ref: 40e74e7f69074141d70b93fd904679e3b32d96d7
parent: a7765f722a266d9c35613150f8526b64678ae695
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Sun Aug 16 18:12:11 EDT 2015
games/doom: fix array offsets for respawn angle (thanks qu7uux) mthing->angle is a signed short, and if ANG45 * mthing->angle/45 < 0, the result of the right shift is sign extended. afaik, an being 16bit in the dos version of doom, you'd endup with a negative array offset, which would just access values from adjacent arrays (finetangent[] for finecosine[], and finecosine[] for finesine[]), and it would result in a misplaced teleport fog in some circumstances (fog is not in front of the player on respawn, hence "silent teleport"). so, this fix is bug incompatible, but this only affects live multiplay. to test: % hget http://doomedsda.us/dm/ahfx7_2.zip | unzip -sv extracting AHFX7_2.TXT extracting AHFX7_2.LMP % mv AHFX7_2.LMP ahfx7_2.lmp % games/doom -playdemo ahfx7_2 [...] doom 10553: suicide: sys: trap: fault read addr=0x400429e10 pc=0x205b45
--- a/sys/src/games/doom/g_game.c
+++ b/sys/src/games/doom/g_game.c
@@ -860,7 +860,7 @@
// spawn a teleport fog
ss = R_PointInSubsector (x,y);
- an = ( ANG45 * (mthing->angle/45) ) >> ANGLETOFINESHIFT;
+ an = ( ANG45 * ((unsigned)mthing->angle/45) ) >> ANGLETOFINESHIFT;
mo = P_SpawnMobj (x+20*finecosine[an], y+20*finesine[an]
, ss->sector->floorheight
--
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