core: convert sample.c to C++ and add default constructor

This changes default behavior when creating a sample struct
in C++ code: it is now initialized to default values. If this
ever turns out to be a performance problem, we can either add
additional constructors or use special functions that do
not initialize memory, such as make_unique_for_overwrite.

This removes non-standard (respectively >C++20) constructs,
namely designated initializers.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

Subsurface-mobile.pro

@@ -66,7 +66,7 @@ SOURCES += subsurface-mobile-main.cpp \
 	core/parse.c \
 	core/picture.c \
 	core/pictureobj.cpp \
-	core/sample.c \
+	core/sample.cpp \
 	core/import-suunto.c \
 	core/import-shearwater.c \
 	core/import-seac.c \

core/CMakeLists.txt

@@ -153,7 +153,7 @@ set(SUBSURFACE_CORE_LIB_SRCS
 	qthelper.cpp
 	qthelper.h
 	range.h
-	sample.c
+	sample.cpp
 	sample.h
 	save-git.c
 	save-html.c

core/dive.cpp

@@ -1337,7 +1337,7 @@ static void merge_one_sample(const struct sample *sample, int time, struct divec
 		 * a minute apart, and shallower than 5m
 		 */
 		if (time > last_time + 60 && last_depth < 5000) {
-			struct sample surface = { 0 };
+			struct sample surface;
 
 			/* Init a few values from prev sample to avoid useless info in XML */
 			surface.bearing.degrees = prev->bearing.degrees;
@@ -1388,7 +1388,7 @@ static void merge_samples(struct divecomputer *res,
 	for (;;) {
 		int j;
 		int at, bt;
-		struct sample sample = { .ndl{ -1 } , .bearing{ -1 } };
+		struct sample sample;
 
 		if (!res)
 			return;

core/sample.cpp

@@ -2,6 +2,28 @@
 
 #include "sample.h"
 
+sample::sample() :
+	time({ 0 }),
+	stoptime({ 0 }),
+	ndl({ -1 }),
+	tts({ 0 }),
+	rbt({ 0 }),
+	depth({ 0 }),
+	stopdepth({ 0 }),
+	temperature({ 0 }),
+	pressure { { 0 }, { 0 } },
+	setpoint({ 0 }),
+	o2sensor { { 0 }, { 0 }, { 0 }, { 0 }, { 0 }, { 0 } },
+	bearing({ -1 }),
+	sensor { 0, 0 },
+	cns(0),
+	heartbeat(0),
+	sac({ 0 }),
+	in_deco(false),
+	manually_entered(false)
+{
+}
+
 /*
  * Adding a cylinder pressure sample field is not quite as trivial as it
  * perhaps should be.
@@ -15,7 +37,7 @@
  * from the previous sample, so the indices are pre-populated (but the
  * pressures obviously are not)
  */
-void add_sample_pressure(struct sample *sample, int sensor, int mbar)
+extern "C" void add_sample_pressure(struct sample *sample, int sensor, int mbar)
 {
 	int idx;
 
@@ -42,4 +64,3 @@ void add_sample_pressure(struct sample *sample, int sensor, int mbar)
 	/* We do not have enough slots for the pressure samples. */
 	/* Should we warn the user about dropping pressure data? */
 }
-

core/sample.h

@@ -33,6 +33,9 @@ struct sample                         // BASE TYPE BYTES  UNITS    RANGE
 	bool in_deco;                     // bool       1    y/n      y/n                  this sample is part of deco
 	bool manually_entered;            // bool       1    y/n      y/n                  this sample was entered by the user,
 					  //                                               not calculated when planning a dive
+#ifdef __cplusplus
+	sample();			  // Default constructor
+#endif
 };	                                  // Total size of structure: 63 bytes, excluding padding at end
 
 extern void add_sample_pressure(struct sample *sample, int sensor, int mbar);