That is not a memory leak though! That's using/exposing an uninitialized buffer, which can happen even if you allocate and free your allocations correctly. Leaking the buffer would prevent the memory region from being allocated by another application, and would in fact prevent that from happening.

This is also something that Rust does protect against in safe code, by requiring initialization of all memory before use, or using MaybeUninit for buffers that aren't, where reading the buffer or asserting that it has been initialized is an unsafe operation.