Why is this program's output different between C and C++? [duplicate]

Question

Possible Duplicate:
Size of character ('a') in C/C++

The following program

#include <stdio.h>

int main()
{
    printf("%d\n", sizeof('\0'));
    printf("%d\n", sizeof(0));
}

compiled with gcc outputs

4
4

and with g++

1
4

Why is this happening? I know this it's not a compiler thing but a difference between C and C++ but what's the reason?

Answer 1

In C, character constants have type int per 6.4.4.4(10) of the standard,

An integer character constant has type int. The value of an integer character constant containing a single character that maps to a single-byte execution character is the numerical value of the representation of the mapped character interpreted as an integer.

Thus you're printing out the size of an int twice.

In C++, character constants have type char.

Answer 2

The \0 character literal is treated as an int in C, so you actually end up printing sizeof(int) instead of sizeof(char).

ideone gives the same results (C, C++).

Answer 3

In C character literals are ints. In C++ they are chars.