Warn about non-monotonous plot data and prevent infinite loop

The data are supposed to be sorted with monotonous time stamp. And while
the actual bug that causes this needs to be identified and fixed, this is
at least a stop gap measure that shows the issue and prevents Subsurface
from hanging.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/profile.c b/profile.c
index 158517e2d..b676dc5b0 100644
--- a/profile.c
+++ b/profile.c
@@ -849,6 +849,12 @@ void calculate_deco_information(struct dive *dive, struct divecomputer *dc, stru
 									 (prefs.gflow - prefs.gfhigh) +
 								 prefs.gfhigh) *
 					(100.0 - AMB_PERCENTAGE) / 100.0 + AMB_PERCENTAGE;
+		if (t0 > t1) {
+			fprintf(stderr, "non-monotonous dive stamps %d %d\n", t0, t1);
+			int xchg = t1;
+			t1 = t0;
+			t0 = xchg;
+		}
 		if (t0 != t1 && t1 - t0 < time_stepsize)
 			time_stepsize = t1 - t0;
 		for (j = t0 + time_stepsize; j <= t1; j += time_stepsize) {