The ABI doesn't mandate were locals are located on a stack frame thought so I'm not sure how would you inspect those. If you simply meant that you want rely on

The ABI doesn't mandate were locals are located on a stack frame thought so I'm not sure how would you inspect those. If you simply meant that you want rely on an ABI, then that's fine, although relying on those details might be UB for standard conforming code, it is obviously well defined for compilers that conform to the ABI. Just because it is undefined from a standard point of view, doesn't mean is still undefined for a specific compiler + platform. You will still need to use compilation firewalls and barriers to avoid aliasing or pointer provenance issues of course.