Updates:
Status: Done
Comment #11 on issue 137 by
jz...@google.com: WebP source does not compile cleanly with full warnings on.
https://bugs.chromium.org/p/webp/issues/detail?id=137#c11-Wconversion was never really a goal, but we've added much more warning coverage over the years. We're clear with clang, gcc and visual studio as well as running under sanitizers (undefined, integer, tsan, asan, msan, cfi). The most recent conversion warnings we cleared were with clang 7's integer sanitizer (-fsanitize=implicit-integer-truncation). Those were of a similar sort to -Wconversion, but many remain with that flag.
I'm going to mark this bug as closed as we don't have any plans to address those.