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TOLTECS: Fix unaligned access causing SIGBUS in Screen::addAnimatedSprite() #3974


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@dwatteau dwatteau commented Jun 6, 2022

The demo would SIGBUS in Screen::addAnimatedSprite() when playing it on OpenBSD/loongson, which has a mips64el CPU with strict-alignment constraints. This is the same setup as for my older PR #2241.

Changing the FROM_LE_16() calls there to READ_LE_UINT16() calls fixes the issue. Looking a bit at common/endian.h, it appears that only the latter properly deals with unaligned memory accesses. Commit 30e3a81 was a similar change.

This possibly fixes the game on other strict-alignment ports such as Dreamcast, PSP or some old ARM devices.

On x86-64 and Apple M1, screen.o remains identical before and after this change, as expected. I think it's safe to cherry-pick this for the 2.6.0 release, but you're the judges :)

Use READ_LE_UINT16 instead of FROM_LE_16 to avoid unaligned memory
access, as seen on OpenBSD/loongson (mips64el) where it would SIGBUS
when trying to play the demo.
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@bluegr bluegr commented Jun 7, 2022

Nice! Thanks for spotting this

@bluegr bluegr merged commit 980b693 into scummvm:master Jun 7, 2022
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@dwatteau dwatteau deleted the fix/toltecs-addAnimatedSprite-unaligned-access branch Jun 7, 2022
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