[libcxx-commits] [libcxx] [libcxx] Align `__recommend() + 1` by __endian_factor (PR #90292)

[Chris Kennelly via libcxx-commits]

ckennelly wrote:

I'm unable to say whether or not this is a problem for Google's codebase, since @alk speculated [upthread](https://github.com/llvm/llvm-project/pull/90292#issuecomment-2155502762) that it might be string ABI dependent.  I'll see if I can loop some folks in who would know.

Either way, sized deallocation is an important performance optimization in modern memory allocators to avoid a costly pointer-to-size lookup (in TCMalloc's case, a 2/3-level radix tree walk).  Passing the wrong size is UB and diagnosed by ASan as such, and in practice means we might place the deallocated object on the wrong freelist.

https://github.com/llvm/llvm-project/pull/90292