the sensors we have cylinders for
-	sensor_mask >>= dive->cylinders.nr;
+	sensor_mask >>= dive->cylinders.size();
 
 	// Do we need to add empty cylinders?
 	while (sensor_mask) {
@@ -1160,13 +1138,12 @@ struct dive *fixup_dive(struct dive *dive)
 	fixup_duration(dive);
 	fixup_watertemp(dive);
 	fixup_airtemp(dive);
-	for (i = 0; i < dive->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(dive, i);
-		add_cylinder_description(cyl->type);
-		if (same_rounded_pressure(cyl->sample_start, cyl->start))
-			cyl->start.mbar = 0;
-		if (same_rounded_pressure(cyl->sample_end, cyl->end))
-			cyl->end.mbar = 0;
+	for (auto &cyl: dive->cylinders) {
+		add_cylinder_description(cyl.type);
+		if (same_rounded_pressure(cyl.sample_start, cyl.start))
+			cyl.start.mbar = 0;
+		if (same_rounded_pressure(cyl.sample_end, cyl.end))
+			cyl.end.mbar = 0;
 	}
 	update_cylinder_related_info(dive);
 	for (i = 0; i < dive->weightsystems.nr; i++) {
@@ -1487,12 +1464,9 @@ pick_b:
  *                  cylinder_use_type = an enum, one of {oxygen, diluent, bailout} */
 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++) {
-		if (get_cylinder(dive, cylinder_index)->cylinder_use == cylinder_use_type)
-			return cylinder_index; // return the index of the cylinder with that cylinder use type
-	}
-	return -1; // negative number means cylinder_use_type not found in list of cylinders
+	auto it = std::find_if(dive->cylinders.begin(), dive->cylinders.end(), [cylinder_use_type]
+			       (auto &cyl) { return cyl.cylinder_use == cylinder_use_type; });
+	return it != dive->cylinders.end() ? it - dive->cylinders.begin() : -1;
 }
 
 /* Force an initial gaschange event to the (old) gas #0 */
@@ -1580,13 +1554,13 @@ void cylinder_renumber(struct dive *dive, int mapping[])
 		dc_cylinder_renumber(dive, dc, mapping);
 }
 
-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++) {
+	struct gasmix mygas = cyl.gasmix;
+	for (auto [i, cyl]: enumerated_range(dive->cylinders)) {
 		if (i == cylid)
 			continue;
-		struct gasmix gas2 = get_cylinder(dive, i)->gasmix;
+		struct gasmix gas2 = cyl.gasmix;
 		if (gasmix_distance(mygas, gas2) == 0 && (is_cylinder_used(dive, i) || check_unused))
 			return i;
 	}
@@ -1614,20 +1588,15 @@ static int different_manual_pressures(const cylinder_t *a, const cylinder_t *b)
  */
 static int match_cylinder(const cylinder_t *cyl, const struct dive *dive, const bool try_match[])
 {
-	int i;
-
-	for (i = 0; i < dive->cylinders.nr; i++) {
-		const cylinder_t *target;
-
+	for (auto [i, target]: enumerated_range(dive->cylinders)) {
 		if (!try_match[i])
 			continue;
 
-		target = get_cylinder(dive, i);
-		if (!same_gasmix(cyl->gasmix, target->gasmix))
+		if (!same_gasmix(cyl->gasmix, target.gasmix))
 			continue;
-		if (cyl->cylinder_use != target->cylinder_use)
+		if (cyl->cylinder_use != target.cylinder_use)
 			continue;
-		if (different_manual_pressures(cyl, target))
+		if (different_manual_pressures(cyl, &target))
 			continue;
 
 		/* open question: Should we check sizes too? */
@@ -1679,8 +1648,8 @@ static void merge_one_cylinder(cylinder_t *a, const cylinder_t *b)
 		a->type.size.mliter = b->type.size.mliter;
 	if (!a->type.workingpressure.mbar)
 		a->type.workingpressure.mbar = b->type.workingpressure.mbar;
-	if (empty_string(a->type.description))
-		a->type.description = copy_string(b->type.description);
+	if (a->type.description.empty())
+		a->type.description = b->type.description;
 
 	/* If either cylinder has manually entered pressures, try to merge them.
 	 * Use pressures from divecomputer samples if only one cylinder has such a value.
@@ -1697,24 +1666,24 @@ static void merge_one_cylinder(cylinder_t *a, const cylinder_t *b)
 	a->bestmix_he = a->bestmix_he && b->bestmix_he;
 }
 
-static bool cylinder_has_data(const cylinder_t *cyl)
+static bool cylinder_has_data(const cylinder_t &cyl)
 {
-	return !cyl->type.size.mliter &&
-	       !cyl->type.workingpressure.mbar &&
-	       !cyl->type.description &&
-	       !cyl->gasmix.o2.permille &&
-	       !cyl->gasmix.he.permille &&
-	       !cyl->start.mbar &&
-	       !cyl->end.mbar &&
-	       !cyl->sample_start.mbar &&
-	       !cyl->sample_end.mbar &&
-	       !cyl->gas_used.mliter &&
-	       !cyl->deco_gas_used.mliter;
+	return !cyl.type.size.mliter &&
+	       !cyl.type.workingpressure.mbar &&
+	       cyl.type.description.empty() &&
+	       !cyl.gasmix.o2.permille &&
+	       !cyl.gasmix.he.permille &&
+	       !cyl.start.mbar &&
+	       !cyl.end.mbar &&
+	       !cyl.sample_start.mbar &&
+	       !cyl.sample_end.mbar &&
+	       !cyl.gas_used.mliter &&
+	       !cyl.deco_gas_used.mliter;
 }
 
 static bool cylinder_in_use(const struct dive *dive, int idx)
 {
-	if (idx < 0 || idx >= dive->cylinders.nr)
+	if (idx < 0 || static_cast<size_t>(idx) >= dive->cylinders.size())
 		return false;
 
 	/* This tests for gaschange events or pressure changes */
@@ -1722,7 +1691,7 @@ static bool cylinder_in_use(const struct dive *dive, int idx)
 		return true;
 
 	/* This tests for typenames or gas contents */
-	return cylinder_has_data(get_cylinder(dive, idx));
+	return cylinder_has_data(dive->cylinders[idx]);
 }
 
 /*
@@ -1738,22 +1707,21 @@ static bool cylinder_in_use(const struct dive *dive, int idx)
 static void merge_cylinders(struct dive *res, const struct dive *a, const struct dive *b,
 			    int mapping_a[], int mapping_b[])
 {
-	int i;
-	int max_cylinders = a->cylinders.nr + b->cylinders.nr;
+	size_t max_cylinders = a->cylinders.size() + b->cylinders.size();
 	auto used_in_a = std::make_unique<bool[]>(max_cylinders);
 	auto used_in_b = std::make_unique<bool[]>(max_cylinders);
 	auto try_to_match = std::make_unique<bool[]>(max_cylinders);
 	std::fill(try_to_match.get(), try_to_match.get() + max_cylinders, false);
 
 	/* First, clear all cylinders in destination */
-	clear_cylinder_table(&res->cylinders);
+	res->cylinders.clear();
 
 	/* Clear all cylinder mappings */
-	std::fill(mapping_a, mapping_a + a->cylinders.nr, -1);
-	std::fill(mapping_b, mapping_b + b->cylinders.nr, -1);
+	std::fill(mapping_a, mapping_a + a->cylinders.size(), -1);
+	std::fill(mapping_b, mapping_b + b->cylinders.size(), -1);
 
 	/* Calculate usage map of cylinders, clear matching map */
-	for (i = 0; i < max_cylinders; i++) {
+	for (size_t i = 0; i < max_cylinders; i++) {
 		used_in_a[i] = cylinder_in_use(a, i);
 		used_in_b[i] = cylinder_in_use(b, i);
 	}
@@ -1762,20 +1730,20 @@ static void merge_cylinders(struct dive *res, const struct dive *a, const struct
 	 * For each cylinder in 'a' that is used, copy it to 'res'.
 	 * These are also potential matches for 'b' to use.
 	 */
-	for (i = 0; i < max_cylinders; i++) {
-		int res_nr = res->cylinders.nr;
+	for (size_t i = 0; i < max_cylinders; i++) {
+		size_t res_nr = res->cylinders.size();
 		if (!used_in_a[i])
 			continue;
-		mapping_a[i] = res_nr;
+		mapping_a[i] = static_cast<int>(res_nr);
 		try_to_match[res_nr] = true;
-		add_cloned_cylinder(&res->cylinders, *get_cylinder(a, i));
+		res->cylinders.push_back(a->cylinders[i]);
 	}
 
 	/*
 	 * For each cylinder in 'b' that is used, try to match it
 	 * with an existing cylinder in 'res' from 'a'
 	 */
-	for (i = 0; i < b->cylinders.nr; i++) {
+	for (size_t i = 0; i < b->cylinders.size(); i++) {
 		int j;
 
 		if (!used_in_b[i])
@@ -1785,9 +1753,9 @@ static void merge_cylinders(struct dive *res, const struct dive *a, const struct
 
 		/* No match? Add it to the result */
 		if (j < 0) {
-			int res_nr = res->cylinders.nr;
-			mapping_b[i] = res_nr;
-			add_cloned_cylinder(&res->cylinders, *get_cylinder(b, i));
+			size_t res_nr = res->cylinders.size();
+			mapping_b[i] = static_cast<int>(res_nr);
+			res->cylinders.push_back(b->cylinders[i]);
 			continue;
 		}
 
@@ -2402,8 +2370,8 @@ struct dive *merge_dives(const struct dive *a, const struct dive *b, int offset,
 	taglist_merge(&res->tag_list, a->tag_list, b->tag_list);
 	/* if we get dives without any gas / cylinder information in an import, make sure
 	 * that there is at leatst one entry in the cylinder map for that dive */
-	auto cylinders_map_a = std::make_unique<int[]>(std::max(1, a->cylinders.nr));
-	auto cylinders_map_b = std::make_unique<int[]>(std::max(1, b->cylinders.nr));
+	auto cylinders_map_a = std::make_unique<int[]>(std::max(size_t(1), a->cylinders.size()));
+	auto cylinders_map_b = std::make_unique<int[]>(std::max(size_t(1), b->cylinders.size()));
 	merge_cylinders(res, a, b, cylinders_map_a.get(), cylinders_map_b.get());
 	merge_equipment(res, a, b);
 	merge_temperatures(res, a, b);
@@ -2456,7 +2424,7 @@ static void force_fixup_dive(struct dive *d)
 	int old_mintemp = d->mintemp.mkelvin;
 	int old_maxtemp = d->maxtemp.mkelvin;
 	duration_t old_duration = d->duration;
-	std::vector<start_end_pressure> old_pressures(d->cylinders.nr);
+	std::vector<start_end_pressure> old_pressures(d->cylinders.size());
 
 	d->maxdepth.mm = 0;
 	dc->maxdepth.mm = 0;
@@ -2465,12 +2433,11 @@ static void force_fixup_dive(struct dive *d)
 	d->duration.seconds = 0;
 	d->maxtemp.mkelvin = 0;
 	d->mintemp.mkelvin = 0;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(d, i);
-		old_pressures[i].start = cyl->start;
-		old_pressures[i].end = cyl->end;
-		cyl->start.mbar = 0;
-		cyl->end.mbar = 0;
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
+		old_pressures[i].start = cyl.start;
+		old_pressures[i].end = cyl.end;
+		cyl.start.mbar = 0;
+		cyl.end.mbar = 0;
 	}
 
 	fixup_dive(d);
@@ -2489,11 +2456,11 @@ static void force_fixup_dive(struct dive *d)
 
 	if (!d->duration.seconds)
 		d->duration = old_duration;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		if (!get_cylinder(d, i)->start.mbar)
-			get_cylinder(d, i)->start = old_pressures[i].start;
-		if (!get_cylinder(d, i)->end.mbar)
-			get_cylinder(d, i)->end = old_pressures[i].end;
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
+		if (!cyl.start.mbar)
+			cyl.start = old_pressures[i].start;
+		if (!cyl.end.mbar)
+			cyl.end = old_pressures[i].end;
 	}
 }
 
@@ -3171,7 +3138,7 @@ gasmix_loop::gasmix_loop(const struct dive &d, const struct divecomputer &dc) :
 	dive(d), dc(dc), last(gasmix_air), loop("gaschange")
 {
 	/* if there is no cylinder, return air */
-	if (dive.cylinders.nr <= 0)
+	if (dive.cylinders.empty())
 		return;
 
 	/* on first invocation, get initial gas mix and first event (if any) */
@@ -3183,7 +3150,7 @@ gasmix_loop::gasmix_loop(const struct dive &d, const struct divecomputer &dc) :
 gasmix gasmix_loop::next(int time)
 {
 	/* if there is no cylinder, return air */
-	if (dive.cylinders.nr <= 0)
+	if (dive.cylinders.empty())
 		return last;
 
 	while (ev && ev->time.seconds <= time) {
diff --git a/core/dive.h b/core/dive.h
index 2e3747856..811b25ff6 100644
--- a/core/dive.h
+++ b/core/dive.h
@@ -30,7 +30,7 @@ struct dive {
 	struct dive_site *dive_site = nullptr;
 	char *notes = nullptr;
 	char *diveguide = nullptr, *buddy = nullptr;
-	struct cylinder_table cylinders = { };
+	struct cylinder_table cylinders;
 	struct weightsystem_table weightsystems = { };
 	char *suit = nullptr;
 	int number = 0;
@@ -74,7 +74,7 @@ extern bool dive_cache_is_valid(const struct dive *dive);
 
 extern int get_cylinder_idx_by_use(const struct dive *dive, enum cylinderuse cylinder_use_type);
 extern void cylinder_renumber(struct dive *dive, int mapping[]);
-extern int same_gasmix_cylinder(const cylinder_t *cyl, int cylid, const struct dive *dive, bool check_unused);
+extern int same_gasmix_cylinder(const cylinder_t &cyl, int cylid, const struct dive *dive, bool check_unused);
 
 /* when selectively copying dive information, which parts should be copied? */
 struct dive_components {
@@ -190,7 +190,6 @@ extern struct event create_gas_switch_event(struct dive *dive, struct divecomput
 extern void per_cylinder_mean_depth(const struct dive *dive, struct divecomputer *dc, int *mean, int *duration);
 extern int get_cylinder_index(const struct dive *dive, const struct event &ev);
 extern struct gasmix get_gasmix_from_event(const struct dive *, const struct event &ev);
-extern int nr_cylinders(const struct dive *dive);
 extern int nr_weightsystems(const struct dive *dive);
 extern bool cylinder_with_sensor_sample(const struct dive *dive, int cylinder_id);
 
diff --git a/core/divelist.cpp b/core/divelist.cpp
index 53dcf2d46..348cb091d 100644
--- a/core/divelist.cpp
+++ b/core/divelist.cpp
@@ -32,19 +32,17 @@
  */
 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;
 
-	for (i = 0; i < dive->cylinders.nr; i++) {
-		const cylinder_t *cyl = get_cylinder(dive, i);
-		int o2 = get_o2(cyl->gasmix);
-		int he = get_he(cyl->gasmix);
+	for (auto [i, cyl]: enumerated_range(dive->cylinders)) {
+		int o2 = get_o2(cyl.gasmix);
+		int he = get_he(cyl.gasmix);
 
 		if (!is_cylinder_used(dive, i))
 			continue;
-		if (cyl->cylinder_use == OXYGEN)
+		if (cyl.cylinder_use == OXYGEN)
 			continue;
-		if (cyl->cylinder_use == NOT_USED)
+		if (cyl.cylinder_use == NOT_USED)
 			continue;
 		if (o2 > maxo2)
 			maxo2 = o2;
@@ -337,12 +335,11 @@ static double calculate_airuse(const struct dive *dive)
 	if (dive->dcs[0].divemode == CCR)
 		return 0.0;
 
-	for (int i = 0; i < dive->cylinders.nr; i++) {
+	for (auto [i, cyl]: enumerated_range(dive->cylinders)) {
 		pressure_t start, end;
-		const cylinder_t *cyl = get_cylinder(dive, i);
 
-		start = cyl->start.mbar ? cyl->start : cyl->sample_start;
-		end = cyl->end.mbar ? cyl->end : cyl->sample_end;
+		start = cyl.start.mbar ? cyl.start : cyl.sample_start;
+		end = cyl.end.mbar ? cyl.end : cyl.sample_end;
 		if (!end.mbar || start.mbar <= end.mbar) {
 			// If a cylinder is used but we do not have info on amout of gas used
 			// better not pretend we know the total gas use.
@@ -354,7 +351,7 @@ static double calculate_airuse(const struct dive *dive)
 				continue;
 		}
 
-		airuse += gas_volume(cyl, start) - gas_volume(cyl, end);
+		airuse += gas_volume(&cyl, start) - gas_volume(&cyl, end);
 	}
 	return airuse / 1000.0;
 }
diff --git a/core/equipment.cpp b/core/equipment.cpp
index bce1c4eed..81c919640 100644
--- a/core/equipment.cpp
+++ b/core/equipment.cpp
@@ -18,9 +18,43 @@
 #include "divelog.h"
 #include "errorhelper.h"
 #include "pref.h"
+#include "range.h"
 #include "subsurface-string.h"
 #include "table.h"
 
+cylinder_t::cylinder_t() = default;
+cylinder_t::~cylinder_t() = default;
+
+static cylinder_t make_surface_air_cylinder()
+{
+	cylinder_t res;
+	res.cylinder_use = NOT_USED;
+	return res;
+}
+static const cylinder_t surface_air_cylinder = make_surface_air_cylinder();
+
+static void warn_index(size_t i, size_t max)
+{
+	if (i >= max + 1) {
+		report_info("Warning: accessing invalid cylinder %lu (%lu existing)",
+			static_cast<unsigned long>(i), static_cast<unsigned long>(max));
+	}
+}
+
+cylinder_t &cylinder_table::operator[](size_t i)
+{
+	warn_index(i, size());
+	return i < size() ? std::vector<cylinder_t>::operator[](i)
+			  : const_cast<cylinder_t &>(surface_air_cylinder);
+}
+
+const cylinder_t &cylinder_table::operator[](size_t i) const
+{
+	warn_index(i, size());
+	return i < size() ? std::vector<cylinder_t>::operator[](i)
+			  : surface_air_cylinder;
+}
+
 /* Warning: this has strange semantics for C-code! Not the weightsystem object
  * 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.
@@ -31,12 +65,6 @@ void free_weightsystem(weightsystem_t ws)
 	ws.description = NULL;
 }
 
-void free_cylinder(cylinder_t c)
-{
-	free((void *)c.type.description);
-	c.type.description = NULL;
-}
-
 void copy_weights(const struct weightsystem_table *s, struct weightsystem_table *d)
 {
 	clear_weightsystem_table(d);
@@ -44,14 +72,6 @@ void copy_weights(const struct weightsystem_table *s, struct weightsystem_table
 		add_cloned_weightsystem(d, s->weightsystems[i]);
 }
 
-void copy_cylinders(const struct cylinder_table *s, struct cylinder_table *d)
-{
-	int i;
-	clear_cylinder_table(d);
-	for (i = 0; i < s->nr; i++)
-		add_cloned_cylinder(d, s->cylinders[i]);
-}
-
 /* weightsystem table functions */
 //static MAKE_GET_IDX(weightsystem_table, weightsystem_t, weightsystems)
 static MAKE_GROW_TABLE(weightsystem_table, weightsystem_t, weightsystems)
@@ -62,16 +82,6 @@ static MAKE_REMOVE_FROM(weightsystem_table, weightsystems)
 //MAKE_REMOVE(weightsystem_table, weightsystem_t, weightsystem)
 MAKE_CLEAR_TABLE(weightsystem_table, weightsystems, weightsystem)
 
-/* cylinder table functions */
-//static MAKE_GET_IDX(cylinder_table, cylinder_t, cylinders)
-static MAKE_GROW_TABLE(cylinder_table, cylinder_t, cylinders)
-//static MAKE_GET_INSERTION_INDEX(cylinder_table, cylinder_t, cylinders, cylinder_less_than)
-static MAKE_ADD_TO(cylinder_table, cylinder_t, cylinders)
-static MAKE_REMOVE_FROM(cylinder_table, cylinders)
-//MAKE_SORT(cylinder_table, cylinder_t, cylinders, comp_cylinders)
-//MAKE_REMOVE(cylinder_table, cylinder_t, cylinder)
-MAKE_CLEAR_TABLE(cylinder_table, cylinders, cylinder)
-
 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")
 };
@@ -144,11 +154,11 @@ std::pair<volume_t, pressure_t> get_tank_info_data(const std::vector<tank_info>
 
 void add_cylinder_description(const cylinder_type_t &type)
 {
-	std::string desc = type.description ? type.description : std::string();
+	const std::string &desc = type.description;
 	if (desc.empty())
 		return;
 	if (std::any_of(tank_info_table.begin(), tank_info_table.end(),
-			[&type](const tank_info &info) { return info.name == type.description; }))
+			[&desc](const tank_info &info) { return info.name == desc; }))
 		return;
 	add_tank_info_metric(tank_info_table, desc, type.size.mliter,
 			     type.workingpressure.mbar / 1000);
@@ -191,30 +201,16 @@ void add_cloned_weightsystem(struct weightsystem_table *t, weightsystem_t ws)
 	add_to_weightsystem_table(t, t->nr, clone_weightsystem(ws));
 }
 
-cylinder_t clone_cylinder(cylinder_t cyl)
+/* Add a clone of a weightsystem to the end of a weightsystem table.
+ * Cloned means that the description-string is copied. */
+void add_cloned_weightsystem_at(struct weightsystem_table *t, weightsystem_t ws)
 {
-	cylinder_t res = cyl;
-	res.type.description = copy_string(res.type.description);
-	return res;
+	add_to_weightsystem_table(t, t->nr, clone_weightsystem(ws));
 }
 
 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
-	 * every single cylinder table there is an empty cylinder that can
-	 * be used by the planner as "surface air" cylinder. Fix this.
-	 */
-	add_to_cylinder_table(t, t->nr, cylinder_t());
-	t->nr--;
-	t->cylinders[t->nr].cylinder_use = NOT_USED;
-}
-
-/* Add a clone of a cylinder to the end of a cylinder table.
- * Cloned means that the description-string is copied. */
-void add_cloned_cylinder(struct cylinder_table *t, cylinder_t cyl)
-{
-	add_cylinder(t, t->nr, clone_cylinder(cyl));
+	t->insert(t->begin() + idx, std::move(cyl));
 }
 
 bool same_weightsystem(weightsystem_t w1, weightsystem_t w2)
@@ -250,17 +246,12 @@ int gas_volume(const cylinder_t *cyl, pressure_t p)
 	return lrint(cyl->type.size.mliter * bar_to_atm(bar) / z_factor);
 }
 
-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;
 
-	for (i = 0; i < cylinders->nr; i++) {
-		const cylinder_t *match;
-		int distance;
-
-		match = cylinders->cylinders + i;
-		distance = gasmix_distance(mix, match->gasmix);
+	for (auto [i, match]: enumerated_range(cylinders)) {
+		int distance = gasmix_distance(mix, match.gasmix);
 		if (distance >= score)
 			continue;
 		best = i;
@@ -336,10 +327,8 @@ void reset_tank_info_table(std::vector<tank_info> &table)
 	/* Add cylinders from dive list */
 	for (int i = 0; i < divelog.dives->nr; ++i) {
 		const struct dive *dive = divelog.dives->dives[i];
-		for (int j = 0; j < dive->cylinders.nr; j++) {
-			const cylinder_t *cyl = get_cylinder(dive, j);
-			add_cylinder_description(cyl->type);
-		}
+		for (auto &cyl: dive->cylinders)
+			add_cylinder_description(cyl.type);
 	}
 }
 
@@ -357,7 +346,7 @@ struct std::vector<ws_info> ws_info_table = {
 
 void remove_cylinder(struct dive *dive, int idx)
 {
-	remove_from_cylinder_table(&dive->cylinders, idx);
+	dive->cylinders.erase(dive->cylinders.begin() + idx);
 }
 
 void remove_weightsystem(struct dive *dive, int idx)
@@ -380,68 +369,61 @@ void reset_cylinders(struct dive *dive, bool track_gas)
 {
 	pressure_t decopo2 = {.mbar = prefs.decopo2};
 
-	for (int i = 0; i < dive->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(dive, i);
-		if (cyl->depth.mm == 0) /* if the gas doesn't give a mod, calculate based on prefs */
-			cyl->depth = gas_mod(cyl->gasmix, decopo2, dive, M_OR_FT(3,10));
+	for (cylinder_t &cyl: dive->cylinders) {
+		if (cyl.depth.mm == 0) /* if the gas doesn't give a mod, calculate based on prefs */
+			cyl.depth = gas_mod(cyl.gasmix, decopo2, dive, M_OR_FT(3,10));
 		if (track_gas)
-			cyl->start.mbar = cyl->end.mbar = cyl->type.workingpressure.mbar;
-		cyl->gas_used.mliter = 0;
-		cyl->deco_gas_used.mliter = 0;
+			cyl.start.mbar = cyl.end.mbar = cyl.type.workingpressure.mbar;
+		cyl.gas_used.mliter = 0;
+		cyl.deco_gas_used.mliter = 0;
 	}
 }
 
-static void copy_cylinder_type(const cylinder_t *s, cylinder_t *d)
+static void copy_cylinder_type(const cylinder_t &s, cylinder_t &d)
 {
-	free_cylinder(*d);
-	d->type = s->type;
-	d->type.description = s->type.description ? strdup(s->type.description) : NULL;
-	d->gasmix = s->gasmix;
-	d->depth = s->depth;
-	d->cylinder_use = s->cylinder_use;
-	d->manually_added = true;
+	d.type = s.type;
+	d.gasmix = s.gasmix;
+	d.depth = s.depth;
+	d.cylinder_use = s.cylinder_use;
+	d.manually_added = true;
 }
 
 /* copy the equipment data part of the cylinders but keep pressures */
 void copy_cylinder_types(const struct dive *s, struct dive *d)
 {
-	int i;
 	if (!s || !d)
 		return;
 
-	for (i = 0; i < s->cylinders.nr && i < d->cylinders.nr; i++)
-		copy_cylinder_type(get_cylinder(s, i), get_cylinder(d, i));
+	for (size_t i = 0; i < s->cylinders.size() && i < d->cylinders.size(); i++)
+		copy_cylinder_type(s->cylinders[i], d->cylinders[i]);
 
-	for ( ; i < s->cylinders.nr; i++)
-		add_cloned_cylinder(&d->cylinders, *get_cylinder(s, i));
+	for (size_t i = d->cylinders.size(); i < s->cylinders.size(); i++)
+		d->cylinders.push_back(s->cylinders[i]);
 }
 
 cylinder_t *add_empty_cylinder(struct cylinder_table *t)
 {
-	cylinder_t cyl;
-	cyl.type.description = strdup("");
-	add_cylinder(t, t->nr, cyl);
-	return &t->cylinders[t->nr - 1];
+	t->emplace_back();
+	return &t->back();
 }
 
 /* access to cylinders is controlled by two functions:
  * - get_cylinder() returns the cylinder of a dive and supposes that
  *   the cylinder with the given index exists. If it doesn't, an error
- *   message is printed and NULL returned.
+ *   message is printed and the "surface air" cylinder returned.
+ *   (NOTE: this MUST not be written into!).
  * - get_or_create_cylinder() creates an empty cylinder if it doesn't exist.
  *   Multiple cylinders might be created if the index is bigger than the
  *   number of existing cylinders
  */
-cylinder_t *get_cylinder(const struct dive *d, int idx)
+cylinder_t *get_cylinder(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. */
-	// if (idx < 0 || idx >= d->cylinders.nr) {
-	if (idx < 0 || idx >= d->cylinders.nr + 1 || idx >= d->cylinders.allocated) {
-		report_info("Warning: accessing invalid cylinder %d (%d existing)", idx, d->cylinders.nr);
-		return NULL;
-	}
-	return &d->cylinders.cylinders[idx];
+	return &d->cylinders[idx];
+}
+
+const cylinder_t *get_cylinder(const struct dive *d, int idx)
+{
+	return &d->cylinders[idx];
 }
 
 cylinder_t *get_or_create_cylinder(struct dive *d, int idx)
@@ -450,9 +432,9 @@ cylinder_t *get_or_create_cylinder(struct dive *d, int idx)
 		report_info("Warning: accessing invalid cylinder %d", idx);
 		return NULL;
 	}
-	while (idx >= d->cylinders.nr)
+	while (static_cast<size_t>(idx) >= d->cylinders.size())
 		add_empty_cylinder(&d->cylinders);
-	return &d->cylinders.cylinders[idx];
+	return &d->cylinders[idx];
 }
 
 /* if a default cylinder is set, use that */
@@ -465,7 +447,7 @@ void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
 		return;
 	for (auto &ti: tank_info_table) {
 		if (ti.name == cyl_name) {
-			cyl->type.description = strdup(ti.name.c_str());
+			cyl->type.description = ti.name;
 			if (ti.ml) {
 				cyl->type.size.mliter = ti.ml;
 				cyl->type.workingpressure.mbar = ti.bar * 1000;
@@ -481,10 +463,16 @@ void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl)
 	}
 }
 
+cylinder_t default_cylinder(const struct dive *d)
+{
+	cylinder_t res;
+	fill_default_cylinder(d, &res);
+	return res;
+}
+
 cylinder_t create_new_cylinder(const struct dive *d)
 {
-	cylinder_t cyl;
-	fill_default_cylinder(d, &cyl);
+	cylinder_t cyl = default_cylinder(d);
 	cyl.start = cyl.type.workingpressure;
 	cyl.cylinder_use = OC_GAS;
 	return cyl;
@@ -500,7 +488,7 @@ cylinder_t create_new_manual_cylinder(const struct dive *d)
 void add_default_cylinder(struct dive *d)
 {
 	// Only add if there are no cylinders yet
-	if (d->cylinders.nr > 0)
+	if (!d->cylinders.empty())
 		return;
 
 	cylinder_t cyl;
@@ -508,7 +496,7 @@ void add_default_cylinder(struct dive *d)
 		cyl = create_new_cylinder(d);
 	} else {
 		// roughly an AL80
-		cyl.type.description = strdup(translate("gettextFromC", "unknown"));
+		cyl.type.description = translate("gettextFromC", "unknown");
 		cyl.type.size.mliter = 11100;
 		cyl.type.workingpressure.mbar = 207000;
 	}
@@ -521,11 +509,11 @@ static bool show_cylinder(const struct dive *d, int i)
 	if (is_cylinder_used(d, i))
 		return true;
 
-	const cylinder_t *cyl = &d->cylinders.cylinders[i];
-	if (cyl->start.mbar || cyl->sample_start.mbar ||
-	    cyl->end.mbar || cyl->sample_end.mbar)
+	const cylinder_t &cyl = d->cylinders[i];
+	if (cyl.start.mbar || cyl.sample_start.mbar ||
+	    cyl.end.mbar || cyl.sample_end.mbar)
 		return true;
-	if (cyl->manually_added)
+	if (cyl.manually_added)
 		return true;
 
 	/*
@@ -538,10 +526,10 @@ static bool show_cylinder(const struct dive *d, int i)
 /* The unused cylinders at the end of the cylinder list are hidden. */
 int first_hidden_cylinder(const struct dive *d)
 {
-	int res = d->cylinders.nr;
+	size_t res = d->cylinders.size();
 	while (res > 0 && !show_cylinder(d, res - 1))
 		--res;
-	return res;
+	return static_cast<int>(res);
 }
 
 #ifdef DEBUG_CYL
@@ -551,7 +539,7 @@ void dump_cylinders(struct dive *dive, bool verbose)
 	for (int i = 0; i < dive->cylinders; i++) {
 		cylinder_t *cyl = get_cylinder(dive, i);
 
-		printf("%02d: Type     %s, %3.1fl, %3.0fbar\n", i, cyl->type.description, cyl->type.size.mliter / 1000.0, cyl->type.workingpressure.mbar / 1000.0);
+		printf("%02d: Type     %s, %3.1fl, %3.0fbar\n", i, cyl->type.description.c_str(), cyl->type.size.mliter / 1000.0, cyl->type.workingpressure.mbar / 1000.0);
 		printf("    Gasmix   O2 %2.0f%% He %2.0f%%\n", cyl->gasmix.o2.permille / 10.0, cyl->gasmix.he.permille / 10.0);
 		printf("    Pressure Start %3.0fbar End %3.0fbar Sample start %3.0fbar Sample end %3.0fbar\n", cyl->start.mbar / 1000.0, cyl->end.mbar / 1000.0, cyl->sample_start.mbar / 1000.0, cyl->sample_end.mbar / 1000.0);
 		if (verbose) {
diff --git a/core/equipment.h b/core/equipment.h
index 09ed5e4cd..ba2e5b278 100644
--- a/core/equipment.h
+++ b/core/equipment.h
@@ -17,7 +17,7 @@ struct cylinder_type_t
 {
 	volume_t size;
 	pressure_t workingpressure;
-	const char *description = nullptr; /* "LP85", "AL72", "AL80", "HP100+" or whatever */
+	std::string description; /* "LP85", "AL72", "AL80", "HP100+" or whatever */
 };
 
 struct cylinder_t
@@ -32,17 +32,23 @@ struct cylinder_t
 	enum cylinderuse cylinder_use = OC_GAS;
 	bool bestmix_o2 = false;
 	bool bestmix_he = false;
+
+	cylinder_t();
+	~cylinder_t();
 };
 
-/* Table of cylinders. Attention: this stores cylinders,
- * *not* pointers to cylinders. This has two crucial consequences:
- * 1) Pointers to cylinders are not stable. They may be
- *    invalidated if the table is reallocated.
- * 2) add_cylinder(), etc. take ownership of the
- *    cylinder. Notably of the description string. */
-struct cylinder_table {
-	int nr, allocated;
-	cylinder_t *cylinders;
+/* Table of cylinders.
+ * This is a crazy class: it is basically a std::vector<>, but overrides
+ * the [] accessor functions and allows out-of-bound accesses.
+ * This is used in the planner, which uses "max_index + 1" for the
+ * surface air cylinder.
+ * Note: an out-of-bound access returns a reference to an object with
+ * static linkage that MUST NOT be written into.
+ * Yes, this is all very mad, but it grew historically.
+ */
+struct cylinder_table : public std::vector<cylinder_t> {
+	cylinder_t &operator[](size_t i);
+	const cylinder_t &operator[](size_t i) const;
 };
 
 struct weightsystem_t
@@ -68,16 +74,13 @@ struct weightsystem_table {
 
 extern enum cylinderuse cylinderuse_from_text(const char *text);
 extern void copy_weights(const struct weightsystem_table *s, struct weightsystem_table *d);
-extern void copy_cylinders(const struct cylinder_table *s, struct cylinder_table *d);
 extern weightsystem_t clone_weightsystem(weightsystem_t ws);
 extern void free_weightsystem(weightsystem_t ws);
 extern void copy_cylinder_types(const struct dive *s, struct dive *d);
 extern void add_cloned_weightsystem(struct weightsystem_table *t, weightsystem_t ws);
-extern cylinder_t clone_cylinder(cylinder_t cyl);
-extern void free_cylinder(cylinder_t cyl);
 extern cylinder_t *add_empty_cylinder(struct cylinder_table *t);
-extern void add_cloned_cylinder(struct cylinder_table *t, cylinder_t cyl);
-extern cylinder_t *get_cylinder(const struct dive *d, int idx);
+extern cylinder_t *get_cylinder(struct dive *d, int idx);
+extern const cylinder_t *get_cylinder(const struct dive *d, int idx);
 extern cylinder_t *get_or_create_cylinder(struct dive *d, int idx);
 extern bool same_weightsystem(weightsystem_t w1, weightsystem_t w2);
 extern void remove_cylinder(struct dive *dive, int idx);
@@ -85,8 +88,9 @@ extern void remove_weightsystem(struct dive *dive, int idx);
 extern void set_weightsystem(struct dive *dive, int idx, weightsystem_t ws);
 extern void reset_cylinders(struct dive *dive, bool track_gas);
 extern int gas_volume(const cylinder_t *cyl, pressure_t p); /* Volume in mliter of a cylinder at pressure 'p' */
-extern int find_best_gasmix_match(struct gasmix mix, const struct cylinder_table *cylinders);
+extern int find_best_gasmix_match(struct gasmix mix, const struct cylinder_table &cylinders);
 extern void fill_default_cylinder(const struct dive *dive, cylinder_t *cyl); /* dive is needed to fill out MOD, which depends on salinity. */
+extern cylinder_t default_cylinder(const struct dive *d);
 extern cylinder_t create_new_manual_cylinder(const struct dive *dive); /* dive is needed to fill out MOD, which depends on salinity. */
 extern void add_default_cylinder(struct dive *dive);
 extern int first_hidden_cylinder(const struct dive *d);
@@ -99,7 +103,6 @@ extern void clear_weightsystem_table(struct weightsystem_table *);
 extern void add_to_weightsystem_table(struct weightsystem_table *, int idx, weightsystem_t ws);
 
 /* Cylinder table functions */
-extern void clear_cylinder_table(struct cylinder_table *);
 extern void add_cylinder(struct cylinder_table *, int idx, cylinder_t cyl);
 
 void get_gas_string(struct gasmix gasmix, char *text, int len);
diff --git a/core/filterconstraint.cpp b/core/filterconstraint.cpp
index 2a2ffe448..8dbc066ae 100644
--- a/core/filterconstraint.cpp
+++ b/core/filterconstraint.cpp
@@ -857,8 +857,8 @@ static bool has_weight_type(const filter_constraint &c, const struct dive *d)
 static bool has_cylinder_type(const filter_constraint &c, const struct dive *d)
 {
 	QStringList cylinderTypes;
-	for (int i = 0; i < d->cylinders.nr; ++i)
-		cylinderTypes.push_back(d->cylinders.cylinders[i].type.description);
+	for (const cylinder_t &cyl: d->cylinders)
+		cylinderTypes.push_back(QString::fromStdString(cyl.type.description));
 
 	return check(c, cylinderTypes);
 }
@@ -904,22 +904,15 @@ static bool check_numerical_range_non_zero(const filter_constraint &c, int v)
 
 static bool check_cylinder_size(const filter_constraint &c, const struct dive *d)
 {
-	for (int i = 0; i < d->cylinders.nr; ++i) {
-		const cylinder_t &cyl = d->cylinders.cylinders[i];
-		if (cyl.type.size.mliter && check_numerical_range(c, cyl.type.size.mliter))
-			return true;
-	}
-	return false;
+	return std::any_of(d->cylinders.begin(), d->cylinders.end(), [&c](auto &cyl)
+			   { return cyl.type.size.mliter &&
+				    check_numerical_range(c, cyl.type.size.mliter); });
 }
 
 static bool check_gas_range(const filter_constraint &c, const struct dive *d, gas_component component)
 {
-	for (int i = 0; i < d->cylinders.nr; ++i) {
-		const cylinder_t &cyl = d->cylinders.cylinders[i];
-		if (check_numerical_range(c, get_gas_component_fraction(cyl.gasmix, component).permille))
-			return true;
-	}
-	return false;
+	return std::any_of(d->cylinders.begin(), d->cylinders.end(), [&c, &component](auto &cyl)
+			   { return check_numerical_range(c, get_gas_component_fraction(cyl.gasmix, component).permille); });
 }
 
 static long days_since_epoch(timestamp_t timestamp)
diff --git a/core/fulltext.cpp b/core/fulltext.cpp
index 563d6967c..b010f25ab 100644
--- a/core/fulltext.cpp
+++ b/core/fulltext.cpp
@@ -125,10 +125,8 @@ static std::vector<QString> getWords(const dive *d)
 	tokenize(QString(d->suit), res);
 	for (const tag_entry *tag = d->tag_list; tag; tag = tag->next)
 		tokenize(QString::fromStdString(tag->tag->name), res);
-	for (int i = 0; i < d->cylinders.nr; ++i) {
-		const cylinder_t &cyl = *get_cylinder(d, i);
-		tokenize(QString(cyl.type.description), res);
-	}
+	for (auto &cyl: d->cylinders)
+		tokenize(QString::fromStdString(cyl.type.description), res);
 	for (int i = 0; i < d->weightsystems.nr; ++i) {
 		const weightsystem_t &ws = d->weightsystems.weightsystems[i];
 		tokenize(QString(ws.description), res);
diff --git a/core/gas.cpp b/core/gas.cpp
index 823bb9803..398a2127c 100644
--- a/core/gas.cpp
+++ b/core/gas.cpp
@@ -40,20 +40,20 @@ int same_gasmix(struct gasmix a, struct gasmix b)
 	return get_o2(a) == get_o2(b) && get_he(a) == get_he(b);
 }
 
-void sanitize_gasmix(struct gasmix *mix)
+void sanitize_gasmix(struct gasmix &mix)
 {
 	unsigned int o2, he;
 
-	o2 = get_o2(*mix);
-	he = get_he(*mix);
+	o2 = get_o2(mix);
+	he = get_he(mix);
 
 	/* Regular air: leave empty */
 	if (!he) {
 		if (!o2)
 			return;
 		/* 20.8% to 21% O2 is just air */
-		if (gasmix_is_air(*mix)) {
-			mix->o2.permille = 0;
+		if (gasmix_is_air(mix)) {
+			mix.o2.permille = 0;
 			return;
 		}
 	}
@@ -62,7 +62,7 @@ void sanitize_gasmix(struct gasmix *mix)
 	if (o2 <= 1000 && he <= 1000 && o2 + he <= 1000)
 		return;
 	report_info("Odd gasmix: %u O2 %u He", o2, he);
-	*mix = gasmix_air;
+	mix = gasmix_air;
 }
 
 int gasmix_distance(struct gasmix a, struct gasmix b)
diff --git a/core/gas.h b/core/gas.h
index 8a8352be0..4e6bcf193 100644
--- a/core/gas.h
+++ b/core/gas.h
@@ -58,7 +58,7 @@ struct gas_pressures {
 	double o2 = 0.0, n2 = 0.0, he = 0.0;
 };
 
-extern void sanitize_gasmix(struct gasmix *mix);
+extern void sanitize_gasmix(struct gasmix &mix);
 extern int gasmix_distance(struct gasmix a, struct gasmix b);
 extern fraction_t get_gas_component_fraction(struct gasmix mix, enum gas_component component);
 extern gas_pressures fill_pressures(double amb_pressure, struct gasmix mix, double po2, enum divemode_t dctype);
diff --git a/core/gaspressures.cpp b/core/gaspressures.cpp
index 0179f18ff..0f241f4b1 100644
--- a/core/gaspressures.cpp
+++ b/core/gaspressures.cpp
@@ -310,13 +310,13 @@ static void debug_print_pressures(struct plot_info &pi)
 void populate_pressure_information(const struct dive *dive, const struct divecomputer *dc, struct plot_info &pi, int sensor)
 {
 	int first, last, cyl;
-	cylinder_t *cylinder = get_cylinder(dive, sensor);
+	const cylinder_t *cylinder = get_cylinder(dive, sensor);
 	std::vector<pr_track_t> track;
 	size_t current = std::string::npos;
 	int missing_pr = 0, dense = 1;
 	const double gasfactor[5] = {1.0, 0.0, prefs.pscr_ratio/1000.0, 1.0, 1.0 };
 
-	if (sensor < 0 || sensor >= dive->cylinders.nr)
+	if (sensor < 0 || static_cast<size_t>(sensor) >= dive->cylinders.size())
 		return;
 
 	/* if we have no pressure data whatsoever, this is pointless, so let's just return */
diff --git a/core/import-csv.cpp b/core/import-csv.cpp
index 56d6849b5..347b52ab4 100644
--- a/core/import-csv.cpp
+++ b/core/import-csv.cpp
@@ -494,7 +494,6 @@ int parse_txt_file(const char *filename, const char *csv, struct divelog *log)
 		bool has_depth = false, has_setpoint = false, has_ndl = false;
 		char *lineptr;
 		int prev_time = 0;
-		cylinder_t cyl;
 
 		struct divecomputer *dc;
 		struct tm cur_tm;
@@ -517,26 +516,32 @@ int parse_txt_file(const char *filename, const char *csv, struct divelog *log)
 		dive->dcs[0].divemode = CCR;
 		dive->dcs[0].no_o2sensors = 2;
 
-		cyl.cylinder_use = OXYGEN;
-		cyl.type.size.mliter = 3000;
-		cyl.type.workingpressure.mbar = 200000;
-		cyl.type.description = "3l Mk6";
-		cyl.gasmix.o2.permille = 1000;
-		cyl.manually_added = true;
-		cyl.bestmix_o2 = 0;
-		cyl.bestmix_he = 0;
-		add_cloned_cylinder(&dive->cylinders, cyl);
+		{
+			cylinder_t cyl;
+			cyl.cylinder_use = OXYGEN;
+			cyl.type.size.mliter = 3000;
+			cyl.type.workingpressure.mbar = 200000;
+			cyl.type.description = "3l Mk6";
+			cyl.gasmix.o2.permille = 1000;
+			cyl.manually_added = true;
+			cyl.bestmix_o2 = 0;
+			cyl.bestmix_he = 0;
+			dive->cylinders.push_back(std::move(cyl));
+		}
 
-		cyl.cylinder_use = DILUENT;
-		cyl.type.size.mliter = 3000;
-		cyl.type.workingpressure.mbar = 200000;
-		cyl.type.description = "3l Mk6";
-		value = parse_mkvi_value(memtxt.data(), "Helium percentage");
-		he = atoi(value.c_str());
-		value = parse_mkvi_value(memtxt.data(), "Nitrogen percentage");
-		cyl.gasmix.o2.permille = (100 - atoi(value.c_str()) - he) * 10;
-		cyl.gasmix.he.permille = he * 10;
-		add_cloned_cylinder(&dive->cylinders, cyl);
+		{
+			cylinder_t cyl;
+			cyl.cylinder_use = DILUENT;
+			cyl.type.size.mliter = 3000;
+			cyl.type.workingpressure.mbar = 200000;
+			cyl.type.description = "3l Mk6";
+			value = parse_mkvi_value(memtxt.data(), "Helium percentage");
+			he = atoi(value.c_str());
+			value = parse_mkvi_value(memtxt.data(), "Nitrogen percentage");
+			cyl.gasmix.o2.permille = (100 - atoi(value.c_str()) - he) * 10;
+			cyl.gasmix.he.permille = he * 10;
+			dive->cylinders.push_back(std::move(cyl));
+		}
 
 		lineptr = strstr(memtxt.data(), "Dive started at");
 		while (!empty_string(lineptr) && (lineptr = strchr(lineptr, '\n'))) {
diff --git a/core/import-divinglog.cpp b/core/import-divinglog.cpp
index 6907caeb7..2ff967cdd 100644
--- a/core/import-divinglog.cpp
+++ b/core/import-divinglog.cpp
@@ -130,7 +130,7 @@ static int divinglog_profile(void *param, int, char **data, char **)
 			state->cur_sample->temperature.mkelvin = C_to_mkelvin(temp / 10.0f);
 			state->cur_sample->pressure[0].mbar = pressure * 100;
 			state->cur_sample->rbt.seconds = rbt;
-			if (oldcyl != tank && tank >= 0 && tank < state->cur_dive->cylinders.nr) {
+			if (oldcyl != tank && tank >= 0 && static_cast<size_t>(tank) < state->cur_dive->cylinders.size()) {
 				struct gasmix mix = get_cylinder(state->cur_dive.get(), tank)->gasmix;
 				int o2 = get_o2(mix);
 				int he = get_he(mix);
diff --git a/core/import-shearwater.cpp b/core/import-shearwater.cpp
index 5ce5bbc3d..077feec09 100644
--- a/core/import-shearwater.cpp
+++ b/core/import-shearwater.cpp
@@ -58,24 +58,20 @@ static int shearwater_changes(void *param, int columns, char **data, char **)
 		o2 = 1000;
 
 	// Find the cylinder index
-	int index;
-	bool found = false;
-	for (index = 0; index < state->cur_dive->cylinders.nr; ++index) {
-		const cylinder_t *cyl = get_cylinder(state->cur_dive.get(), index);
-		if (cyl->gasmix.o2.permille == o2 && cyl->gasmix.he.permille == he) {
-			found = true;
-			break;
-		}
-	}
-	if (!found) {
+	auto it = std::find_if(state->cur_dive->cylinders.begin(), state->cur_dive->cylinders.end(),
+			      [o2, he](auto &cyl)
+			      { return cyl.gasmix.o2.permille == o2 && cyl.gasmix.he.permille == he; });
+	if (it == state->cur_dive->cylinders.end()) {
 		// Cylinder not found, creating a new one
 		cyl = cylinder_start(state);
 		cyl->gasmix.o2.permille = o2;
 		cyl->gasmix.he.permille = he;
 		cylinder_end(state);
+		it = std::prev(state->cur_dive->cylinders.end());
 	}
 
-	add_gas_switch_event(state->cur_dive.get(), get_dc(state), state->sample_rate ? atoi(data[0]) / state->sample_rate * 10 : atoi(data[0]), index);
+	add_gas_switch_event(state->cur_dive.get(), get_dc(state), state->sample_rate ? atoi(data[0]) / state->sample_rate * 10 : atoi(data[0]),
+			     it - state->cur_dive->cylinders.begin());
 	return 0;
 }
 
@@ -103,9 +99,8 @@ static int shearwater_profile_sample(void *param, int, char **data, char **)
 		state->cur_sample->depth.mm = state->metric ? lrint(permissive_strtod(data[1], NULL) * 1000) : feet_to_mm(permissive_strtod(data[1], NULL));
 	if (data[2])
 		state->cur_sample->temperature.mkelvin = state->metric ? C_to_mkelvin(permissive_strtod(data[2], NULL)) : F_to_mkelvin(permissive_strtod(data[2], NULL));
-	if (data[3]) {
+	if (data[3])
 		state->cur_sample->setpoint.mbar = lrint(permissive_strtod(data[3], NULL) * 1000);
-	}
 	if (data[4])
 		state->cur_sample->ndl.seconds = atoi(data[4]) * 60;
 	if (data[5])
diff --git a/core/libdivecomputer.cpp b/core/libdivecomputer.cpp
index 2bf817a45..0efed9f32 100644
--- a/core/libdivecomputer.cpp
+++ b/core/libdivecomputer.cpp
@@ -165,7 +165,7 @@ static dc_status_t parse_gasmixes(device_data_t *devdata, struct dive *dive, dc_
 		bottom_gas = gasmix_air;
 	}
 
-	clear_cylinder_table(&dive->cylinders);
+	dive->cylinders.clear();
 	for (i = 0; i < std::max(ngases, ntanks); i++) {
 		cylinder_t cyl;
 		cyl.cylinder_use = NOT_USED;
@@ -266,7 +266,7 @@ static dc_status_t parse_gasmixes(device_data_t *devdata, struct dive *dive, dc_
 							snprintf(name_buffer, sizeof(name_buffer), "%d cuft", rounded_size);
 							break;
 						}
-						cyl.type.description = copy_string(name_buffer);
+						cyl.type.description = name_buffer;
 						cyl.type.size.mliter = lrint(cuft_to_l(rounded_size) * 1000 /
 											mbar_to_atm(cyl.type.workingpressure.mbar));
 					}
@@ -301,10 +301,10 @@ static dc_status_t parse_gasmixes(device_data_t *devdata, struct dive *dive, dc_
 			fill_default_cylinder(dive, &cyl);
 		}
 		/* whatever happens, make sure there is a name for the cylinder */
-		if (empty_string(cyl.type.description))
-			cyl.type.description = strdup(translate("gettextFromC", "unknown"));
+		if (cyl.type.description.empty())
+			cyl.type.description = translate("gettextFromC", "unknown");
 
-		add_cylinder(&dive->cylinders, dive->cylinders.nr, cyl);
+		dive->cylinders.push_back(std::move(cyl));
 	}
 	return DC_STATUS_SUCCESS;
 }
diff --git a/core/liquivision.cpp b/core/liquivision.cpp
index ef2203596..0147b9468 100644
--- a/core/liquivision.cpp
+++ b/core/liquivision.cpp
@@ -147,8 +147,7 @@ static void parse_dives(int log_version, const unsigned char *buf, unsigned int
 
 		/* Just the main cylinder until we can handle the buddy cylinder porperly */
 		for (i = 0; i < 1; i++) {
-			cylinder_t cyl;
-			fill_default_cylinder(dive.get(), &cyl);
+			cylinder_t cyl = default_cylinder(dive.get());
 			add_cylinder(&dive->cylinders, i, cyl);
 		}
 
diff --git a/core/load-git.cpp b/core/load-git.cpp
index 8e47da3eb..4fa832644 100644
--- a/core/load-git.cpp
+++ b/core/load-git.cpp
@@ -389,7 +389,7 @@ static void parse_cylinder_keyvalue(void *_cylinder, const char *key, const std:
 		return;
 	}
 	if (!strcmp(key, "description")) {
-		cylinder->type.description = strdup(value.c_str());
+		cylinder->type.description = value;
 		return;
 	}
 	if (!strcmp(key, "o2")) {
@@ -444,9 +444,9 @@ static void parse_dive_cylinder(char *line, struct git_parser_state *state)
 		line = parse_keyvalue_entry(parse_cylinder_keyvalue, &cylinder, line, state);
 	}
 	if (cylinder.cylinder_use == OXYGEN)
-		state->o2pressure_sensor = state->active_dive->cylinders.nr;
+		state->o2pressure_sensor = static_cast<int>(state->active_dive->cylinders.size());
 
-	add_cylinder(&state->active_dive->cylinders, state->active_dive->cylinders.nr, cylinder);
+	state->active_dive->cylinders.push_back(std::move(cylinder));
 }
 
 static void parse_weightsystem_keyvalue(void *_ws, const char *key, const std::string &value)
@@ -655,7 +655,7 @@ static char *parse_sample_unit(struct sample *sample, double val, char *unit)
  */
 static int sanitize_sensor_id(const struct dive *d, int nr)
 {
-	return d && nr >= 0 && nr < d->cylinders.nr ? nr : NO_SENSOR;
+	return d && nr >= 0 && static_cast<size_t>(nr) < d->cylinders.size() ? nr : NO_SENSOR;
 }
 
 /*
diff --git a/core/parse-xml.cpp b/core/parse-xml.cpp
index b67827586..ce1dfa263 100644
--- a/core/parse-xml.cpp
+++ b/core/parse-xml.cpp
@@ -32,6 +32,7 @@
 #include "membuffer.h"
 #include "picture.h"
 #include "qthelper.h"
+#include "range.h"
 #include "sample.h"
 #include "tag.h"
 #include "xmlparams.h"
@@ -233,7 +234,7 @@ static void cylinder_use(const char *buffer, enum cylinderuse *cyl_use, struct p
 		enum cylinderuse use = cylinderuse_from_text(trimmed.c_str());
 		*cyl_use = use;
 		if (use == OXYGEN)
-			state->o2pressure_sensor = state->cur_dive->cylinders.nr - 1;
+			state->o2pressure_sensor = static_cast<int>(state->cur_dive->cylinders.size()) - 1;
 	}
 }
 
@@ -990,10 +991,8 @@ static int divinglog_dive_match(struct dive *dive, const char *name, char *buf,
 {
 	/* For cylinder related fields, we might have to create a cylinder first. */
 	cylinder_t cyl;
-	if (MATCH("tanktype", utf8_string, (char **)&cyl.type.description)) {
-		cylinder_t *cyl0 = get_or_create_cylinder(dive, 0);
-		free((void *)cyl0->type.description);
-		cyl0->type.description = cyl.type.description;
+	if (MATCH("tanktype", utf8_string_std, &cyl.type.description)) {
+		get_or_create_cylinder(dive, 0)->type.description = std::move(cyl.type.description);
 		return 1;
 	}
 	if (MATCH("tanksize", cylindersize, &cyl.type.size)) {
@@ -1230,7 +1229,7 @@ static void gps_picture_location(const char *buffer, struct picture *pic)
 /* We're in the top-level dive xml. Try to convert whatever value to a dive value */
 static void try_to_fill_dive(struct dive *dive, const char *name, char *buf, struct parser_state *state)
 {
-	cylinder_t *cyl = dive->cylinders.nr > 0 ? get_cylinder(dive, dive->cylinders.nr - 1) : NULL;
+	cylinder_t *cyl = !dive->cylinders.empty() ? &dive->cylinders.back() : NULL;
 	weightsystem_t *ws = dive->weightsystems.nr > 0 ?
 		&dive->weightsystems.weightsystems[dive->weightsystems.nr - 1] : NULL;
 	pressure_t p;
@@ -1356,7 +1355,7 @@ static void try_to_fill_dive(struct dive *dive, const char *name, char *buf, str
 			return;
 		if (MATCH_STATE("workpressure.cylinder", pressure, &cyl->type.workingpressure))
 			return;
-		if (MATCH("description.cylinder", utf8_string, (char **)&cyl->type.description))
+		if (MATCH("description.cylinder", utf8_string_std, &cyl->type.description))
 			return;
 		if (MATCH_STATE("start.cylinder", pressure, &cyl->start))
 			return;
@@ -1798,7 +1797,6 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 	unsigned char event;
 	bool found;
 	unsigned int time = 0;
-	int i;
 	char serial[6];
 	struct battery_status {
 		uint16_t volt1;
@@ -1971,11 +1969,10 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 				state.cur_event.type = SAMPLE_EVENT_GASCHANGE2;
 				state.cur_event.value = ptr[7] << 8 ^ ptr[6];
 
-				found = false;
-				for (i = 0; i < state.cur_dive->cylinders.nr; ++i) {
-					const cylinder_t *cyl = get_cylinder(state.cur_dive.get(), i);
-					if (cyl->gasmix.o2.permille == ptr[6] * 10 && cyl->gasmix.he.permille == ptr[7] * 10) {
+				for (const auto [i, cyl]: enumerated_range(state.cur_dive->cylinders)) {
+					if (cyl.gasmix.o2.permille == ptr[6] * 10 && cyl.gasmix.he.permille == ptr[7] * 10) {
 						found = true;
+						state.cur_event.gas.index = i;
 						break;
 					}
 				}
@@ -1984,9 +1981,7 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 					cyl->gasmix.o2.permille = ptr[6] * 10;
 					cyl->gasmix.he.permille = ptr[7] * 10;
 					cylinder_end(&state);
-					state.cur_event.gas.index = state.cur_dive->cylinders.nr - 1;
-				} else {
-					state.cur_event.gas.index = i;
+					state.cur_event.gas.index = static_cast<int>(state.cur_dive->cylinders.size()) - 1;
 				}
 				break;
 			case 6:
diff --git a/core/parse.cpp b/core/parse.cpp
index 6859d1299..9b8e100bd 100644
--- a/core/parse.cpp
+++ b/core/parse.cpp
@@ -335,7 +335,7 @@ void ws_end(struct parser_state *state)
  */
 static int sanitize_sensor_id(const struct dive *d, int nr)
 {
-	return d && nr >= 0 && nr < d->cylinders.nr ? nr : NO_SENSOR;
+	return d && nr >= 0 && static_cast<size_t>(nr) < d->cylinders.size() ? nr : NO_SENSOR;
 }
 
 /*
diff --git a/core/planner.cpp b/core/planner.cpp
index f6f856a43..3bf63227a 100644
--- a/core/planner.cpp
+++ b/core/planner.cpp
@@ -19,6 +19,7 @@
 #include "event.h"
 #include "interpolate.h"
 #include "planner.h"
+#include "range.h"
 #include "subsurface-time.h"
 #include "gettext.h"
 #include "libdivecomputer/parser.h"
@@ -94,7 +95,7 @@ int get_cylinderid_at_time(struct dive *dive, struct divecomputer *dc, duration_
 
 static int get_gasidx(struct dive *dive, struct gasmix mix)
 {
-	return find_best_gasmix_match(mix, &dive->cylinders);
+	return find_best_gasmix_match(mix, dive->cylinders);
 }
 
 static void interpolate_transition(struct deco_state *ds, struct dive *dive, duration_t t0, duration_t t1, depth_t d0, depth_t d1, struct gasmix gasmix, o2pressure_t po2, enum divemode_t divemode)
@@ -368,12 +369,12 @@ struct gaschanges {
 static int setpoint_change(struct dive *dive, int cylinderid)
 {
 	cylinder_t *cylinder = get_cylinder(dive, cylinderid);
-	if (!cylinder->type.description)
+	if (cylinder->type.description.empty())
 		return 0;
-	if (!strncmp(cylinder->type.description, "SP ", 3)) {
+	if (starts_with(cylinder->type.description, "SP ")) {
 		float sp;
-		sscanf(cylinder->type.description + 3, "%f", &sp);
-		return (int) (sp * 1000);
+		sscanf(cylinder->type.description.c_str() + 3, "%f", &sp);
+		return (int) (sp * 1000.0);
 	} else {
 		return 0;
 	}
@@ -572,10 +573,9 @@ static bool trial_ascent(struct deco_state *ds, int wait_time, int trial_depth,
  */
 static bool enough_gas(const struct dive *dive, int current_cylinder)
 {
-	cylinder_t *cyl;
-	if (current_cylinder < 0 || current_cylinder >= dive->cylinders.nr)
+	if (current_cylinder < 0 || static_cast<size_t>(current_cylinder) >= dive->cylinders.size())
 		return false;
-	cyl = get_cylinder(dive, current_cylinder);
+	const cylinder_t *cyl = get_cylinder(dive, current_cylinder);
 
 	if (!cyl->start.mbar)
 		return true;
@@ -1086,7 +1086,7 @@ bool plan(struct deco_state *ds, struct diveplan *diveplan, struct dive *dive, i
 		// we had a fixed cylinder table: It uses an extra fake cylinder
 		// past the regular cylinder table, which is not visible to the UI.
 		// Fix this as soon as possible!
-		current_cylinder = dive->cylinders.nr;
+		current_cylinder = static_cast<int>(dive->cylinders.size());
 		plan_add_segment(diveplan, prefs.surface_segment, 0, current_cylinder, 0, false, OC);
 	}
 	create_dive_from_plan(diveplan, dive, dc, is_planner);
diff --git a/core/plannernotes.cpp b/core/plannernotes.cpp
index b47b8101f..71f1577c8 100644
--- a/core/plannernotes.cpp
+++ b/core/plannernotes.cpp
@@ -16,6 +16,7 @@
 #include "units.h"
 #include "divelist.h"
 #include "planner.h"
+#include "range.h"
 #include "gettext.h"
 #include "libdivecomputer/parser.h"
 #include "qthelper.h"
@@ -461,34 +462,33 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 	}
 
 	/* Print gas consumption: This loop covers all cylinders */
-	for (int gasidx = 0; gasidx < dive->cylinders.nr; gasidx++) {
+	for (auto [gasidx, cyl]: enumerated_range(dive->cylinders)) {
 		double volume, pressure, deco_volume, deco_pressure, mingas_volume, mingas_pressure, mingas_d_pressure, mingas_depth;
 		const char *unit, *pressure_unit, *depth_unit;
 		std::string temp;
 		std::string warning;
 		std::string mingas;
-		cylinder_t *cyl = get_cylinder(dive, gasidx);
-		if (cyl->cylinder_use == NOT_USED)
+		if (cyl.cylinder_use == NOT_USED)
 			continue;
 
-		volume = get_volume_units(cyl->gas_used.mliter, NULL, &unit);
-		deco_volume = get_volume_units(cyl->deco_gas_used.mliter, NULL, &unit);
-		if (cyl->type.size.mliter) {
-			int remaining_gas = lrint((double)cyl->end.mbar * cyl->type.size.mliter / 1000.0 / gas_compressibility_factor(cyl->gasmix, cyl->end.mbar / 1000.0));
-			double deco_pressure_mbar = isothermal_pressure(cyl->gasmix, 1.0, remaining_gas + cyl->deco_gas_used.mliter,
-				cyl->type.size.mliter) * 1000 - cyl->end.mbar;
+		volume = get_volume_units(cyl.gas_used.mliter, NULL, &unit);
+		deco_volume = get_volume_units(cyl.deco_gas_used.mliter, NULL, &unit);
+		if (cyl.type.size.mliter) {
+			int remaining_gas = lrint((double)cyl.end.mbar * cyl.type.size.mliter / 1000.0 / gas_compressibility_factor(cyl.gasmix, cyl.end.mbar / 1000.0));
+			double deco_pressure_mbar = isothermal_pressure(cyl.gasmix, 1.0, remaining_gas + cyl.deco_gas_used.mliter,
+				cyl.type.size.mliter) * 1000 - cyl.end.mbar;
 			deco_pressure = get_pressure_units(lrint(deco_pressure_mbar), &pressure_unit);
-			pressure = get_pressure_units(cyl->start.mbar - cyl->end.mbar, &pressure_unit);
+			pressure = get_pressure_units(cyl.start.mbar - cyl.end.mbar, &pressure_unit);
 			/* Warn if the plan uses more gas than is available in a cylinder
 			 * This only works if we have working pressure for the cylinder
 			 * 10bar is a made up number - but it seemed silly to pretend you could breathe cylinder down to 0 */
-			if (cyl->end.mbar < 10000)
+			if (cyl.end.mbar < 10000)
 				warning = format_string_std("<br/>\n&nbsp;&mdash; <span style='color: red;'>%s </span> %s",
 					translate("gettextFromC", "Warning:"),
 					translate("gettextFromC", "this is more gas than available in the specified cylinder!"));
 			else
-				if (cyl->end.mbar / 1000.0 * cyl->type.size.mliter / gas_compressibility_factor(cyl->gasmix, cyl->end.mbar / 1000.0)
-				    < cyl->deco_gas_used.mliter)
+				if (cyl.end.mbar / 1000.0 * cyl.type.size.mliter / gas_compressibility_factor(cyl.gasmix, cyl.end.mbar / 1000.0)
+				    < cyl.deco_gas_used.mliter)
 					warning = format_string_std("<br/>\n&nbsp;&mdash; <span style='color: red;'>%s </span> %s",
 						translate("gettextFromC", "Warning:"),
 						translate("gettextFromC", "not enough reserve for gas sharing on ascent!"));
@@ -502,17 +502,17 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 					volume_t mingasv;
 					mingasv.mliter = lrint(prefs.sacfactor / 100.0 * prefs.problemsolvingtime * prefs.bottomsac
 						* depth_to_bar(lastbottomdp->depth.mm, dive)
-						+ prefs.sacfactor / 100.0 * cyl->deco_gas_used.mliter);
+						+ prefs.sacfactor / 100.0 * cyl.deco_gas_used.mliter);
 					/* Calculate minimum gas pressure for cyclinder. */
-					lastbottomdp->minimum_gas.mbar = lrint(isothermal_pressure(cyl->gasmix, 1.0,
-						mingasv.mliter, cyl->type.size.mliter) * 1000);
+					lastbottomdp->minimum_gas.mbar = lrint(isothermal_pressure(cyl.gasmix, 1.0,
+						mingasv.mliter, cyl.type.size.mliter) * 1000);
 					/* Translate all results into correct units */
 					mingas_volume = get_volume_units(mingasv.mliter, NULL, &unit);
 					mingas_pressure = get_pressure_units(lastbottomdp->minimum_gas.mbar, &pressure_unit);
-					mingas_d_pressure = get_pressure_units(lrint((double)cyl->end.mbar + deco_pressure_mbar - lastbottomdp->minimum_gas.mbar), &pressure_unit);
+					mingas_d_pressure = get_pressure_units(lrint((double)cyl.end.mbar + deco_pressure_mbar - lastbottomdp->minimum_gas.mbar), &pressure_unit);
 					mingas_depth = get_depth_units(lastbottomdp->depth.mm, NULL, &depth_unit);
 					/* Print it to results */
-					if (cyl->start.mbar > lastbottomdp->minimum_gas.mbar) {
+					if (cyl.start.mbar > lastbottomdp->minimum_gas.mbar) {
 						mingas = casprintf_loc("<br/>\n&nbsp;&mdash; <span style='color: %s;'>%s</span> (%s %.1fx%s/+%d%s@%.0f%s): "
 							     "%.0f%s/%.0f%s<span style='color: %s;'>/&Delta;:%+.0f%s</span>",
 							     mingas_d_pressure > 0 ? "green" :"red",
@@ -536,18 +536,18 @@ void add_plan_to_notes(struct diveplan *diveplan, struct dive *dive, bool show_d
 			/* Print the gas consumption for every cylinder here to temp buffer. */
 			if (lrint(volume) > 0) {
 				temp = casprintf_loc(translate("gettextFromC", "%.0f%s/%.0f%s of <span style='color: red;'><b>%s</b></span> (%.0f%s/%.0f%s in planned ascent)"),
-					     volume, unit, pressure, pressure_unit, gasname(cyl->gasmix), deco_volume, unit, deco_pressure, pressure_unit);
+					     volume, unit, pressure, pressure_unit, gasname(cyl.gasmix), deco_volume, unit, deco_pressure, pressure_unit);
 			} else {
 				temp = casprintf_loc(translate("gettextFromC", "%.0f%s/%.0f%s of <span style='color: red;'><b>%s</b></span>"),
-					     volume, unit, pressure, pressure_unit, gasname(cyl->gasmix));
+					     volume, unit, pressure, pressure_unit, gasname(cyl.gasmix));
 			}
 		} else {
 			if (lrint(volume) > 0) {
 				temp = casprintf_loc(translate("gettextFromC", "%.0f%s of <span style='color: red;'><b>%s</b></span> (%.0f%s during planned ascent)"),
-					     volume, unit, gasname(cyl->gasmix), deco_volume, unit);
+					     volume, unit, gasname(cyl.gasmix), deco_volume, unit);
 			} else {
 				temp = casprintf_loc(translate("gettextFromC", "%.0f%s of <span style='color: red;'><b>%s</b></span>"),
-					     volume, unit, gasname(cyl->gasmix));
+					     volume, unit, gasname(cyl.gasmix));
 			}
 		}
 		/* Gas consumption: Now finally print all strings to output */
diff --git a/core/profile.cpp b/core/profile.cpp
index fffb6108a..b59f19930 100644
--- a/core/profile.cpp
+++ b/core/profile.cpp
@@ -24,6 +24,7 @@
 #include "libdivecomputer/version.h"
 #include "membuffer.h"
 #include "qthelper.h"
+#include "range.h"
 #include "format.h"
 
 //#define DEBUG_GAS 1
@@ -216,7 +217,7 @@ int get_cylinder_index(const struct dive *dive, const struct event &ev)
 	report_info("Still looking up cylinder based on gas mix in get_cylinder_index()!");
 
 	mix = get_gasmix_from_event(dive, ev);
-	best = find_best_gasmix_match(mix, &dive->cylinders);
+	best = find_best_gasmix_match(mix, dive->cylinders);
 	return best < 0 ? 0 : best;
 }
 
@@ -259,12 +260,11 @@ static void calculate_max_limits_new(const struct dive *dive, const struct divec
 	int maxhr = 0, minhr = INT_MAX;
 	int mintemp = dive->mintemp.mkelvin;
 	int maxtemp = dive->maxtemp.mkelvin;
-	int cyl;
 
 	/* Get the per-cylinder maximum pressure if they are manual */
-	for (cyl = 0; cyl < dive->cylinders.nr; cyl++) {
-		int mbar_start = get_cylinder(dive, cyl)->start.mbar;
-		int mbar_end = get_cylinder(dive, cyl)->end.mbar;
+	for (auto &cyl: dive->cylinders) {
+		int mbar_start = cyl.start.mbar;
+		int mbar_end = cyl.end.mbar;
 		if (mbar_start > maxpressure)
 			maxpressure = mbar_start;
 		if (mbar_end && mbar_end < minpressure)
@@ -364,7 +364,7 @@ static void insert_entry(struct plot_info &pi, int time, int depth, int sac)
 
 static void populate_plot_entries(const struct dive *dive, const struct divecomputer *dc, struct plot_info &pi)
 {
-	pi.nr_cylinders = dive->cylinders.nr;
+	pi.nr_cylinders = static_cast<int>(dive->cylinders.size());
 
 	/*
 	 * To avoid continuous reallocation, allocate the expected number of entries.
@@ -494,26 +494,21 @@ static void populate_plot_entries(const struct dive *dive, const struct divecomp
  */
 static int sac_between(const struct dive *dive, const struct plot_info &pi, int first, int last, const char gases[])
 {
-	int i, airuse;
-	double pressuretime;
-
 	if (first == last)
 		return 0;
 
 	/* Get airuse for the set of cylinders over the range */
-	airuse = 0;
-	for (i = 0; i < pi.nr_cylinders; i++) {
+	int airuse = 0;
+	for (int i = 0; i < pi.nr_cylinders; i++) {
 		pressure_t a, b;
-		cylinder_t *cyl;
-		int cyluse;
 
 		if (!gases[i])
 			continue;
 
 		a.mbar = get_plot_pressure(pi, first, i);
 		b.mbar = get_plot_pressure(pi, last, i);
-		cyl = get_cylinder(dive, i);
-		cyluse = gas_volume(cyl, a) - gas_volume(cyl, b);
+		const cylinder_t *cyl = get_cylinder(dive, i);
+		int cyluse = gas_volume(cyl, a) - gas_volume(cyl, b);
 		if (cyluse > 0)
 			airuse += cyluse;
 	}
@@ -521,7 +516,7 @@ static int sac_between(const struct dive *dive, const struct plot_info &pi, int
 		return 0;
 
 	/* Calculate depthpressure integrated over time */
-	pressuretime = 0.0;
+	double pressuretime = 0.0;
 	do {
 		const struct plot_data &entry = pi.entry[first];
 		const struct plot_data &next = pi.entry[first + 1];
@@ -632,8 +627,8 @@ static void fill_sac(const struct dive *dive, struct plot_info &pi, int idx, con
  */
 static void matching_gases(const struct dive *dive, struct gasmix gasmix, char gases[])
 {
-	for (int i = 0; i < dive->cylinders.nr; i++)
-		gases[i] = same_gasmix(gasmix, get_cylinder(dive, i)->gasmix);
+	for (auto [i, cyl]: enumerated_range(dive->cylinders))
+		gases[i] = same_gasmix(gasmix, cyl.gasmix);
 }
 
 static void calculate_sac(const struct dive *dive, const struct divecomputer *dc, struct plot_info &pi)
@@ -1536,7 +1531,7 @@ std::vector<std::string> compare_samples(const struct dive *d, const struct plot
 				if (last_pressures[cylinder_index]) {
 					bar_used[cylinder_index] += last_pressures[cylinder_index] - next_pressure;
 
-					cylinder_t *cyl = get_cylinder(d, cylinder_index);
+					const cylinder_t *cyl = get_cylinder(d, cylinder_index);
 
 					volumes_used[cylinder_index] += gas_volume(cyl, (pressure_t){ last_pressures[cylinder_index] }) - gas_volume(cyl, (pressure_t){ next_pressure });
 				}
@@ -1589,7 +1584,7 @@ std::vector<std::string> compare_samples(const struct dive *d, const struct plot
 			total_bar_used += bar_used[cylinder_index];
 			total_volume_used += volumes_used[cylinder_index];
 
-			cylinder_t *cyl = get_cylinder(d, cylinder_index);
+			const cylinder_t *cyl = get_cylinder(d, cylinder_index);
 			if (cyl->type.size.mliter) {
 				if (cylinder_volume.mliter && cylinder_volume.mliter != cyl->type.size.mliter) {
 					cylindersizes_are_identical = false;
diff --git a/core/profile.h b/core/profile.h
index e8a03a8fb..405bbc1a7 100644
--- a/core/profile.h
+++ b/core/profile.h
@@ -95,7 +95,7 @@ struct plot_info {
 	double maxpp = 0.0;
 	bool waypoint_above_ceiling = false;
 	std::vector<plot_data> entry;
-	std::vector<plot_pressure_data> pressures; /* cylinders.nr blocks of nr entries. */
+	std::vector<plot_pressure_data> pressures; /* cylinders.size() blocks of nr entries. */
 
 	plot_info();
 	~plot_info();
diff --git a/core/qthelper.cpp b/core/qthelper.cpp
index 87563bc0f..f0582d01a 100644
--- a/core/qthelper.cpp
+++ b/core/qthelper.cpp
@@ -12,6 +12,7 @@
 #include "version.h"
 #include "errorhelper.h"
 #include "planner.h"
+#include "range.h"
 #include "subsurface-time.h"
 #include "gettextfromc.h"
 #include "metadata.h"
@@ -357,11 +358,10 @@ static bool lessThan(const QPair<QString, int> &a, const QPair<QString, int> &b)
 
 QVector<QPair<QString, int>> selectedDivesGasUsed()
 {
-	int j;
 	QMap<QString, int> gasUsed;
 	for (dive *d: getDiveSelection()) {
 		std::vector<volume_t> diveGases = get_gas_used(d);
-		for (j = 0; j < d->cylinders.nr; j++) {
+		for (size_t j = 0; j < d->cylinders.size(); j++) {
 			if (diveGases[j].mliter) {
 				QString gasName = gasname(get_cylinder(d, j)->gasmix);
 				gasUsed[gasName] += diveGases[j].mliter;
@@ -1189,16 +1189,15 @@ QString get_gas_string(struct gasmix gas)
 QStringList get_dive_gas_list(const struct dive *d)
 {
 	QStringList list;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		const cylinder_t *cyl = get_cylinder(d, i);
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		/* Check if we have the same gasmix two or more times
 		 * If yes return more verbose string */
 		int same_gas = same_gasmix_cylinder(cyl, i, d, true);
 		if (same_gas == -1)
-			list.push_back(get_gas_string(cyl->gasmix));
+			list.push_back(get_gas_string(cyl.gasmix));
 		else
-			list.push_back(get_gas_string(cyl->gasmix) + QString(" (%1 %2 ").arg(gettextFromC::tr("cyl.")).arg(i + 1) +
-				cyl->type.description + ")");
+			list.push_back(get_gas_string(cyl.gasmix) + QStringLiteral(" (%1 %2 ").arg(gettextFromC::tr("cyl.")).arg(i + 1) +
+				QString::fromStdString(cyl.type.description) + ")");
 	}
 	return list;
 }
diff --git a/core/save-git.cpp b/core/save-git.cpp
index 5c27b0a77..ff8d489a9 100644
--- a/core/save-git.cpp
+++ b/core/save-git.cpp
@@ -141,28 +141,23 @@ static void put_gasmix(struct membuffer *b, struct gasmix mix)
 
 static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 {
-	int i, nr;
-
-	nr = nr_cylinders(dive);
-	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = get_cylinder(dive, i);
-		int volume = cylinder->type.size.mliter;
-		const char *description = cylinder->type.description;
-		int use = cylinder->cylinder_use;
+	for (auto &cyl: dive->cylinders) {
+		int volume = cyl.type.size.mliter;
+		int use = cyl.cylinder_use;
 
 		put_string(b, "cylinder");
 		if (volume)
 			put_milli(b, " vol=", volume, "l");
-		put_pressure(b, cylinder->type.workingpressure, " workpressure=", "bar");
-		show_utf8(b, " description=", description, "");
+		put_pressure(b, cyl.type.workingpressure, " workpressure=", "bar");
+		show_utf8(b, " description=", cyl.type.description.c_str(), "");
 		strip_mb(b);
-		put_gasmix(b, cylinder->gasmix);
-		put_pressure(b, cylinder->start, " start=", "bar");
-		put_pressure(b, cylinder->end, " end=", "bar");
+		put_gasmix(b, cyl.gasmix);
+		put_pressure(b, cyl.start, " start=", "bar");
+		put_pressure(b, cyl.end, " end=", "bar");
 		if (use > OC_GAS && use < NUM_GAS_USE)
 			show_utf8(b, " use=", cylinderuse_text[use], "");
-		if (cylinder->depth.mm != 0)
-			put_milli(b, " depth=", cylinder->depth.mm, "m");
+		if (cyl.depth.mm != 0)
+			put_milli(b, " depth=", cyl.depth.mm, "m");
 		put_string(b, "\n");
 	}
 }
diff --git a/core/save-html.cpp b/core/save-html.cpp
index 28ab7e579..9971d41fe 100644
--- a/core/save-html.cpp
+++ b/core/save-html.cpp
@@ -121,43 +121,40 @@ static void put_weightsystem_HTML(struct membuffer *b, const struct dive *dive)
 
 static void put_cylinder_HTML(struct membuffer *b, const struct dive *dive)
 {
-	int i, nr;
 	const char *separator = "\"Cylinders\":[";
-	nr = nr_cylinders(dive);
 
-	if (!nr)
+	if (dive->cylinders.empty())
 		put_string(b, separator);
 
-	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = get_cylinder(dive, i);
+	for (auto &cyl: dive->cylinders) {
 		put_format(b, "%s{", separator);
 		separator = ", ";
-		write_attribute(b, "Type", cylinder->type.description, ", ");
-		if (cylinder->type.size.mliter) {
-			int volume = cylinder->type.size.mliter;
-			if (prefs.units.volume == units::CUFT && cylinder->type.workingpressure.mbar)
-				volume = lrint(volume * bar_to_atm(cylinder->type.workingpressure.mbar / 1000.0));
+		write_attribute(b, "Type", cyl.type.description.c_str(), ", ");
+		if (cyl.type.size.mliter) {
+			int volume = cyl.type.size.mliter;
+			if (prefs.units.volume == units::CUFT && cyl.type.workingpressure.mbar)
+				volume = lrint(volume * bar_to_atm(cyl.type.workingpressure.mbar / 1000.0));
 			put_HTML_volume_units(b, volume, "\"Size\":\"", " \", ");
 		} else {
 			write_attribute(b, "Size", "--", ", ");
 		}
-		put_HTML_pressure_units(b, cylinder->type.workingpressure, "\"WPressure\":\"", " \", ");
+		put_HTML_pressure_units(b, cyl.type.workingpressure, "\"WPressure\":\"", " \", ");
 
-		if (cylinder->start.mbar) {
-			put_HTML_pressure_units(b, cylinder->start, "\"SPressure\":\"", " \", ");
+		if (cyl.start.mbar) {
+			put_HTML_pressure_units(b, cyl.start, "\"SPressure\":\"", " \", ");
 		} else {
 			write_attribute(b, "SPressure", "--", ", ");
 		}
 
-		if (cylinder->end.mbar) {
-			put_HTML_pressure_units(b, cylinder->end, "\"EPressure\":\"", " \", ");
+		if (cyl.end.mbar) {
+			put_HTML_pressure_units(b, cyl.end, "\"EPressure\":\"", " \", ");
 		} else {
 			write_attribute(b, "EPressure", "--", ", ");
 		}
 
-		if (cylinder->gasmix.o2.permille) {
-			put_format(b, "\"O2\":\"%u.%u%%\",", FRACTION_TUPLE(cylinder->gasmix.o2.permille, 10));
-			put_format(b, "\"He\":\"%u.%u%%\"", FRACTION_TUPLE(cylinder->gasmix.he.permille, 10));
+		if (cyl.gasmix.o2.permille) {
+			put_format(b, "\"O2\":\"%u.%u%%\",", FRACTION_TUPLE(cyl.gasmix.o2.permille, 10));
+			put_format(b, "\"He\":\"%u.%u%%\"", FRACTION_TUPLE(cyl.gasmix.he.permille, 10));
 		} else {
 			write_attribute(b, "O2", "Air", "");
 		}
diff --git a/core/save-xml.cpp b/core/save-xml.cpp
index db8ec819b..7ba8880be 100644
--- a/core/save-xml.cpp
+++ b/core/save-xml.cpp
@@ -177,28 +177,22 @@ static void put_gasmix(struct membuffer *b, struct gasmix mix)
 
 static void save_cylinder_info(struct membuffer *b, struct dive *dive)
 {
-	int i, nr;
-
-	nr = nr_cylinders(dive);
-
-	for (i = 0; i < nr; i++) {
-		cylinder_t *cylinder = get_cylinder(dive, i);
-		int volume = cylinder->type.size.mliter;
-		const char *description = cylinder->type.description;
-		int use = cylinder->cylinder_use;
+	for (auto &cyl: dive->cylinders) {
+		int volume = cyl.type.size.mliter;
+		int use = cyl.cylinder_use;
 
 		put_format(b, "  <cylinder");
 		if (volume)
 			put_milli(b, " size='", volume, " l'");
-		put_pressure(b, cylinder->type.workingpressure, " workpressure='", " bar'");
-		show_utf8(b, description, " description='", "'", 1);
-		put_gasmix(b, cylinder->gasmix);
-		put_pressure(b, cylinder->start, " start='", " bar'");
-		put_pressure(b, cylinder->end, " end='", " bar'");
+		put_pressure(b, cyl.type.workingpressure, " workpressure='", " bar'");
+		show_utf8(b, cyl.type.description.c_str(), " description='", "'", 1);
+		put_gasmix(b, cyl.gasmix);
+		put_pressure(b, cyl.start, " start='", " bar'");
+		put_pressure(b, cyl.end, " end='", " bar'");
 		if (use > OC_GAS && use < NUM_GAS_USE)
 			show_utf8(b, cylinderuse_text[use], " use='", "'", 1);
-		if (cylinder->depth.mm != 0)
-			put_milli(b, " depth='", cylinder->depth.mm, " m'");
+		if (cyl.depth.mm != 0)
+			put_milli(b, " depth='", cyl.depth.mm, " m'");
 		put_format(b, " />\n");
 	}
 }
diff --git a/core/statistics.cpp b/core/statistics.cpp
index 6b36209aa..501aad223 100644
--- a/core/statistics.cpp
+++ b/core/statistics.cpp
@@ -9,6 +9,7 @@
 #include "divelog.h"
 #include "event.h"
 #include "gettext.h"
+#include "range.h"
 #include "sample.h"
 #include "subsurface-time.h"
 #include "trip.h"
@@ -273,15 +274,14 @@ bool has_gaschange_event(const struct dive *dive, const struct divecomputer *dc,
 
 bool is_cylinder_used(const struct dive *dive, int idx)
 {
-	cylinder_t *cyl;
-	if (idx < 0 || idx >= dive->cylinders.nr)
+	if (idx < 0 || static_cast<size_t>(idx) >= dive->cylinders.size())
 		return false;
 
-	cyl = get_cylinder(dive, idx);
-	if ((cyl->start.mbar - cyl->end.mbar) > SOME_GAS)
+	const cylinder_t &cyl = dive->cylinders[idx];
+	if ((cyl.start.mbar - cyl.end.mbar) > SOME_GAS)
 		return true;
 
-	if ((cyl->sample_start.mbar - cyl->sample_end.mbar) > SOME_GAS)
+	if ((cyl.sample_start.mbar - cyl.sample_end.mbar) > SOME_GAS)
 		return true;
 
 	for (auto &dc: dive->dcs) {
@@ -295,7 +295,7 @@ bool is_cylinder_used(const struct dive *dive, int idx)
 
 bool is_cylinder_prot(const struct dive *dive, int idx)
 {
-	if (idx < 0 || idx >= dive->cylinders.nr)
+	if (idx < 0 || static_cast<size_t>(idx) >= dive->cylinders.size())
 		return false;
 
 	return std::any_of(dive->dcs.begin(), dive->dcs.end(),
@@ -303,18 +303,17 @@ bool is_cylinder_prot(const struct dive *dive, int idx)
 			   { return has_gaschange_event(dive, &dc, idx); });
 }
 
-/* Returns a vector with dive->cylinders.nr entries */
+/* Returns a vector with dive->cylinders.size() entries */
 std::vector<volume_t> get_gas_used(struct dive *dive)
 {
-	std::vector<volume_t> gases(dive->cylinders.nr);
-	for (int idx = 0; idx < dive->cylinders.nr; idx++) {
-		cylinder_t *cyl = get_cylinder(dive, idx);
+	std::vector<volume_t> gases(dive->cylinders.size());
+	for (auto [idx, cyl]: enumerated_range(dive->cylinders)) {
 		pressure_t start, end;
 
-		start = cyl->start.mbar ? cyl->start : cyl->sample_start;
-		end = cyl->end.mbar ? cyl->end : cyl->sample_end;
+		start = cyl.start.mbar ? cyl.start : cyl.sample_start;
+		end = cyl.end.mbar ? cyl.end : cyl.sample_end;
 		if (end.mbar && start.mbar > end.mbar)
-			gases[idx].mliter = gas_volume(cyl, start) - gas_volume(cyl, end);
+			gases[idx].mliter = gas_volume(&cyl, start) - gas_volume(&cyl, end);
 		else
 			gases[idx].mliter = 0;
 	}
@@ -327,7 +326,7 @@ std::vector<volume_t> get_gas_used(struct dive *dive)
 static std::pair<volume_t, volume_t> get_gas_parts(struct gasmix mix, volume_t vol, int o2_in_topup)
 {
 	if (gasmix_is_air(mix))
-		return { {0}, {0} };
+		return { volume_t() , volume_t() };
 
 	volume_t air = { (int)lrint(((double)vol.mliter * get_n2(mix)) / (1000 - o2_in_topup)) };
 	volume_t he = { (int)lrint(((double)vol.mliter * get_he(mix)) / 1000.0) };
diff --git a/core/string-format.cpp b/core/string-format.cpp
index 718865fa8..39f54de84 100644
--- a/core/string-format.cpp
+++ b/core/string-format.cpp
@@ -4,6 +4,7 @@
 #include "event.h"
 #include "format.h"
 #include "qthelper.h"
+#include "range.h"
 #include "subsurface-string.h"
 #include "trip.h"
 #include <QDateTime>
@@ -13,23 +14,21 @@
 enum returnPressureSelector { START_PRESSURE, END_PRESSURE };
 static QLocale loc;
 
-static QString getPressures(const struct dive *dive, int i, enum returnPressureSelector ret)
+static QString getPressures(const cylinder_t &cyl, enum returnPressureSelector ret)
 {
-	const cylinder_t *cyl = get_cylinder(dive, i);
-	QString fmt;
 	if (ret == START_PRESSURE) {
-		if (cyl->start.mbar)
-			fmt = get_pressure_string(cyl->start, true);
-		else if (cyl->sample_start.mbar)
-			fmt = get_pressure_string(cyl->sample_start, true);
+		if (cyl.start.mbar)
+			return get_pressure_string(cyl.start, true);
+		else if (cyl.sample_start.mbar)
+			return get_pressure_string(cyl.sample_start, true);
 	}
 	if (ret == END_PRESSURE) {
-		if (cyl->end.mbar)
-			fmt = get_pressure_string(cyl->end, true);
-		else if(cyl->sample_end.mbar)
-			fmt = get_pressure_string(cyl->sample_end, true);
+		if (cyl.end.mbar)
+			return get_pressure_string(cyl.end, true);
+		else if (cyl.sample_end.mbar)
+			return get_pressure_string(cyl.sample_end, true);
 	}
-	return fmt;
+	return QString();
 }
 
 QString formatSac(const dive *d)
@@ -77,9 +76,9 @@ QString format_gps_decimal(const dive *d)
 QStringList formatGetCylinder(const dive *d)
 {
 	QStringList getCylinder;
-	for (int i = 0; i < d->cylinders.nr; i++) {
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		if (is_cylinder_used(d, i))
-			getCylinder << get_cylinder(d, i)->type.description;
+			getCylinder << QString::fromStdString(cyl.type.description);
 	}
 	return getCylinder;
 }
@@ -87,9 +86,9 @@ QStringList formatGetCylinder(const dive *d)
 QStringList formatStartPressure(const dive *d)
 {
 	QStringList startPressure;
-	for (int i = 0; i < d->cylinders.nr; i++) {
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		if (is_cylinder_used(d, i))
-			startPressure << getPressures(d, i, START_PRESSURE);
+			startPressure << getPressures(cyl, START_PRESSURE);
 	}
 	return startPressure;
 }
@@ -97,9 +96,9 @@ QStringList formatStartPressure(const dive *d)
 QStringList formatEndPressure(const dive *d)
 {
 	QStringList endPressure;
-	for (int i = 0; i < d->cylinders.nr; i++) {
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		if (is_cylinder_used(d, i))
-			endPressure << getPressures(d, i, END_PRESSURE);
+			endPressure << getPressures(cyl, END_PRESSURE);
 	}
 	return endPressure;
 }
@@ -107,9 +106,9 @@ QStringList formatEndPressure(const dive *d)
 QStringList formatFirstGas(const dive *d)
 {
 	QStringList gas;
-	for (int i = 0; i < d->cylinders.nr; i++) {
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		if (is_cylinder_used(d, i))
-			gas << get_gas_string(get_cylinder(d, i)->gasmix);
+			gas << get_gas_string(cyl.gasmix);
 	}
 	return gas;
 }
@@ -133,20 +132,14 @@ static void addStringToSortedList(QStringList &l, const std::string &s)
 	l.insert(it, qs);
 }
 
-// Safely treat null-strings. Remove once everyhting is converted to std::string
-static std::string c_to_std(const char *s)
-{
-	return s ? std::string(s) : std::string();
-}
-
 QStringList formatFullCylinderList()
 {
 	QStringList cylinders;
 	struct dive *d;
 	int i = 0;
 	for_each_dive (i, d) {
-		for (int j = 0; j < d->cylinders.nr; j++)
-			addStringToSortedList(cylinders, c_to_std(get_cylinder(d, j)->type.description));
+		for (const cylinder_t &cyl: d->cylinders)
+			addStringToSortedList(cylinders, cyl.type.description);
 	}
 
 	for (const auto &ti: tank_info_table)
@@ -155,25 +148,22 @@ QStringList formatFullCylinderList()
 	return cylinders;
 }
 
-static QString formattedCylinder(const struct dive *dive, int idx)
+static QString formattedCylinder(const cylinder_t &cyl)
 {
-	const cylinder_t *cyl = get_cylinder(dive, idx);
-	const char *desc = cyl->type.description;
-	QString fmt = desc ? QString(desc) : gettextFromC::tr("unknown");
-	fmt += ", " + get_volume_string(cyl->type.size, true);
-	fmt += ", " + get_pressure_string(cyl->type.workingpressure, true);
-	fmt += ", " + get_pressure_string(cyl->start, false) + " - " + get_pressure_string(cyl->end, true);
-	fmt += ", " + get_gas_string(cyl->gasmix);
+	const std::string &desc = cyl.type.description;
+	QString fmt = !desc.empty() ? QString::fromStdString(desc) : gettextFromC::tr("unknown");
+	fmt += ", " + get_volume_string(cyl.type.size, true);
+	fmt += ", " + get_pressure_string(cyl.type.workingpressure, true);
+	fmt += ", " + get_pressure_string(cyl.start, false) + " - " + get_pressure_string(cyl.end, true);
+	fmt += ", " + get_gas_string(cyl.gasmix);
 	return fmt;
 }
 
 QStringList formatCylinders(const dive *d)
 {
 	QStringList cylinders;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		QString cyl = formattedCylinder(d, i);
-		cylinders << cyl;
-	}
+	for (const cylinder_t &cyl: d->cylinders)
+		cylinders << formattedCylinder(cyl);
 	return cylinders;
 }
 
@@ -182,14 +172,14 @@ QString formatGas(const dive *d)
 	/*WARNING: here should be the gastlist, returned
 	 * from the get_gas_string function or this is correct?
 	 */
-	QString gas, gases;
-	for (int i = 0; i < d->cylinders.nr; i++) {
+	QString gases;
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
 		if (!is_cylinder_used(d, i))
 			continue;
-		gas = get_cylinder(d, i)->type.description;
+		QString gas = QString::fromStdString(cyl.type.description);
 		if (!gas.isEmpty())
 			gas += QChar(' ');
-		gas += gasname(get_cylinder(d, i)->gasmix);
+		gas += gasname(cyl.gasmix);
 		// if has a description and if such gas is not already present
 		if (!gas.isEmpty() && gases.indexOf(gas) == -1) {
 			if (!gases.isEmpty())
diff --git a/core/uemis.cpp b/core/uemis.cpp
index 33ec3539f..0f65d71f6 100644
--- a/core/uemis.cpp
+++ b/core/uemis.cpp
@@ -335,7 +335,7 @@ void uemis::parse_divelog_binary(std::string_view base64, struct dive *dive)
 	u_sample = (uemis_sample *)(data.data() + i);
 	while ((i <= data.size()) && (data[i] != 0 || data[i + 1] != 0)) {
 		if (u_sample->active_tank != active) {
-			if (u_sample->active_tank >= dive->cylinders.nr) {
+			if (u_sample->active_tank >= static_cast<int>(dive->cylinders.size())) {
 				report_info("got invalid sensor #%d was #%d", u_sample->active_tank, active);
 			} else {
 				active = u_sample->active_tank;
diff --git a/desktop-widgets/profilewidget.cpp b/desktop-widgets/profilewidget.cpp
index 8fcb8f66d..81439ad96 100644
--- a/desktop-widgets/profilewidget.cpp
+++ b/desktop-widgets/profilewidget.cpp
@@ -298,7 +298,7 @@ void ProfileWidget::cylindersChanged(struct dive *changed, int pos)
 	// If we're editing the current dive we have to update the
 	// cylinders of the edited dive.
 	if (editedDive) {
-		copy_cylinders(&d->cylinders, &editedDive.get()->cylinders);
+		editedDive.get()->cylinders = d->cylinders;
 		// TODO: Holy moly that function sends too many signals. Fix it!
 		DivePlannerPointsModel::instance()->loadFromDive(editedDive.get(), dc);
 	}
diff --git a/desktop-widgets/simplewidgets.cpp b/desktop-widgets/simplewidgets.cpp
index 748820d31..00cd24a8d 100644
--- a/desktop-widgets/simplewidgets.cpp
+++ b/desktop-widgets/simplewidgets.cpp
@@ -23,6 +23,7 @@
 #include "profile-widget/profilewidget2.h"
 #include "commands/command.h"
 #include "core/metadata.h"
+#include "core/range.h"
 #include "core/tag.h"
 
 void RenumberDialog::buttonClicked(QAbstractButton *button)
@@ -348,11 +349,10 @@ void DiveComponentSelection::buttonClicked(QAbstractButton *button)
 			text << "\n";
 		}
 		if (what->cylinders) {
-			int cyl;
 			text << tr("Cylinders:\n");
-			for (cyl = 0; cyl < current_dive->cylinders.nr; cyl++) {
-				if (is_cylinder_used(current_dive, cyl))
-					text << get_cylinder(current_dive, cyl)->type.description << " " << gasname(get_cylinder(current_dive, cyl)->gasmix) << "\n";
+			for (auto [idx, cyl]: enumerated_range(current_dive->cylinders)) {
+				if (is_cylinder_used(current_dive, idx))
+					text << QString::fromStdString(cyl.type.description) << " " << gasname(cyl.gasmix) << "\n";
 			}
 		}
 		if (what->weights) {
diff --git a/desktop-widgets/tab-widgets/TabDiveInformation.cpp b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
index 73394a4aa..f08594fe0 100644
--- a/desktop-widgets/tab-widgets/TabDiveInformation.cpp
+++ b/desktop-widgets/tab-widgets/TabDiveInformation.cpp
@@ -126,14 +126,14 @@ void TabDiveInformation::updateProfile()
 
 	std::vector<volume_t> gases = get_gas_used(currentDive);
 	QString volumes;
-	std::vector<int> mean(currentDive->cylinders.nr), duration(currentDive->cylinders.nr);
+	std::vector<int> mean(currentDive->cylinders.size()), duration(currentDive->cylinders.size());
 	struct divecomputer *currentdc = parent.getCurrentDC();
-	if (currentdc && currentDive->cylinders.nr >= 0)
+	if (currentdc && !currentDive->cylinders.empty())
 		per_cylinder_mean_depth(currentDive, currentdc, mean.data(), duration.data());
 	volume_t sac;
 	QString gaslist, SACs, separator;
 
-	for (int i = 0; i < currentDive->cylinders.nr; i++) {
+	for (size_t i = 0; i < currentDive->cylinders.size(); i++) {
 		if (!is_cylinder_used(currentDive, i))
 			continue;
 		gaslist.append(separator); volumes.append(separator); SACs.append(separator);
@@ -154,7 +154,7 @@ void TabDiveInformation::updateProfile()
 	ui->diveTimeText->setText(get_dive_duration_string(currentDive->duration.seconds, tr("h"), tr("min"), tr("sec"),
 			" ", currentDive->dcs[0].divemode == FREEDIVE));
 
-	ui->sacText->setText(currentDive->cylinders.nr > 0 && mean[0] && currentDive->dcs[0].divemode != CCR ? std::move(SACs) : QString());
+	ui->sacText->setText(!currentDive->cylinders.empty() && mean[0] && currentDive->dcs[0].divemode != CCR ? std::move(SACs) : QString());
 
 	if (currentDive->surface_pressure.mbar == 0) {
 		ui->atmPressVal->clear();			// If no atm pressure for dive then clear text box
diff --git a/desktop-widgets/templatelayout.cpp b/desktop-widgets/templatelayout.cpp
index fb58f0629..47ebfa8e2 100644
--- a/desktop-widgets/templatelayout.cpp
+++ b/desktop-widgets/templatelayout.cpp
@@ -303,9 +303,9 @@ static int findEnd(const QList<token> &tokenList, int from, int to, token_t star
 static std::vector<const cylinder_t *> cylinderList(const dive *d)
 {
 	std::vector<const cylinder_t *> res;
-	res.reserve(d->cylinders.nr);
-	for (int i = 0; i < d->cylinders.nr; ++i)
-		res.push_back(&d->cylinders.cylinders[i]);
+	res.reserve(d->cylinders.size());
+	for (auto &cyl: d->cylinders)
+		res.push_back(&cyl);
 	return res;
 }
 
@@ -481,7 +481,7 @@ QVariant TemplateLayout::getValue(QString list, QString property, const State &s
 			return QVariant();
 		const cylinder_t *cylinder = *state.currentCylinderObject;
 		if (property == "description") {
-			return cylinder->type.description;
+			return QString::fromStdString(cylinder->type.description);
 		} else if (property == "size") {
 			return get_volume_string(cylinder->type.size, true);
 		} else if (property == "workingPressure") {
diff --git a/mobile-widgets/qmlmanager.cpp b/mobile-widgets/qmlmanager.cpp
index 40c5417de..9cf600738 100644
--- a/mobile-widgets/qmlmanager.cpp
+++ b/mobile-widgets/qmlmanager.cpp
@@ -1295,7 +1295,7 @@ void QMLManager::commitChanges(QString diveId, QString number, QString date, QSt
 					break;
 				}
 			}
-			get_or_create_cylinder(d, j)->type.description = copy_qstring(usedCylinder[k]);
+			get_or_create_cylinder(d, j)->type.description = usedCylinder[k].toStdString();
 			get_cylinder(d, j)->type.size.mliter = size;
 			get_cylinder(d, j)->type.workingpressure.mbar = wp;
 			k++;
diff --git a/profile-widget/diveprofileitem.cpp b/profile-widget/diveprofileitem.cpp
index 4b75bda82..a4573c8b1 100644
--- a/profile-widget/diveprofileitem.cpp
+++ b/profile-widget/diveprofileitem.cpp
@@ -602,7 +602,10 @@ void DiveGasPressureItem::replot(const dive *d, int fromIn, int toIn, bool in_pl
 
 	bool showDescriptions = false;
 	for (int cyl = 0; cyl < pInfo.nr_cylinders; cyl++) {
-		showDescriptions = showDescriptions || same_gasmix_cylinder(get_cylinder(d, cyl), cyl, d, true) != -1;
+		const cylinder_t *c = get_cylinder(d, cyl);
+		if (!c)
+			continue;
+		showDescriptions = showDescriptions || (c && same_gasmix_cylinder(*c, cyl, d, true) != -1);
 		if (act_segments[cyl].polygon.empty())
 			continue;
 		act_segments[cyl].cyl = cyl;
@@ -655,7 +658,7 @@ void DiveGasPressureItem::plotGasValue(double mbar, double sec, const cylinder_t
 	QString gas = get_gas_string(cylinder->gasmix);
 	QString label;
 	if (showDescription)
-		label = QStringLiteral("(%1) %2").arg(cylinder->type.description, gas);
+		label = QStringLiteral("(%1) %2").arg(QString::fromStdString(cylinder->type.description), gas);
 	else
 		label = gas;
 	auto text = std::make_unique<DiveTextItem>(dpr, 1.0, align, this);
diff --git a/profile-widget/profilewidget2.cpp b/profile-widget/profilewidget2.cpp
index 0ff940d84..ce235a27b 100644
--- a/profile-widget/profilewidget2.cpp
+++ b/profile-widget/profilewidget2.cpp
@@ -502,13 +502,11 @@ struct int ProfileWidget2::getEntryFromPos(QPointF pos)
 #ifndef SUBSURFACE_MOBILE
 /// Prints cylinder information for display.
 /// eg : "Cyl 1 (AL80 EAN32)"
-static QString printCylinderDescription(int i, const cylinder_t *cylinder)
+static QString printCylinderDescription(int i, const cylinder_t &cylinder)
 {
 	QString label = gettextFromC::tr("Cyl") + QString(" %1").arg(i+1);
-	if( cylinder != NULL ) {
-		QString mix = get_gas_string(cylinder->gasmix);
-		label += QString(" (%2 %3)").arg(cylinder->type.description).arg(mix);
-	}
+	QString mix = get_gas_string(cylinder.gasmix);
+	label += QString(" (%2 %3)").arg(QString::fromStdString(cylinder.type.description)).arg(mix);
 	return label;
 }
 
@@ -562,18 +560,16 @@ void ProfileWidget2::contextMenuEvent(QContextMenuEvent *event)
 	if (d && item && item->ev.is_gaschange()) {
 		int eventTime = item->ev.time.seconds;
 		QMenu *gasChange = m.addMenu(tr("Edit Gas Change"));
-		for (int i = 0; i < d->cylinders.nr; i++) {
-			const cylinder_t *cylinder = get_cylinder(d, i);
-			QString label = printCylinderDescription(i, cylinder);
-			gasChange->addAction(label, [this, i, eventTime] { addGasSwitch(i, eventTime); });
+		for (auto [i, cyl]: enumerated_range(d->cylinders)) {
+			QString label = printCylinderDescription(i, cyl);
+			gasChange->addAction(label, [this, idx = i, eventTime] { addGasSwitch(idx, eventTime); });
 		}
-	} else if (d && d->cylinders.nr > 1) {
+	} else if (d && d->cylinders.size() > 1) {
 		// if we have more than one gas, offer to switch to another one
 		QMenu *gasChange = m.addMenu(tr("Add gas change"));
-		for (int i = 0; i < d->cylinders.nr; i++) {
-			const cylinder_t *cylinder = get_cylinder(d, i);
-			QString label = printCylinderDescription(i, cylinder);
-			gasChange->addAction(label, [this, i, seconds] { addGasSwitch(i, seconds); });
+		for (auto [i, cyl]: enumerated_range(d->cylinders)) {
+			QString label = printCylinderDescription(i, cyl);
+			gasChange->addAction(label, [this, idx = i, seconds] { addGasSwitch(idx, seconds); });
 		}
 	}
 	m.addAction(tr("Add setpoint change"), [this, seconds]() { ProfileWidget2::addSetpointChange(seconds); });
@@ -763,7 +759,7 @@ void ProfileWidget2::splitDive(int seconds)
 
 void ProfileWidget2::addGasSwitch(int tank, int seconds)
 {
-	if (!d || tank < 0 || tank >= d->cylinders.nr)
+	if (!d || tank < 0 || static_cast<size_t>(tank) >= d->cylinders.size())
 		return;
 
 	Command::addGasSwitch(mutable_dive(), dc, seconds, tank);
@@ -923,7 +919,7 @@ void ProfileWidget2::repositionDiveHandlers()
 		QLineF line(p1, p2);
 		QPointF pos = line.pointAt(0.5);
 		gases[i]->setPos(pos);
-		if (datapoint.cylinderid >= 0 && datapoint.cylinderid < d->cylinders.nr)
+		if (datapoint.cylinderid >= 0 && datapoint.cylinderid < static_cast<int>(d->cylinders.size()))
 			gases[i]->setText(get_gas_string(get_cylinder(d, datapoint.cylinderid)->gasmix));
 		else
 			gases[i]->setText(QString());
diff --git a/profile-widget/tankitem.cpp b/profile-widget/tankitem.cpp
index 5df474e83..e92a5b0d1 100644
--- a/profile-widget/tankitem.cpp
+++ b/profile-widget/tankitem.cpp
@@ -76,7 +76,7 @@ void TankItem::setData(const struct dive *d, const struct divecomputer *dc, int
 		return;
 
 	// Bail if there are no cylinders
-	if (d->cylinders.nr <= 0)
+	if (d->cylinders.empty())
 		return;
 
 	// start with the first gasmix and at the start of the plotted range
diff --git a/qt-models/cylindermodel.cpp b/qt-models/cylindermodel.cpp
index 203d48ae7..4e87feef0 100644
--- a/qt-models/cylindermodel.cpp
+++ b/qt-models/cylindermodel.cpp
@@ -6,6 +6,7 @@
 #include "core/color.h"
 #include "qt-models/diveplannermodel.h"
 #include "core/gettextfromc.h"
+#include "core/range.h"
 #include "core/sample.h"
 #include "core/selection.h"
 #include "core/subsurface-qt/divelistnotifier.h"
@@ -140,7 +141,7 @@ int CylindersModel::calcNumRows() const
 	if (!d)
 		return 0;
 	if (inPlanner || prefs.include_unused_tanks)
-		return d->cylinders.nr;
+		return static_cast<int>(d->cylinders.size());
 	return first_hidden_cylinder(d);
 }
 
@@ -192,7 +193,7 @@ QVariant CylindersModel::data(const QModelIndex &index, int role) const
 	case Qt::EditRole:
 		switch (index.column()) {
 		case TYPE:
-			return QString(cyl->type.description);
+			return QString::fromStdString(cyl->type.description);
 		case SIZE:
 			if (cyl->type.size.mliter)
 				return get_cylinder_string(cyl);
@@ -326,10 +327,9 @@ bool CylindersModel::setData(const QModelIndex &index, const QVariant &value, in
 
 		switch (index.column()) {
 		case TYPE: {
-			QString type = value.toString();
-			if (!same_string(qPrintable(type), tempCyl.type.description)) {
-				free((void *)tempCyl.type.description);
-				tempCyl.type.description = strdup(qPrintable(type));
+			std::string type = value.toString().toStdString();
+			if (type != tempCyl.type.description) {
+				tempCyl.type.description = type;
 				dataChanged(index, index);
 			}
 			return true;
@@ -361,8 +361,6 @@ bool CylindersModel::setData(const QModelIndex &index, const QVariant &value, in
 	QString vString = value.toString();
 	bool changed = vString != data(index, role).toString();
 
-	std::string newType; // If we allocate a new type string, this makes sure that it is freed at the end of the function
-
 	// First, we make a shallow copy of the old cylinder. Then we modify the fields inside that copy.
 	// At the end, we either place an EditCylinder undo command (EquipmentTab) or copy the cylinder back (planner).
 	// Yes, this is not ideal, but the pragmatic thing to do for now.
@@ -374,8 +372,7 @@ bool CylindersModel::setData(const QModelIndex &index, const QVariant &value, in
 	Command::EditCylinderType type = Command::EditCylinderType::TYPE;
 	switch (index.column()) {
 	case TYPE:
-		newType = qPrintable(vString);
-		cyl.type.description = newType.c_str();
+		cyl.type.description = vString.toStdString();
 		type = Command::EditCylinderType::TYPE;
 		break;
 	case SIZE:
@@ -473,10 +470,7 @@ bool CylindersModel::setData(const QModelIndex &index, const QVariant &value, in
 
 	if (inPlanner) {
 		// In the planner - simply overwrite the cylinder in the dive with the modified cylinder.
-		// We have only made a shallow copy, therefore copy the new cylinder first.
-		cylinder_t copy = clone_cylinder(cyl);
-		std::swap(copy, *get_cylinder(d, row));
-		free_cylinder(copy);
+		*get_cylinder(d, row) = cyl;
 		dataChanged(index, index);
 	} else {
 		// On the EquipmentTab - place an editCylinder command.
@@ -496,10 +490,10 @@ void CylindersModel::add()
 {
 	if (!d)
 		return;
-	int row = d->cylinders.nr;
+	int row = static_cast<int>(d->cylinders.size());
 	cylinder_t cyl = create_new_manual_cylinder(d);
 	beginInsertRows(QModelIndex(), row, row);
-	add_cylinder(&d->cylinders, row, cyl);
+	add_cylinder(&d->cylinders, row, std::move(cyl));
 	++numRows;
 	endInsertRows();
 	emit dataChanged(createIndex(row, 0), createIndex(row, COLUMNS - 1));
@@ -552,7 +546,7 @@ void CylindersModel::remove(QModelIndex index)
 	--numRows;
 	endRemoveRows();
 
-	std::vector<int> mapping = get_cylinder_map_for_remove(d->cylinders.nr + 1, index.row());
+	std::vector<int> mapping = get_cylinder_map_for_remove(static_cast<int>(d->cylinders.size() + 1), index.row());
 	cylinder_renumber(d, mapping.data());
 	DivePlannerPointsModel::instance()->cylinderRenumber(mapping.data());
 }
@@ -612,21 +606,18 @@ void CylindersModel::updateNumRows()
 // Only invoked from planner.
 void CylindersModel::moveAtFirst(int cylid)
 {
-	if (!d || cylid <= 0 || cylid >= d->cylinders.nr)
+	if (!d || cylid <= 0 || cylid >= static_cast<int>(d->cylinders.size()))
 		return;
 	cylinder_t temp_cyl;
 
 	beginMoveRows(QModelIndex(), cylid, cylid, QModelIndex(), 0);
-	memmove(&temp_cyl, get_cylinder(d, cylid), sizeof(temp_cyl));
-	for (int i = cylid - 1; i >= 0; i--)
-		memmove(get_cylinder(d, i + 1), get_cylinder(d, i), sizeof(temp_cyl));
-	memmove(get_cylinder(d, 0), &temp_cyl, sizeof(temp_cyl));
+	move_in_range(d->cylinders, cylid, cylid + 1, 0);
 
 	// Create a mapping of cylinder indices:
 	// 1) Fill mapping[0]..mapping[cyl] with 0..index
 	// 2) Set mapping[cyl] to 0
 	// 3) Fill mapping[cyl+1]..mapping[end] with cyl..
-	std::vector<int> mapping(d->cylinders.nr);
+	std::vector<int> mapping(d->cylinders.size());
 	std::iota(mapping.begin(), mapping.begin() + cylid, 1);
 	mapping[cylid] = 0;
 	std::iota(mapping.begin() + (cylid + 1), mapping.end(), cylid);
@@ -644,12 +635,11 @@ void CylindersModel::updateDecoDepths(pressure_t olddecopo2)
 
 	pressure_t decopo2;
 	decopo2.mbar = prefs.decopo2;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(d, i);
+	for (auto &cyl: d->cylinders) {
 		/* If the gas's deco MOD matches the old pO2, it will have been automatically calculated and should be updated.
 		 * If they don't match, we should leave the user entered depth as it is */
-		if (cyl->depth.mm == gas_mod(cyl->gasmix, olddecopo2, d, M_OR_FT(3, 10)).mm) {
-			cyl->depth = gas_mod(cyl->gasmix, decopo2, d, M_OR_FT(3, 10));
+		if (cyl.depth.mm == gas_mod(cyl.gasmix, olddecopo2, d, M_OR_FT(3, 10)).mm) {
+			cyl.depth = gas_mod(cyl.gasmix, decopo2, d, M_OR_FT(3, 10));
 		}
 	}
 	emit dataChanged(createIndex(0, 0), createIndex(numRows - 1, COLUMNS - 1));
@@ -671,23 +661,22 @@ bool CylindersModel::updateBestMixes()
 
 	// Check if any of the cylinders are best mixes, update if needed
 	bool gasUpdated = false;
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(d, i);
-		if (cyl->bestmix_o2) {
-			cyl->gasmix.o2 = best_o2(d->maxdepth, d, inPlanner);
+	for (auto &cyl: d->cylinders) {
+		if (cyl.bestmix_o2) {
+			cyl.gasmix.o2 = best_o2(d->maxdepth, d, inPlanner);
 			// fO2 + fHe must not be greater than 1
-			if (get_o2(cyl->gasmix) + get_he(cyl->gasmix) > 1000)
-				cyl->gasmix.he.permille = 1000 - get_o2(cyl->gasmix);
+			if (get_o2(cyl.gasmix) + get_he(cyl.gasmix) > 1000)
+				cyl.gasmix.he.permille = 1000 - get_o2(cyl.gasmix);
 			pressure_t modpO2;
 			modpO2.mbar = prefs.decopo2;
-			cyl->depth = gas_mod(cyl->gasmix, modpO2, d, M_OR_FT(3, 10));
+			cyl.depth = gas_mod(cyl.gasmix, modpO2, d, M_OR_FT(3, 10));
 			gasUpdated = true;
 		}
-		if (cyl->bestmix_he) {
-			cyl->gasmix.he = best_he(d->maxdepth, d, prefs.o2narcotic, cyl->gasmix.o2);
+		if (cyl.bestmix_he) {
+			cyl.gasmix.he = best_he(d->maxdepth, d, prefs.o2narcotic, cyl.gasmix.o2);
 			// fO2 + fHe must not be greater than 1
-			if (get_o2(cyl->gasmix) + get_he(cyl->gasmix) > 1000)
-				cyl->gasmix.o2.permille = 1000 - get_he(cyl->gasmix);
+			if (get_o2(cyl.gasmix) + get_he(cyl.gasmix) > 1000)
+				cyl.gasmix.o2.permille = 1000 - get_he(cyl.gasmix);
 			gasUpdated = true;
 		}
 	}
@@ -727,7 +716,7 @@ void CylindersModel::initTempCyl(int row)
 		return;
 
 	tempRow = row;
-	tempCyl = clone_cylinder(*cyl);
+	tempCyl = *cyl;
 
 	dataChanged(index(row, TYPE), index(row, USE));
 }
@@ -738,7 +727,7 @@ void CylindersModel::clearTempCyl()
 		return;
 	int oldRow = tempRow;
 	tempRow = -1;
-	free_cylinder(tempCyl);
+	tempCyl = cylinder_t();
 	dataChanged(index(oldRow, TYPE), index(oldRow, USE));
 }
 
@@ -752,7 +741,7 @@ void CylindersModel::commitTempCyl(int row)
 	if (!cyl)
 		return;
 	// Only submit a command if the type changed
-	if (!same_string(cyl->type.description, tempCyl.type.description) || gettextFromC::tr(cyl->type.description) != QString(tempCyl.type.description)) {
+	if (cyl->type.description != tempCyl.type.description || gettextFromC::tr(cyl->type.description.c_str()) != QString::fromStdString(tempCyl.type.description)) {
 		if (inPlanner) {
 			std::swap(*cyl, tempCyl);
 		} else {
@@ -760,6 +749,6 @@ void CylindersModel::commitTempCyl(int row)
 			emit divesEdited(count);
 		}
 	}
-	free_cylinder(tempCyl);
+	tempCyl = cylinder_t();
 	tempRow = -1;
 }
diff --git a/qt-models/diveplannermodel.cpp b/qt-models/diveplannermodel.cpp
index 234b09fc3..69996cc4f 100644
--- a/qt-models/diveplannermodel.cpp
+++ b/qt-models/diveplannermodel.cpp
@@ -195,13 +195,13 @@ void DivePlannerPointsModel::loadFromDive(dive *dIn, int dcNrIn)
 // setup the cylinder widget accordingly
 void DivePlannerPointsModel::setupCylinders()
 {
-	clear_cylinder_table(&d->cylinders);
+	d->cylinders.clear();
 	if (mode == PLAN && current_dive) {
 		// take the displayed cylinders from the selected dive as starting point
 		copy_used_cylinders(current_dive, d, !prefs.include_unused_tanks);
 		reset_cylinders(d, true);
 
-		if (d->cylinders.nr > 0) {
+		if (!d->cylinders.empty()) {
 			cylinders.updateDive(d, dcNr);
 			return;		// We have at least one cylinder
 		}
@@ -281,13 +281,14 @@ QVariant DivePlannerPointsModel::data(const QModelIndex &index, int role) const
 		case GAS:
 			/* Check if we have the same gasmix two or more times
 			 * If yes return more verbose string */
-			int same_gas = same_gasmix_cylinder(get_cylinder(d, p.cylinderid), p.cylinderid, d, true);
+			const cylinder_t &cyl = d->cylinders[p.cylinderid];
+			int same_gas = same_gasmix_cylinder(cyl, p.cylinderid, d, true);
 			if (same_gas == -1)
-				return get_gas_string(get_cylinder(d, p.cylinderid)->gasmix);
+				return get_gas_string(cyl.gasmix);
 			else
-				return get_gas_string(get_cylinder(d, p.cylinderid)->gasmix) +
+				return get_gas_string(cyl.gasmix) +
 					QString(" (%1 %2 ").arg(tr("cyl.")).arg(p.cylinderid + 1) +
-						get_cylinder(d, p.cylinderid)->type.description + ")";
+						QString::fromStdString(cyl.type.description) + ")";
 		}
 	} else if (role == Qt::DecorationRole) {
 		switch (index.column()) {
@@ -602,6 +603,7 @@ void DivePlannerPointsModel::setAscratestopsDisplay(int rate)
 	qPrefDivePlanner::set_ascratestops(lrint(rate * unit_factor()));
 	emitDataChanged();
 }
+
 int DivePlannerPointsModel::ascratestopsDisplay() const
 {
 	return lrint((float)prefs.ascratestops / unit_factor());
@@ -1028,11 +1030,9 @@ void DivePlannerPointsModel::createTemporaryPlan()
 	// Get the user-input and calculate the dive info
 	free_dps(&diveplan);
 
-	for (int i = 0; i < d->cylinders.nr; i++) {
-		cylinder_t *cyl = get_cylinder(d, i);
-		if (cyl->depth.mm && cyl->cylinder_use == OC_GAS) {
-			plan_add_segment(&diveplan, 0, cyl->depth.mm, i, 0, false, OC);
-		}
+	for (auto [i, cyl]: enumerated_range(d->cylinders)) {
+		if (cyl.depth.mm && cyl.cylinder_use == OC_GAS)
+			plan_add_segment(&diveplan, 0, cyl.depth.mm, i, 0, false, OC);
 	}
 
 	int lastIndex = -1;
diff --git a/qt-models/divesummarymodel.cpp b/qt-models/divesummarymodel.cpp
index a3345a396..43cb8d6ce 100644
--- a/qt-models/divesummarymodel.cpp
+++ b/qt-models/divesummarymodel.cpp
@@ -151,12 +151,9 @@ static void calculateDive(struct dive *dive, Stats &stats)
 	}
 
 	// EAN dive ?
-	for (int j = 0; j < dive->cylinders.nr; ++j) {
-		if (get_cylinder(dive, j)->gasmix.o2.permille > 210) {
-			stats.divesEAN++;
-			break;
-		}
-	}
+	if (std::any_of(dive->cylinders.begin(), dive->cylinders.end(), [] (auto &cyl)
+			{ return cyl.gasmix.o2.permille > 210; }))
+		stats.divesEAN++;
 }
 
 // Returns a (first_dive, last_dive) pair
diff --git a/qt-models/divetripmodel.cpp b/qt-models/divetripmodel.cpp
index d2d858ca1..80b298458 100644
--- a/qt-models/divetripmodel.cpp
+++ b/qt-models/divetripmodel.cpp
@@ -336,7 +336,7 @@ QVariant DiveTripModelBase::diveData(const struct dive *d, int column, int role)
 		case SUIT:
 			return QString(d->suit);
 		case CYLINDER:
-			return d->cylinders.nr > 0 ? QString(get_cylinder(d, 0)->type.description) : QString();
+			return !d->cylinders.empty() ? QString::fromStdString(d->cylinders[0].type.description) : QString();
 		case SAC:
 			return displaySac(d, prefs.units.show_units_table);
 		case OTU:
@@ -1721,6 +1721,11 @@ static int strCmp(const char *s1, const char *s2)
 	return QString::localeAwareCompare(QString(s1), QString(s2)); // TODO: avoid copy
 }
 
+static int strCmp(const std::string &s1, const std::string &s2)
+{
+	return QString::localeAwareCompare(QString::fromStdString(s1), QString::fromStdString(s2)); // TODO: avoid copy
+}
+
 bool DiveTripModelList::lessThan(const QModelIndex &i1, const QModelIndex &i2) const
 {
 	// We assume that i1.column() == i2.column().
@@ -1750,9 +1755,9 @@ bool DiveTripModelList::lessThan(const QModelIndex &i1, const QModelIndex &i2) c
 	case SUIT:
 		return lessThanHelper(strCmp(d1->suit, d2->suit), row_diff);
 	case CYLINDER:
-		if (d1->cylinders.nr > 0 && d2->cylinders.nr > 0)
-			return lessThanHelper(strCmp(get_cylinder(d1, 0)->type.description, get_cylinder(d2, 0)->type.description), row_diff);
-		return d1->cylinders.nr - d2->cylinders.nr < 0;
+		if (!d1->cylinders.empty() && !d2->cylinders.empty())
+			return lessThanHelper(strCmp(d1->cylinders[0].type.description, d2->cylinders[0].type.description), row_diff);
+		return d1->cylinders.size() < d2->cylinders.size();
 	case GAS:
 		return lessThanHelper(nitrox_sort_value(d1) - nitrox_sort_value(d2), row_diff);
 	case SAC:
@@ -1764,19 +1769,19 @@ bool DiveTripModelList::lessThan(const QModelIndex &i1, const QModelIndex &i2) c
 	case TAGS: {
 		std::string s1 = taglist_get_tagstring(d1->tag_list);
 		std::string s2 = taglist_get_tagstring(d2->tag_list);
-		int diff = strCmp(s1.c_str(), s2.c_str());
+		int diff = strCmp(s1, s2);
 		return lessThanHelper(diff, row_diff);
 	}
 	case PHOTOS:
 		return lessThanHelper(countPhotos(d1) - countPhotos(d2), row_diff);
 	case COUNTRY:
-		return lessThanHelper(strCmp(get_dive_country(d1).c_str(), get_dive_country(d2).c_str()), row_diff);
+		return lessThanHelper(strCmp(get_dive_country(d1), get_dive_country(d2)), row_diff);
 	case BUDDIES:
 		return lessThanHelper(strCmp(d1->buddy, d2->buddy), row_diff);
 	case DIVEGUIDE:
 		return lessThanHelper(strCmp(d1->diveguide, d2->diveguide), row_diff);
 	case LOCATION:
-		return lessThanHelper(strCmp(get_dive_location(d1).c_str(), get_dive_location(d2).c_str()), row_diff);
+		return lessThanHelper(strCmp(get_dive_location(d1), get_dive_location(d2)), row_diff);
 	case NOTES:
 		return lessThanHelper(strCmp(d1->notes, d2->notes), row_diff);
 	case DIVEMODE:
diff --git a/smtk-import/smartrak.cpp b/smtk-import/smartrak.cpp
index 5aeafee25..391001573 100644
--- a/smtk-import/smartrak.cpp
+++ b/smtk-import/smartrak.cpp
@@ -449,7 +449,7 @@ static void smtk_build_tank_info(MdbHandle *mdb, cylinder_t *tank, char *idx)
 
 	for (i = 1; i <= atoi(idx); i++)
 		table.fetch_row();
-	tank->type.description = copy_string(table.get_data(1));
+	tank->type.description = table.get_data(1);
 	tank->type.size.mliter = lrint(strtod(table.get_data(2), NULL) * 1000);
 	tank->type.workingpressure.mbar = lrint(strtod(table.get_data(4), NULL) * 1000);
 }
@@ -472,9 +472,9 @@ static bool is_same_cylinder(cylinder_t *cyl_a, cylinder_t *cyl_b)
 	if (!(abs(cyl_a->end.mbar - cyl_b->end.mbar) <= 100))
 		return false;
 	// different names (none of them null)
-	if (!same_string(cyl_a->type.description, "---") &&
-	    !same_string(cyl_b->type.description, "---") &&
-	    !same_string(cyl_a->type.description, cyl_b->type.description))
+	if (cyl_a->type.description != "---" &&
+	    cyl_b->type.description != "---" &&
+	    cyl_a->type.description != cyl_b->type.description)
 		return false;
 	// Cylinders are most probably the same
 	return true;
@@ -495,9 +495,8 @@ static void merge_cylinder_type(cylinder_type_t *src, cylinder_type_t *dst)
 		dst->size.mliter = src->size.mliter;
 	if (!dst->workingpressure.mbar)
 		dst->workingpressure.mbar = src->workingpressure.mbar;
-	if (!dst->description || same_string(dst->description, "---")) {
-		dst->description = src->description;
-		src->description = NULL;
+	if (dst->description.empty() || dst->description == "---") {
+		dst->description = std::move(src->description);
 	}
 }
 
@@ -532,7 +531,7 @@ static void smtk_clean_cylinders(struct dive *d)
 
 	cyl = base + tanks - 1;
 	while (cyl != base) {
-		if (same_string(cyl->type.description, "---") && cyl->start.mbar == 0 && cyl->end.mbar == 0)
+		if (cyl->type.description == "---" && cyl->start.mbar == 0 && cyl->end.mbar == 0)
 			remove_cylinder(d, i);
 		else
 			if (is_same_cylinder(cyl, cyl - 1)) {
diff --git a/stats/statsvariables.cpp b/stats/statsvariables.cpp
index c7a770838..33caf3f44 100644
--- a/stats/statsvariables.cpp
+++ b/stats/statsvariables.cpp
@@ -1553,9 +1553,9 @@ struct GasTypeBinner : public MultiBinner<GasTypeBinner, GasTypeBin> {
 	}
 	std::vector<gas_bin_t> to_bin_values(const dive *d) const {
 		std::vector<gas_bin_t> res;
-		res.reserve(d->cylinders.nr);
-		for (int i = 0; i < d->cylinders.nr; ++i) {
-			struct gasmix mix = d->cylinders.cylinders[i].gasmix;
+		res.reserve(d->cylinders.size());
+		for (auto &cyl: d->cylinders) {
+			struct gasmix mix = cyl.gasmix;
 			if (gasmix_is_invalid(mix))
 				continue;
 			// Add dive to each bin only once.
@@ -1591,9 +1591,9 @@ struct GasTypeGeneralBinner : public MultiBinner<GasTypeGeneralBinner, IntBin> {
 	}
 	std::vector<int> to_bin_values(const dive *d) const {
 		std::vector<int> res;
-		res.reserve(d->cylinders.nr);
-		for (int i = 0; i < d->cylinders.nr; ++i) {
-			struct gasmix mix = d->cylinders.cylinders[i].gasmix;
+		res.reserve(d->cylinders.size());
+		for (auto &cyl: d->cylinders) {
+			struct gasmix mix = cyl.gasmix;
 			if (gasmix_is_invalid(mix))
 				continue;
 			res.push_back(gasmix_to_type(mix));
@@ -1619,9 +1619,9 @@ struct GasTypeVariable : public StatsVariableTemplate<StatsVariable::Type::Discr
 	QString diveCategories(const dive *d) const override {
 		QString res;
 		std::vector<gasmix> mixes;	// List multiple cylinders only once
-		mixes.reserve(d->cylinders.nr);
-		for (int i = 0; i < d->cylinders.nr; ++i) {
-			struct gasmix mix = d->cylinders.cylinders[i].gasmix;
+		mixes.reserve(d->cylinders.size());
+		for (auto &cyl: d->cylinders) {
+			struct gasmix mix = cyl.gasmix;
 			if (gasmix_is_invalid(mix))
 				continue;
 			if (std::find_if(mixes.begin(), mixes.end(),
@@ -1648,7 +1648,7 @@ struct GasTypeVariable : public StatsVariableTemplate<StatsVariable::Type::Discr
 //  - max_he: get cylinder with maximum he content, otherwise with maximum o2 content
 static int get_gas_content(const struct dive *d, bool he, bool max_he)
 {
-	if (d->cylinders.nr <= 0)
+	if (d->cylinders.empty())
 		return invalid_value<int>();
 	// If sorting be He, the second sort criterion is O2 descending, because
 	// we are interested in the "bottom gas": highest He and lowest O2.
@@ -1657,7 +1657,7 @@ static int get_gas_content(const struct dive *d, bool he, bool max_he)
 					 std::make_tuple(get_he(c2.gasmix), -get_o2(c2.gasmix)); }
 			   : [] (const cylinder_t &c1, const cylinder_t &c2)
 				{ return get_o2(c1.gasmix) < get_o2(c2.gasmix); };
-	auto it = std::max_element(d->cylinders.cylinders, d->cylinders.cylinders + d->cylinders.nr, comp);
+	auto it = std::max_element(d->cylinders.begin(), d->cylinders.end(), comp);
 	return he ? get_he(it->gasmix) : get_o2(it->gasmix);
 }
 
@@ -1798,9 +1798,9 @@ struct WeightsystemVariable : public StatsVariableTemplate<StatsVariable::Type::
 static std::vector<QString> cylinder_types(const dive *d)
 {
 	std::vector<QString> res;
-	res.reserve(d->cylinders.nr);
-	for (int i = 0; i < d->cylinders.nr; ++i)
-		add_to_vector_unique(res, QString(d->cylinders.cylinders[i].type.description).trimmed());
+	res.reserve(d->cylinders.size());
+	for (auto &cyl: d->cylinders)
+		add_to_vector_unique(res, QString::fromStdString(cyl.type.description).trimmed());
 	return res;
 }