Is it possible to pass two arguments in c?

Question

I have written a C program where I declared a function reverse(int i). When I compile and run the program, it runs fine despite passing two arguments like this reverse((i++, i)). Why doesn't this cause a syntax error? reverse expects one argument.

  #include <stdio.h>
    void reverse(int i);
    int main()
    { 
            reverse(1); 

    }
    void reverse(int i)
    {
            if (i > 5)
                    return ;
            printf("%d ", i); 
            return reverse((i++, i));
    }

Passing `n` arguments to a function that accepts `k != n` arguments is not a syntax error, it's more of a type error (that is, semantics error). — ForceBru, May 06 '19 at 19:03
If an answer solved your question, you can mark it as an answer by pressing the gray tick to the left of the question. — alx - recommends codidact, May 06 '19 at 19:26

score 8 · Answer 1 · answered May 06 '19 at 18:57

8

You're not passing two arguments - that would be reverse(i++, i) (which incidentally would invoke undefined behaviour because of the lack of a sequence point between (i++ and i).

You're passing (i++, i) as a single argument. Since it is inside an additional pair of parentheses, the comma here does not separate the arguments of the function, but rather acts as the comma operator.

answered May 06 '19 at 18:57

sepp2k

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I got it now . Thanks for your reply – Deep Learner May 06 '19 at 19:10

Carcigenicate · Accepted Answer · 2019-05-06T19:03:43.187

5

(i++, i) seems to execute i++, then evaluate to i, the last operand to ,. You can see that here:

// Notice the ( , )
int i = (puts("Inside\n"), 2); // Prints "Inside"

printf("%d\n", i); // Prints 2

It didn't cause an error because you only passed one argument. That one argument though was a sequence of effects that evaluated to i.

edited May 06 '19 at 19:03

answered May 06 '19 at 18:57

Carcigenicate

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Is it possible to pass two arguments in c?

2 Answers2