[libc-commits] [libc] [libc] Expand usage of libc null checks. (PR #116262)

[via libc-commits]

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@@ -17,6 +18,8 @@ namespace LIBC_NAMESPACE_DECL {
 
 // TODO: Look at performance benefits of comparing words.
 LLVM_LIBC_FUNCTION(void *, memchr, (const void *src, int c, size_t n)) {
+  const unsigned char *src_cpy = (const unsigned char *)src;
+  LIBC_CRASH_ON_NULLPTR(src_cpy);
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lntue wrote:

The volatile load of nullptr (which is implementation-defined, not undefined behavior) was needed to preserve the crashing with SIGSEGV behavior that you might get when `func(nullptr)` was called with a dynamically linked glibc.  Without that, `__builtin_trap()` will crash with `SIGILL` instead.

So for the purpose of this PR, I think we should leave `LIBC_CRASH_ON_NULLPTR` macro definition as-is, and a further investigation to simplify the trapping behavior of the macro could be a follow up task / PR.

https://github.com/llvm/llvm-project/pull/116262