Why there is no error when passing command line arguments when declaring main as `int main(void)`?

Question

Case 1:

void hello(void) {
    //something
}

int main()
{
    hello(1); //error
    return 0;
}

Case 2:

int main(void) {
    //something
    return 0;
}

Execution:

./a.out something something //No error, Why?

Why there is no error? main will not be able to take any arguments. So why it is possible to provide arguments from the command line?

Answer 1

Because the C compiler and the command line interpreter (or whatever is used to invoke your program) are different things.

The C language allows various ways how main () could be declared.

The command line interpreter will make any arguments available to the program. If the program ignores them, that's none of its business.

The command line interpreter doesn't even know that you used C to compile your program. On my computer, the program could be written in C, C++, Objective-C, Objective-C++, Swift, Fortran, Ada, and so on. Each of these compilers may or may not do things to accept commands from the command line.

Answer 2

Not checking the specification nor compiled result, it will cause no error because the C runtime will get the arguments and pass them to main(), but this type of main() will ignore the passed arguments, and if it is caller's duty to clean up the memory (stack) used as the arguments, it will cause no problems just as getting some arguments and not using them in the code.

This code won't emit errors in C:

void hello(); // in C, the compiler won't check arguments

int main() {
    hello(1); //no error
    return 0;
}

void hello(void) {
    //something 
}