Clean up signedness confusion in dive.c

This started out as cleaning up warnings - but it actually turned into a
matter of semantics and correctness. Which lead to changes in .h files
which will have a ton of ripple effects.

A lot more of this to come.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

3 files changed, 17 insertions, 14 deletions

diff --git a/subsurface-core/dive.c b/subsurface-core/dive.c
index 083767582..47b3e1f06 100644
--- a/subsurface-core/dive.c
+++ b/subsurface-core/dive.c
@@ -58,7 +58,7 @@ int event_gasmix_redundant(struct event *ev)
 		he == ev->gas.mix.he.permille;
 }
 
-struct event *add_event(struct divecomputer *dc, int time, int type, int flags, int value, const char *name)
+struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name)
 {
 	int gas_index = -1;
 	struct event *ev, **p;
@@ -738,7 +738,8 @@ void per_cylinder_mean_depth(struct dive *dive, struct divecomputer *dc, int *me
 {
 	int i;
 	int depthtime[MAX_CYLINDERS] = { 0, };
-	int lasttime = 0, lastdepth = 0;
+	uint32_t lasttime = 0;
+	int lastdepth = 0;
 	int idx = 0;
 
 	for (i = 0; i < MAX_CYLINDERS; i++)
@@ -765,7 +766,7 @@ void per_cylinder_mean_depth(struct dive *dive, struct divecomputer *dc, int *me
 		dc = fake_dc(dc, false);
 	for (i = 0; i < dc->samples; i++) {
 		struct sample *sample = dc->sample + i;
-		int time = sample->time.seconds;
+		uint32_t time = sample->time.seconds;
 		int depth = sample->depth.mm;
 
 		/* Make sure to move the event past 'lasttime' */
@@ -2619,7 +2620,8 @@ static struct divetag *taglist_add_divetag(struct tag_entry **tag_list, struct d
 
 struct divetag *taglist_add_tag(struct tag_entry **tag_list, const char *tag)
 {
-	int i = 0, is_default_tag = 0;
+	size_t i = 0;
+	int is_default_tag = 0;
 	struct divetag *ret_tag, *new_tag;
 	const char *translation;
 	new_tag = malloc(sizeof(struct divetag));
@@ -2675,7 +2677,7 @@ static void taglist_merge(struct tag_entry **dst, struct tag_entry *src1, struct
 
 void taglist_init_global()
 {
-	int i;
+	size_t i;
 
 	for (i = 0; i < sizeof(default_tags) / sizeof(char *); i++)
 		taglist_add_tag(&g_tag_list, default_tags[i]);
@@ -2920,7 +2922,8 @@ static void force_fixup_dive(struct dive *d)
  */
 static int split_dive_at(struct dive *dive, int a, int b)
 {
-	int i, t, nr;
+	int i, nr;
+	uint32_t t;
 	struct dive *d1, *d2;
 	struct divecomputer *dc1, *dc2;
 	struct event *event, **evp;
@@ -3249,7 +3252,7 @@ void set_informational_units(char *units)
 	}
 }
 
-void average_max_depth(struct diveplan *dive, int *avg_depth, int *max_depth)
+void average_max_depth(struct diveplan *dive, unsigned int *avg_depth, unsigned int *max_depth)
 {
 	int integral = 0;
 	int last_time = 0;
@@ -3415,7 +3418,7 @@ void make_first_dc()
 }
 
 /* always acts on the current dive */
-int count_divecomputers(void)
+unsigned int count_divecomputers(void)
 {
 	int ret = 1;
 	struct divecomputer *dc = current_dive->dc.next;
@@ -3455,7 +3458,7 @@ void delete_current_divecomputer(void)
 
 /* helper function to make it easier to work with our structures
  * we don't interpolate here, just use the value from the last sample up to that time */
-int get_depth_at_time(struct divecomputer *dc, int time)
+int get_depth_at_time(struct divecomputer *dc, unsigned int time)
 {
 	int depth = 0;
 	if (dc && dc->sample)
diff --git a/subsurface-core/dive.h b/subsurface-core/dive.h
index f8970b237..f84d45c24 100644
--- a/subsurface-core/dive.h
+++ b/subsurface-core/dive.h
@@ -387,7 +387,7 @@ extern timestamp_t picture_get_timestamp(char *filename);
 extern void dive_set_geodata_from_picture(struct dive *d, struct picture *pic);
 
 extern int explicit_first_cylinder(struct dive *dive, struct divecomputer *dc);
-extern int get_depth_at_time(struct divecomputer *dc, int time);
+extern int get_depth_at_time(struct divecomputer *dc, unsigned int time);
 
 static inline int get_surface_pressure_in_mbar(const struct dive *dive, bool non_null)
 {
@@ -567,7 +567,7 @@ static inline struct divecomputer *get_dive_dc(struct dive *dive, int nr)
 extern timestamp_t dive_endtime(const struct dive *dive);
 
 extern void make_first_dc(void);
-extern int count_divecomputers(void);
+extern unsigned int count_divecomputers(void);
 extern void delete_current_divecomputer(void);
 
 /*
@@ -737,7 +737,7 @@ extern void copy_samples(struct divecomputer *s, struct divecomputer *d);
 extern bool is_cylinder_used(struct dive *dive, int idx);
 extern void fill_default_cylinder(cylinder_t *cyl);
 extern void add_gas_switch_event(struct dive *dive, struct divecomputer *dc, int time, int idx);
-extern struct event *add_event(struct divecomputer *dc, int time, int type, int flags, int value, const char *name);
+extern struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const char *name);
 extern void remove_event(struct event *event);
 extern void update_event_name(struct dive *d, struct event* event, char *name);
 extern void add_extra_data(struct divecomputer *dc, const char *key, const char *value);
@@ -892,7 +892,7 @@ extern depth_t string_to_depth(const char *str);
 extern pressure_t string_to_pressure(const char *str);
 extern volume_t string_to_volume(const char *str, pressure_t workp);
 extern fraction_t string_to_fraction(const char *str);
-extern void average_max_depth(struct diveplan *dive, int *avg_depth, int *max_depth);
+extern void average_max_depth(struct diveplan *dive, unsigned int *avg_depth, unsigned int *max_depth);
 
 #include "pref.h"
 
diff --git a/subsurface-core/units.h b/subsurface-core/units.h
index 9ad4b7282..029bb64fa 100644
--- a/subsurface-core/units.h
+++ b/subsurface-core/units.h
@@ -99,7 +99,7 @@ typedef struct
 
 typedef struct
 {
-	int32_t mkelvin; // up to 1750 degrees K
+	uint32_t mkelvin; // up to 1750 degrees K (temperatures in K are always positive)
 } temperature_t;
 
 typedef struct