Never ending function problem

Question

Hi Guys,

Im trying to run a function that will never end (until the program is killed)

How would i start such a function and be able to continue on past that function, because at the moment the program will not run past the never ending function.

Regards

Paul

Answer 1

You'd need to start a new thread. A given thread can only execute one function at a time. So, if you want to have two separate functions executing at the same time, you need multiple threads. You'll need to look into multi-threaded programming. If you're on linux or another unix-based system, then the library to look at would be pthreads.

Answer 2

Fire it off in a thread. It would still, however, be really sensible to allow the function to exit.

Answer 3

An idea for a pseudo-thread based on a similar issue I needed to fix without threading (may or may not work for you):

1. Start the application.
2. when it gets to where the function is supposed to run, call a timer to start (very short time).
3. timer calls back and starts the never-ending function then quits.
4. Never-ending function includes a 10 ms sleep and a call to process all messages.

Answer 4

While I'd agree with everyone else that a thread is probably the easiest way to go, this scenario doesn't sound like something that should ever happen (at least not deliberately) - it sounds like this originates from a design problem.

Why do you need a function that will run forever? What does this function do? There may be a more appropriate programming model, such as a Windows service or a daemon process. Also, it's usually better to send the thread a signal that it's time to end, and have the thread do it's thing until it receives such a message (rather than just force-killing it when the app exits).

I don't know enough about what you're trying to do here, but I'd suggest examining your design and see if there's a better way.

Answer 5

Executing "past" a never-ending function isn't possible (if it doesn't end, you can't move past it). I am assuming that you want to have some code running in a loop in the background while your program does something else.

You want something like this:

#include <pthread.h>

int endLoop;

void* backgroundLoop(void* arg) {
    while (!endLoop) {
        ...
    }
    return NULL;
}

int main (int argc, char** argv) {
    pthread_t thread;
    int retval;
    ...
    // Launch background thread
    endLoop = 0;
    retval = pthread_create(&thread, NULL, backgroundLoop, NULL);

    // Continue with main function
    ...
    // Force background loop to end
    endLoop = 1;

}

If you are using pthreads, you can find more info here. If you are using some other thread library, the concept will be similar but the thread create/destroy functions may look different.