[compiler-rt] rtsan: Support free_sized and free_aligned_sized from C23 (PR #145085)

[Justin King via llvm-commits]

================
@@ -869,6 +869,48 @@ INTERCEPTOR(void, free, void *ptr) {
   return REAL(free)(ptr);
 }
 
+#if SANITIZER_INTERCEPT_FREE_SIZED
+INTERCEPTOR(void, free_sized, void *ptr, SIZE_T size) {
+  if (DlsymAlloc::PointerIsMine(ptr))
+    return DlsymAlloc::Free(ptr);
+
+  // According to the C and C++ standard, freeing a nullptr is guaranteed to be
+  // a no-op (and thus real-time safe). This can be confirmed for looking at
+  // __libc_free in the glibc source.
+  if (ptr != nullptr)
+    __rtsan_notify_intercepted_call("free_sized");
+
+  if (REAL(free_sized))
----------------
jcking wrote:

On ELF-based systems, like Linux, the interception code doesn't require that the underlying real function actually exist. This will result in the real function pointer being `nullptr`. In that case, we forward to `free` which we assume exists or we have bigger problems.

https://github.com/llvm/llvm-project/pull/145085