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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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1
doc/fixes34.4
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@@ -140,6 +140,7 @@ weaken "farming" strategy
don't suppress corpse if you kill your own steed
fix typo in tourist quest leader's greeting
fix grammar for graveyard sounds when polymorphed
avoid divide by zero crash if Luck drops below -1 while a prayer is in progress
Platform- and/or Interface-Specific Fixes

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;