> Yes: OSX on ARM64 has alignof(max_align_t)==8 and alignof(__int128)==16. And malloc only provides 8-byte alignment, so if you're using types that require 16-b

> Yes: OSX on ARM64 has alignof(max_align_t)==8 and alignof(__int128)==16. And malloc only provides 8-byte alignment, so if you're using types that require 16-byte alignment, you have to call aligned_alloc. Also, the stack is only 8-byte aligned. Huh? Stack alignment is 16B ("The stack pointer on Apple platforms follows the ARM64 standard ABI and requires 16-byte alignment." https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms https://developer.apple.com/documentation/xcode/writing-arm6...) and memory returned by the system malloc is always 16B aligned (it was 16B aligned even on 32b x86 and ARM).