[core] Disable R__SIZEDDELETE definition for macOS 26 beta

[devajithvs]

MacOS 26.0 beta fails to build without this

This along with #18235 should fix MacOs 26.0 builds

This snippet fails to compile with the latest beta (unless we pass -fsized-deallocation):

#include <new>
int main() {
    void* ptr = nullptr;
    size_t size = 10;
    ::operator delete(ptr, size);
    return 0;
}

This Pull request:

Changes or fixes:

Checklist:

• tested changes locally
• updated the docs (if necessary)

This PR fixes #

[hahnjo]

Can you try just

#ifdef __cpp_sized_deallocation
#   define R__SIZEDDELETE
#endif

As far as I understand llvm/llvm-project@ef804d8, libc++ will now also honor the feature flag so my change from commit b5ad658 can be simplified even more.

[github-actions]

Test Results

    18 files      18 suites   3d 8h 44m 18s ⏱️
 2 811 tests  2 811 ✅ 0 💤 0 ❌
49 162 runs  49 162 ✅ 0 💤 0 ❌

Results for commit 7d50deb.

♻️ This comment has been updated with latest results.

[devajithvs]

Can you try just

#ifdef __cpp_sized_deallocation
#   define R__SIZEDDELETE
#endif

As far as I understand llvm/llvm-project@ef804d8, libc++ will now also honor feature flag so my change from commit b5ad658 can be simplified even more.

Thanks Jonas!

[hahnjo]

Looks like we need a new reference file for macOS... Though it's curious that the functions are still universally there on Linux, I thought that -fsized-deallocation is not the default

[hahnjo]

LGTM. If needed, we can tweak choosing the reference file in the future, for example if some configuration on Linux doesn't enable __cpp_sized_deallocation either

[hahnjo]

I'm seeing a local failure of roottest-root-meta-runMemberComments with Clang 18. I'm proposing to globally enable sized deallocation in #19053.