On Linux, threads are implemented in terms of processes. In other words, threads are really just a fork() with mostly shared memory, instead of completely copy-on-write memory. What this means, is that when you use fork() in a thread (main or other), you end up copying the entire shared memory space of all of the threads, and the thread specific storage of the thread you call fork() from.
Now all of this sounds good, but that doesn't mean that this is what will happen or work well. If you want to make a cloned process, try to do a fork before starting any other threads, and then use read-only virtual memory to keep the forked process up to date with current memory values.
So although it may work, I just suggest testing, and try to find another way first. And be prepared for a lot of:
Segmentation fault
