[sanitizer_common] Disable sanitizer_redefine_builtins on Apple platforms

[DanBlackwell]

This currently generates many linker warnings of this form, due to defining mem(cpy|move|set) in every object file:

ld: warning: '.../build/projects/compiler-rt/lib/interception/CMakeFiles/RTInterception.ios.dir/interception_linux.cpp.o' has malformed LC_DYSYMTAB, expected 6 undefined symbols to start at index 1, found 3 undefined symbols starting at index 1

In order for this to actually replace these symbols on mach-o, they would need a leading underscore, e.g. .set _memcpy, ___sanitizer_internal_memcpy. However doing so does not fix the warnings, and furthermore it ends up replacing REAL(memcpy) calls with __sanitizer_internal_memcpy in places such as __asan::Allocator::Reallocate. There is no way on Apple platforms to recreate the intended behaviour, so let's just disable this on them to reduce warning noise.

rdar://123771479

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Dan Blackwell (DanBlackwell)

Changes

This currently generates many linker warnings of this form, due to defining mem(cpy|move|set) in every object file:

ld: warning: '.../build/projects/compiler-rt/lib/interception/CMakeFiles/RTInterception.ios.dir/interception_linux.cpp.o' has malformed LC_DYSYMTAB, expected 6 undefined symbols to start at index 1, found 3 undefined symbols starting at index 1

In order for this to actually replace these symbols on mach-o, they would need a leading underscore, e.g. .set _memcpy, ___sanitizer_internal_memcpy. However doing so does not fix the warnings, and furthermore it ends up replacing REAL(memcpy) calls with __sanitizer_internal_memcpy in places such as __asan::Allocator::Reallocate. There is no way on Apple platforms to recreate the intended behaviour, so let's just disable this on them to reduce warning noise.

rdar://123771479

---

Full diff: https://github.com/llvm/llvm-project/pull/153381.diff

1 Files Affected:

• (modified) compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h (+1-1)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h b/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h
index bda0f04687693..7d88911176577 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_redefine_builtins.h
@@ -15,7 +15,7 @@
 #    define SANITIZER_REDEFINE_BUILTINS_H
 
 // The asm hack only works with GCC and Clang.
-#    if !defined(_WIN32) && !defined(_AIX)
+#    if !defined(_WIN32) && !defined(_AIX) && !defined(__APPLE__)
 
 asm(R"(
     .set memcpy, __sanitizer_internal_memcpy

[DanBlackwell]

@thurstond If I make the sanitizer_redefine_builtins work as intended, it replaces REAL(memcpy) calls such as [this] with the internal implementation. Perhaps it's worth checking whether the same happens on Linux, and whether this is intended behaviour?