When media-libs/libsdl-1.2.15-r9 is compiled with the altivec use-flag set on ppc64le, color corruption is observed in wesnoth (and presumably other libsdl2 consumers). When it is compiled with -altivec, the color corruption goes away.
Steps to Reproduce:
1. Compile media-libs/libsdl2 with altivec set on ppc64le
2. Run Wesnoth
3. Observe the corrupted colors
Corrupted colors observed in wesnoth
No corrupted colors
No corrupted colors observed on same platform with only media-libs/libsdl2 recompiled without altivec.
Ok, I was pulling wrong information when I posted the report... It should have been media-libs/libsdl2-2.0.10 listed, not the libsdl1 version. My apologies.
Being somewhat obscure hardware, I can't easily test this myself and it is almost certainly an upstream bug anyway. Could you please report it there and link it here?
Would it be practical to package.use.mask altivec for ppc64le as a temporary workaround?
Reported upstream https://bugzilla.libsdl.org/show_bug.cgi?id=4834