How does TSTP (polite pause) interact with my C++ program in linux?

Question

I have written a C++ program and I am executing in the gnome terminal (I am on Ubuntu). I press Ctrl + Z, which suspends the process. Later on, I execute % on the same terminal, which resumes execution.

From what I've read, Ctrl+Z sends a TSTP signals to the process, which tells it to stop execution. But TSTP is polite, in the sense that the process is allowed to continue until it decides it can stop. In my C++ program code, I didn't do anything to explicitly deal with TSTP signals. So, my question is, what things inside my C++ code will continue running in spite of the TSTP signal? For example, if I have a file stream open, will it wait until it is closed? I expect an overall answer, not too deep or covering all the details. I just want an idea of how this happens.

Answer 1

Your program continues running while the SIGTSTP handler executes. Since you haven't set one up, you get the default signal handling behavior, which is for the process to be stopped.

While your process is stopped, it simply isn't scheduled for execution. Files don't get closed, nor is stopping delayed until files get closed (unless done in the signal handler).

This website looks like it has a helpful explanation of how a handler can be installed to perform some tasks and then have the default stopping behavior:

• http://man7.org/tlpi/code/online/dist/pgsjc/handling_SIGTSTP.c.html