Comment by asveikau

Just want to come back with a simple example.

This means if the program is multi threaded, you cannot rely on calling malloc in the child, because at the time of the fork another thread could have happened to be inside malloc doing manipulations on the global heap.

Which means, practically speaking, "don't allocate memory between fork and exec".

If you want to be overly literal as you have been, you can call mmap and it will give you new pages, but who is really doing that? Not the random shared library code you might want to call into. Hell, even a lot of libc calls malloc.

Which means it's not safe to do a random library call between fork and exec.

See where I'm going with this? That's if your program is multi threaded. If it isn't, these things are most likely fine.