[libc++] Disable CFI in __libcpp_allocate

[ldionne]

Since we're casting uninitialized memory, we must disable CFI checks.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

Changes

Since we're casting uninitialized memory, we must disable CFI checks.

---

Full diff: https://github.com/llvm/llvm-project/pull/124805.diff

1 Files Affected:

• (modified) libcxx/include/__new/allocate.h (+2-1)

diff --git a/libcxx/include/__new/allocate.h b/libcxx/include/__new/allocate.h
index a64663c09fa35d..738fa62af4d61d 100644
--- a/libcxx/include/__new/allocate.h
+++ b/libcxx/include/__new/allocate.h
@@ -50,7 +50,8 @@ _LIBCPP_HIDE_FROM_ABI void __libcpp_operator_delete(_Args... __args) _NOEXCEPT {
 }
 
 template <class _Tp>
-inline _LIBCPP_HIDE_FROM_ABI _Tp* __libcpp_allocate(__element_count __n, size_t __align = _LIBCPP_ALIGNOF(_Tp)) {
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_NO_CFI _Tp*
+__libcpp_allocate(__element_count __n, size_t __align = _LIBCPP_ALIGNOF(_Tp)) {
   size_t __size = static_cast<size_t>(__n) * sizeof(_Tp);
 #if _LIBCPP_HAS_ALIGNED_ALLOCATION
   if (__is_overaligned_for_new(__align)) {

[philnik777]

@ldionne Could we maybe look into adding a bot for CFI? It's not the first time there is some issue with it, and I don't think there's a fundamental problem with enabling it.

[philnik777]

Looks like you're already working on it in #124837 :D