Function dealloc_for_layout 

pub unsafe fn dealloc_for_layout(ptr: PtrMut, layout: Layout)

Deallocates memory for a layout, correctly handling zero-sized types.

For ZSTs (zero-sized types), this is a no-op since no memory was actually allocated. This avoids undefined behavior since alloc::alloc::dealloc with a zero-sized layout is UB.

Safety

• For non-ZST layouts, ptr must have been allocated by alloc_for_layout (or alloc::alloc::alloc) with the same layout.
• ptr must not have been deallocated already.
• For ZST layouts, ptr is ignored (should be the dangling pointer from alloc_for_layout, but this isn’t checked).