malloc_history equivalent

[davidchisnall]

The Darwin malloc implementation has a feature (enabled by an environment variable) that records, for each allocation or deallocation event:

• The size of the allocation.
• The address of the allocation.
• The thread ID for the [de]allocation call.
• A stack trace at the [de]allocation site.

This makes it possible for after a crash to determine where an allocation originated and where it was freed.

Implementing similar functionality in snmalloc (ideally using ifunc logic to replace the malloc / free functions at load time) could reuse some of the compressed stack trace logic from the LLVM sanitisers.