That's because windows uses a threaded model, mandatory locking and various other design practices that were regarded as too complex by most *nix OS designers in regards to userspace applications.

I'd submit, humbly, that in my experience with MS products they were not far wrong.

If there is no particular reason that you are using fork() and exec() to create the child process, you could make your child.c a non-main function and, instead of exec()-ing it, call it as a function after the fork():

// in main

if ( 0 == (pid = fork() ))
child(int values_needed, ..., int *value_to_return);
exit(...);
else
// parent code here.

This WILL solve your problem without IPC or shared memory if you simply pass parameters to the child.

Hope this helps.

Stewartw