Function call syntax [duplicate]

Question

I'm analyzing a C program in which I find a strange fucntion call here is the function definition :

static void endSignal (int32_t dummy) { if (nTerminating) return; nTerminating=1; printf("terminating....\n"); terminateDLNAsystem(); sleep(1); exit (0); }

This function takes an int32_t parameter ! Now this the main function calling "endSignal"

int32_t main (int32_t argc, char **argv) { /*Statements . . */ signal(SIGINT, endSignal); signal(SIGABRT, endSignal); signal(SIGQUIT, endSignal); signal(SIGTERM, endSignal); return 0; }

the main function call endSignal without any parameter, what happen in this case ?

It doesn't call endSignal, it passes the function as a parameter to another function. — StoryTeller - Unslander Monica
– StoryTeller - Unslander Monica, Commented Feb 17, 2017 at 13:14
The main prototype is not standard-conforming, BTW; main should return int and the first argument should be int; this in your question is an "other implementation defined manner". — Antti Haapala
– Antti Haapala, Commented Feb 17, 2017 at 13:14

Community · Accepted Answer · 2017-05-23 12:24:59Z

6

Main function calls signal functions and not endSignal.

endSignal is parameter acting as callback.

This is passing function pointers as arguments.

How do you pass a function as a parameter in C?

edited May 23, 2017 at 12:24

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answered Feb 17, 2017 at 13:14

unalignedmemoryaccess

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8 Comments

stojo304 Over a year ago

This is not the same case. in my case "signal" is a pre-defined function in <signal.h> so signal can't call the function endSignal to use it ..

unwind Over a year ago

@stojo304 This is exactly the right answer, and of course signal() can call its callback function, that's the whole point. Why shouldn't it be able to?

stojo304 Over a year ago

Yes i just read the definition of signal and understand this point, Thanks

stojo304 Over a year ago

@unwind , please what is the difference between : int *i[]= {1,1}; int j[]={2,2};

unalignedmemoryaccess Over a year ago

first is array of pointers, both points to value 1. In second case, you have 2 integer values, both are set to 1.

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