[libcxx-commits] [libcxx] [libc++] Fix bogus integer sanitizer warnings in hash helpers (PR #146715)

[Louis Dionne via libcxx-commits]

================
@@ -132,11 +132,12 @@ struct __murmur2_or_cityhash<_Size, 64> {
   static const _Size __k2 = 0x9ae16a3b2f90404fULL;
   static const _Size __k3 = 0xc949d7c7509e6557ULL;
 
-  _LIBCPP_HIDE_FROM_ABI static _Size __rotate(_Size __val, int __shift) {
+  _LIBCPP_HIDE_FROM_ABI static _Size _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK __rotate(_Size __val, int __shift) {
----------------
ldionne wrote:

I would suggest adding a comment explaining the reason. In fact, we could even do this:

```c++
#define _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK(reason) __attribute__((__no_sanitize__("integer")))
```

and ignore the reason. That way, people are forced to write:

```c++
_LIBCPP_HIDE_FROM_ABI static _Size _LIBCPP_DISABLE_UBSAN_INTEGER_CHECK("why is this here?")
__rotate(_Size __val, int __shift)
```

https://github.com/llvm/llvm-project/pull/146715