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fix M159 - crash at end of prayer

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Fix the crash caused by division by zero (attempt to compute rn2(0))
when deciding prayer boon for a character whose Luck went negative during
the course of the prayer.  <email deleted> triggered it
by killing a shopkeeper with the ongoing damage from a scroll of stinking
cloud; his non-chaotic character was branded a murderer and lost two points
of Luck after the prayer was already in progress.  (Prayers fail when Luck
is already negative, so the code to pick a boon expects non-negative values;
the fact that is always adds at least +2 leads to me to suspect that someone
already realized that luck timeout on Friday 13th could result in Luck of -1
at the end of a successful prayer--that value doesn't trigger this crash.)
This commit is contained in:
nethack.rankin
2005-09-02 06:00:44 +00:00
parent bbc825f9d9
commit 8ce7216a0c
2 changed files with 17 additions and 2 deletions
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18
src/pray.c
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@@ -1,4 +1,4 @@
/* SCCS Id: @(#)pray.c 3.5 2005/06/24 */
/* SCCS Id: @(#)pray.c 3.5 2005/08/31 */
/* Copyright (c) Benson I. Margulies, Mike Stephenson, Steve Linhart, 1989. */
/* NetHack may be freely redistributed. See license for details. */
@@ -844,8 +844,22 @@ pleased(g_align)
/* if hero was in trouble, but got better, no special favor */
if (p_trouble == 0) pat_on_head = 1;
} else {
int action = rn1(Luck + (on_altar() ? 3 + on_shrine() : 2), 1);
int action, prayer_luck;
/* Negative luck is normally impossible here (can_pray() forces
prayer failure in that situation), but it's possible for
Luck to drop during the period of prayer occupation and
become negative by the time we get here. [Reported case
was lawful character whose stinking cloud caused a delayed
killing of a peaceful human, triggering the "murderer"
penalty while successful prayer was in progress. It could
also happen due to inconvenient timing on Friday 13th, but
the magnitude there (-1) isn't big enough to cause trouble.]
We don't bother remembering start-of-prayer luck, just make
sure it's at least -1 so that Luck+2 is big enough to avoid
a divide by zero crash when generating a random number. */
prayer_luck = max(Luck, -1); /* => (prayer_luck + 2 > 0) */
action = rn1(prayer_luck + (on_altar() ? 3 + on_shrine() : 2), 1);
if (!on_altar()) action = min(action, 3);
if (u.ualign.record < STRIDENT)
action = (u.ualign.record > 0 || !rnl(2)) ? 1 : 0;