[libcxx-commits] [libcxx] [ASan][libc++] Update string ASan annotations to Zero-overhead (PR #76165)

[Louis Dionne via libcxx-commits]

================
@@ -1490,6 +1490,16 @@ __sanitizer_verify_double_ended_contiguous_container(const void*, const void*, c
 #    define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 #  endif
 
+// ASan related macros
+// _LIBCPP_IF_ASAN is used to removed ASan related code, whenever compiled without ASan.
+#ifndef _LIBCPP_IF_ASAN
+#  ifndef _LIBCPP_HAS_NO_ASAN
+#    define _LIBCPP_IF_ASAN() if _LIBCPP_CONSTEXPR (true)
+#  else
+#    define _LIBCPP_IF_ASAN() if _LIBCPP_CONSTEXPR (false)
+#  endif
+#endif
----------------
ldionne wrote:

```suggestion
#  ifndef _LIBCPP_HAS_NO_ASAN
#    define _LIBCPP_IF_ASAN() if _LIBCPP_CONSTEXPR (true)
#  else
#    define _LIBCPP_IF_ASAN() if _LIBCPP_CONSTEXPR (false)
#  endif
```

I don't think we need to check for `#ifndef _LIBCPP_IF_ASAN` -- we only do that when we allow macros to be redefined by users.

https://github.com/llvm/llvm-project/pull/76165