Planner: don't return static data in fake_dc()

fake_dc() used to return a statically allocated dc with statically
allocated samples. This is of course a questionable practice in
the light of multi-threading / resource ownership. Once these
problems were recognized, the parameter "alloc" was added. If set
to true, the function would still return a statically allocated
dc, but heap-allocated samples, which could then be copied in
a different dc.

All in all an ownership nightmare and a recipie for disaster.
The returned static dc was only used as a pointer to the samples
anyway. There are four callers of fake_dc() and they all have access
to a dc-structure without samples. Therefore, change the semantics
of fake_dc() to fill out the passed in dc. If the caller does
not care about the samples, it can simply reset the sample number
to zero after work.

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

7 files changed, 39 insertions, 40 deletions

diff --git a/core/device.c b/core/device.c
index d5e723765..c9036304a 100644
--- a/core/device.c
+++ b/core/device.c
@@ -109,33 +109,29 @@ static void fill_samples_no_avg(struct sample *s, int max_d, int max_t, double s
 	}
 }
 
-struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc)
+void fake_dc(struct divecomputer *dc)
 {
-	static struct sample fake_samples[6];
-	static struct divecomputer fakedc;
-	struct sample *fake = fake_samples;
+	alloc_samples(dc, 6);
+	struct sample *fake = dc->sample;
 	int i;
 
-	fakedc = (*dc);
-	if (alloc)
-		fake = malloc(sizeof(fake_samples));
-
-	fakedc.sample = fake;
-	fakedc.samples = 6;
+	dc->samples = 6;
 
 	/* The dive has no samples, so create a few fake ones */
 	int max_t = dc->duration.seconds;
 	int max_d = dc->maxdepth.mm;
 	int avg_d = dc->meandepth.mm;
 
-	memset(fake, 0, sizeof(fake_samples));
+	memset(fake, 0, 6 * sizeof(struct sample));
 	fake[5].time.seconds = max_t;
 	for (i = 0; i < 6; i++) {
-		fake_samples[i].bearing.degrees = -1;
-		fake_samples[i].ndl.seconds = -1;
+		fake[i].bearing.degrees = -1;
+		fake[i].ndl.seconds = -1;
+	}
+	if (!max_t || !max_d) {
+		dc->samples = 0;
+		return;
 	}
-	if (!max_t || !max_d)
-		return &fakedc;
 
 	/*
 	 * We want to fake the profile so that the average
@@ -149,10 +145,10 @@ struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc)
 		 * the user supplied data */
 		fill_samples_no_avg(fake, max_d, max_t, MAX(2.0 * max_d / max_t, 5000.0 / 60));
 		if (fake[3].time.seconds == 0) { // just a 4 point profile
-			fakedc.samples = 4;
+			dc->samples = 4;
 			fake[3].time.seconds = max_t;
 		}
-		return &fakedc;
+		return;
 	}
 	if (avg_d < max_d / 10 || avg_d >= max_d) {
 		avg_d = (max_d + 10000) / 3;
@@ -167,7 +163,7 @@ struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc)
 	 * rate (5 meters per minute) and d_frac (1/3).
 	 */
 	if (fill_samples(fake, max_d, avg_d, max_t, 5000.0 / 60, 0.33))
-		return &fakedc;
+		return;
 
 	/*
 	 * Ok, assume that didn't work because we cannot make the
@@ -175,7 +171,7 @@ struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc)
 	 * followed by a much shallower region
 	 */
 	if (fill_samples(fake, max_d, avg_d, max_t, 10000.0 / 60, 0.10))
-		return &fakedc;
+		return;
 
 	/*
 	 * Uhhuh. That didn't work. We'd need to find a good combination that
@@ -183,10 +179,9 @@ struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc)
 	 * slopes.
 	 */
 	if (fill_samples(fake, max_d, avg_d, max_t, 10000.0, 0.01))
-		return &fakedc;
+		return;
 
 	/* Even that didn't work? Give up, there's something wrong */
-	return &fakedc;
 }
 
 static void match_id(void *_dc, const char *model, uint32_t deviceid,
diff --git a/core/device.h b/core/device.h
index df069a1d5..14a80144c 100644
--- a/core/device.h
+++ b/core/device.h
@@ -7,7 +7,7 @@
 extern "C" {
 #endif
 
-extern struct divecomputer *fake_dc(struct divecomputer *dc, bool alloc);
+extern void fake_dc(struct divecomputer *dc);
 extern void set_dc_deviceid(struct divecomputer *dc, unsigned int deviceid);
 extern void create_device_node(const char *model, uint32_t deviceid, const char *serial, const char *firmware, const char *nickname);
 extern void call_for_each_dc(void *f, void (*callback)(void *, const char *, uint32_t,
diff --git a/core/dive.c b/core/dive.c
index 811c0270c..3d7c0f486 100644
--- a/core/dive.c
+++ b/core/dive.c
@@ -714,22 +714,26 @@ void copy_samples(struct divecomputer *s, struct divecomputer *d)
 		memcpy(d->sample, s->sample, nr * sizeof(struct sample));
 }
 
+/* make room for num samples; if not enough space is available, the sample
+ * array is reallocated and the existing samples are copied. */
+void alloc_samples(struct divecomputer *dc, int num)
+{
+	if (num > dc->alloc_samples) {
+		dc->alloc_samples = (dc->alloc_samples * 3) / 2 + 10;
+		dc->sample = realloc(dc->sample, dc->alloc_samples * sizeof(struct sample));
+		if (!dc->sample)
+			dc->samples = dc->alloc_samples = 0;
+	}
+}
+
 struct sample *prepare_sample(struct divecomputer *dc)
 {
 	if (dc) {
 		int nr = dc->samples;
-		int alloc_samples = dc->alloc_samples;
 		struct sample *sample;
-		if (nr >= alloc_samples) {
-			struct sample *newsamples;
-
-			alloc_samples = (alloc_samples * 3) / 2 + 10;
-			newsamples = realloc(dc->sample, alloc_samples * sizeof(struct sample));
-			if (!newsamples)
-				return NULL;
-			dc->alloc_samples = alloc_samples;
-			dc->sample = newsamples;
-		}
+		alloc_samples(dc, nr + 1);
+		if (!dc->sample)
+			return NULL;
 		sample = dc->sample + nr;
 		memset(sample, 0, sizeof(*sample));
 
@@ -922,7 +926,7 @@ void per_cylinder_mean_depth(struct dive *dive, struct divecomputer *dc, int *me
 		return;
 	}
 	if (!dc->samples)
-		dc = fake_dc(dc, false);
+		fake_dc(dc);
 	struct event *ev = get_next_event(dc->events, "gaschange");
 	for (i = 0; i < dc->samples; i++) {
 		struct sample *sample = dc->sample + i;
diff --git a/core/dive.h b/core/dive.h
index 795203545..854ec82ba 100644
--- a/core/dive.h
+++ b/core/dive.h
@@ -792,6 +792,7 @@ extern struct dive *clone_dive(struct dive *s);
 
 extern void clear_table(struct dive_table *table);
 
+extern void alloc_samples(struct divecomputer *dc, int num);
 extern struct sample *prepare_sample(struct divecomputer *dc);
 extern void finish_sample(struct divecomputer *dc);
 extern void add_sample_pressure(struct sample *sample, int sensor, int mbar);
diff --git a/mobile-widgets/qmlmanager.cpp b/mobile-widgets/qmlmanager.cpp
index bd8ea29a3..a7345363c 100644
--- a/mobile-widgets/qmlmanager.cpp
+++ b/mobile-widgets/qmlmanager.cpp
@@ -1089,9 +1089,9 @@ void QMLManager::commitChanges(QString diveId, QString date, QString location, Q
 			// so we have depth > 0, a manually added dive and no samples
 			// let's create an actual profile so the desktop version can work it
 			// first clear out the mean depth (or the fake_dc() function tries
-			// to be too clever
+			// to be too clever)
 			d->meandepth.mm = d->dc.meandepth.mm = 0;
-			d->dc = *fake_dc(&d->dc, true);
+			fake_dc(&d->dc);
 		}
 		fixup_dive(d);
 		DiveListModel::instance()->updateDive(modelIdx, d);
diff --git a/profile-widget/profilewidget2.cpp b/profile-widget/profilewidget2.cpp
index 78bd294d4..fa0e98cea 100644
--- a/profile-widget/profilewidget2.cpp
+++ b/profile-widget/profilewidget2.cpp
@@ -592,9 +592,8 @@ void ProfileWidget2::plotDive(struct dive *d, bool force)
 	// data that we have
 	struct divecomputer *currentdc = select_dc(&displayed_dive);
 	Q_ASSERT(currentdc);
-	if (!currentdc || !currentdc->samples) {
-		currentdc = fake_dc(currentdc, false);
-	}
+	if (!currentdc || !currentdc->samples)
+		fake_dc(currentdc);
 
 	bool setpointflag = (currentdc->divemode == CCR) && prefs.pp_graphs.po2 && current_dive;
 	bool sensorflag = setpointflag && prefs.show_ccr_sensors;
diff --git a/qt-models/diveplannermodel.cpp b/qt-models/diveplannermodel.cpp
index 0745c362d..d65fa771f 100644
--- a/qt-models/diveplannermodel.cpp
+++ b/qt-models/diveplannermodel.cpp
@@ -99,7 +99,7 @@ void DivePlannerPointsModel::loadFromDive(dive *d)
 	if (dc->samples)
 		hasMarkedSamples = dc->sample[0].manually_entered;
 	else
-		dc = fake_dc(dc, true);
+		fake_dc(dc);
 
 	// if this dive has more than 100 samples (so it is probably a logged dive),
 	// average samples so we end up with a total of 100 samples.