Forbid Window re-size

Hi! I need to create a window wich size must be constant. The program must not allow to change the size, but I have no idea how to do it.
I’ve tried with the reshape function, but I don’t know how to do it.
Can anybody help me?

This depends on your window manager, not GL.

I know it can be done with GL instructions, but I don’t know which ones. glutReshapeFunc is involved, but I don’t know how use it for this objective.
I’ve tried almost everything, changing the parameters to glViewPort, glutReshapeFunc, glutWindowSize(now I know it doesn’t exist)…
I don’t know what else I can do.

I’ve found the instruction. It is glutWindowReshape.

This is not a ‘GL instruction’.