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Core: don't return invalid cylinders from explicit_first_cylinder()

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For reasons which I don't yet understand, when plotting a dive
whose first cylinder is not cylinder 0 and then plotting a dive
with only one cylinder, it can happen that for the latter
explicit_first_cylinder() returns an erroneous value.

This is due to the way in which we copy the dive to be plotted
to displayed_dive.

For now, make sure that no invalid cylinder is returned to avoid
crashes. This will have to be changed anyway, since this is very
fundamentally not thread-safe and inefficient.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
This commit is contained in:
Berthold Stoeger 2019-12-23 22:02:10 +01:00 • committed by bstoeger
parent 763dbf256a
commit 62adc24d15
1 changed files with 6 additions and 4 deletions
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10
core/dive.c
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@ -865,17 +865,19 @@ static int same_rounded_pressure(pressure_t a, pressure_t b)
/* Some dive computers (Cobalt) don't start the dive with cylinder 0 but explicitly /* Some dive computers (Cobalt) don't start the dive with cylinder 0 but explicitly
* tell us what the first gas is with a gas change event in the first sample. * tell us what the first gas is with a gas change event in the first sample.
* Sneakily we'll use a return value of 0 (or FALSE) when there is no explicit * Sneakily we'll use a return value of 0 (or FALSE) when there is no explicit
* first cylinder - in which case cylinder 0 is indeed the first cylinder */ * first cylinder - in which case cylinder 0 is indeed the first cylinder.
* We likewise return 0 if the event concerns a cylinder that doesn't exist. */
int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *dc) int explicit_first_cylinder(const struct dive *dive, const struct divecomputer *dc)
{ {
int res = 0;
if (dc) { if (dc) {
const struct event *ev = get_next_event(dc->events, "gaschange"); const struct event *ev = get_next_event(dc->events, "gaschange");
if (ev && ((dc->sample && ev->time.seconds == dc->sample[0].time.seconds) || ev->time.seconds <= 1)) if (ev && ((dc->sample && ev->time.seconds == dc->sample[0].time.seconds) || ev->time.seconds <= 1))
return get_cylinder_index(dive, ev); res = get_cylinder_index(dive, ev);
else if (dc->divemode == CCR) else if (dc->divemode == CCR)
return MAX(get_cylinder_idx_by_use(dive, DILUENT), 0); res = MAX(get_cylinder_idx_by_use(dive, DILUENT), 0);
} }
return 0; return res < dive->cylinders.nr ? res : 0;
} }
/* this gets called when the dive mode has changed (so OC vs. CC) /* this gets called when the dive mode has changed (so OC vs. CC)