adding #[track_caller] to #[global_allocator] to trace allocation source

[Geal]

Hello,
I am using a custom allocator to trace allocations and deallocations when debugging code. I was wondering if adding #[track_caller] to the GlobalAlloc::alloc and GlobalAlloc::dealloc methods could give me the origin of allocations (even if it ends up in libstd), but unfortunately, it only gives me the position of the #[global_allocator] attribute.

As an alternative, I am trying to obtain it with the backtrace crate, but apparently I cannot resolve the symbols for a stackframe (I suspect it would allocate), so I would need to store the instruction address at runtime, and post process the result with gimli.

Making #[track_caller] usable from a custom allocator would simplify a lot that use case, since everything returned by panic::Location::caller() is 'static, so there are no allocations.

So I'm not sure if this request fits the use case of #[track_caller] but I'm probably not the only one wanting a nice way to track allocations :)

[anp]

This would be cool but I'm not sure it can be supported backwards-compatibly (see #74763 also). AIUI, it would require adding the attribute to symbols that are exposed as externs which would be a breaking change.

[Geal]

I see, it was a fun thought only :)