I’ve used this before in embedded code to save rom space by not having to include malloc. The stack _is_ the heap! Just have to be very careful about when you can call another function.

The best version of this is where you allocate a block on your stack then pass that as a pointer up to the next function to use. The one who owns the memory is the one who allocates it (Rust style?). Or, have the linker allocate global blocks works too.