[libcxx-commits] [libcxx] [ASan][libc++] Turn on ASan annotations for short strings (PR #79536)

[Louis Dionne via libcxx-commits]

ldionne wrote:

@nico I am not certain whether you are arguing for the feature being enabled by default, or being disabled by default but opt-in. I think it's the latter but it's not 100% clear to me.

IMO, (2) is a bug in the Blocks runtime and #96269 will work around that issue until we fix the Blocks runtime. (3) is indeed a problem, but I think the real answer here is that we must begin shipping a sanitized version of libc++ and have the clang driver select the right version based on `-fsanitize=<foo>`. Even the long string markup suffers from this problem although it might be less of an actual issue in practice.

TLDR, I am still leaning towards keeping this enabled by default except on Apple where it is currently badly broken due to the blocks runtime. If it turns out that (3) is a big problem and is biting users quite a bit, perhaps we should revisit this decision and keep it disabled until we actually ship a different dylib based on `-fsanitize=foo`.

https://github.com/llvm/llvm-project/pull/79536