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main function return in a C program?
void main is bad?
Q: If void main is incorrect, how come the compiler lets it compile?
main function be declared in one of the following two ways:
int main (void);
or
int main (int argc, char **argv);
In both cases the return type is an int, and your main function should therefore either return an int or call the library function exit, when the
program ends.
Since the runtime environment assumes that main returns an int, declaring main with any other return type, including void, invites trouble. The
compiler might compile such a program, since the ANSI Standard doesn't require it to fail, but the behavior of such a program is, in the Standard's parlance, "undefined" (read: anything can
happen). That is why GCC will print a warning in these cases if you use the -Wall switch.
To summarize, using void main is unsafe and can potentially do evil things to your program. It is best to avoid it.
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