[all-commits] [llvm/llvm-project] c68a9d: [ASan][libc++] String annotations optimizations fi...

[Tacet via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c68a9d25e99a096f6862fc4b57dd380a21245d31
      https://github.com/llvm/llvm-project/commit/c68a9d25e99a096f6862fc4b57dd380a21245d31
  Author: Tacet <advenam.tacet at trailofbits.com>
  Date:   2024-01-08 (Mon, 08 Jan 2024)

  Changed paths:
    M libcxx/include/string

  Log Message:
  -----------
  [ASan][libc++] String annotations optimizations fix with lambda (#76200)

This commit addresses optimization and instrumentation challenges
encountered within comma constructors.
1) _LIBCPP_STRING_INTERNAL_MEMORY_ACCESS does not work in comma
constructors.
2) Code inside comma constructors is not always correctly optimized.
Problematic code examples:
- `: __r_(((__str.__is_long() ? 0 : (__str.__annotate_delete(), 0)),
std::move(__str.__r_))) {`
- `: __r_(__r_([&](){ if(!__s.__is_long()) __s.__annotate_delete();
return std::move(__s.__r_);}())) {`

However, lambda with argument seems to be correctly optimized. The patch employs this.

Use of lambda based on an idea from @ldionne.