profile.c: fix a bug in calculate_gas_information_new()

In a test case loading dives/test35.xml results in a infinite(-like)
loop (Note: possibly requires the partial pressure plots enabled).

calculate_gas_information_new() has an 'if' branch to
update the cylinderindex to a dive's diluent_cylinder_index,
but it does not consider that said index can be set previously
to -1.

This results in a random neighbour memory assigned as
&dive->cylinder[-1].gasmix and passed to fill_pressures(..).

Following the calculations in the function the He gas,
can receive a bad value (e.g. for the test case in the
E+6 ranges).

Said value is then used in DivePlotDataModel()::pheMax()
(defined by MAX_PPGAS_FUNC()) resulting in one of the loops
(the 3rd one) in DiveCartesianAxis::updateTicks() to
loop indefinitely.

Fixes #759

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/profile.c b/profile.c
index d3c5ef857..82d4b653d 100644
--- a/profile.c
+++ b/profile.c
@@ -900,7 +900,7 @@ static void calculate_gas_information_new(struct dive *dive, struct plot_info *p
 		amb_pressure = depth_to_mbar(entry->depth, dive) / 1000.0;
 
 		// For CCR dives use the diluent gas composition for calculating partial gas pressures:
-		if ((dive->dc.dctype == CCR) && (cylinderindex == dive->oxygen_cylinder_index))
+		if (dive->dc.dctype == CCR && cylinderindex == dive->oxygen_cylinder_index && dive->diluent_cylinder_index != -1)
 			cylinderindex = dive->diluent_cylinder_index;
 
 		fill_pressures(&entry->pressures, amb_pressure, &dive->cylinder[cylinderindex].gasmix, entry->pressures.o2, dive->dc.dctype, entry->sac);