main和main（）之间的区别

Question

The following code 1 is fine

#include <stdio.h>    // code 1
main()
{
    printf("%u",main);
}

but this code 2 gives segmentation fault.

#include <stdio.h>  // code 2
main()
{
    printf("%u",main());
}

I'm not getting what's the difference between main and main()?

Answer 1

Did you compile with all warnings enabled from your compiler? With gcc that means giving the -Wall argument to gcc (and -g is useful for debugging info).

First, your printf("%u", main) should be printf("%p\\n", main) . The %p prints a pointer (technically function pointers are not data pointers as needed for %p , practically they often have the same size and similar representation), and you should end your format strings with newline \\n . This takes the address of the main function and passes that address to printf .

Then, your second printf("%u", main()) is calling printf with an argument obtained by a recursive call to the main function. This recursion never ends, and you blow up your call stack (ie have a stack overflow), so get a SIGSEGV on Unix.

Pedantically, main is a very special name for C standard, and you probably should not call it (it is called auto-magically by startup code in crt0.o ). Recursing on main is very bad taste and may be illegal.

See also my other answer here .