Can sizeof return 0 (zero)

Question

Is it possible for the sizeof operator to ever return 0 (zero) in C or C++? If it is possible, is it correct from a standards point of view?

Answer 1

Here's a test, where sizeof yields 0

#include <stdio.h>

void func(int i)
{
        int vla[i];
        printf ("%u\n",(unsigned)sizeof vla);
}


int main(void)
{

        func(0);
        return 0;
}

Answer 2

in my view, it is better that sizeof returns 0 for a structure of size 0 (in the spirit of c). but then the programmer has to be careful when he takes the sizeof an empty struct.

but it may cause a problem. when array of such structures is defined, then

&arr[1] == &arr[2] == &arr[0]

which makes them lose their identities.

i guess this doesnt directly answer your question, whether it is possible or not. well that may be possible depending on the compiler. (as said in Michael's answer above).

Answer 3

sizeof never returns 0 in C and in C++. Every time you see sizeof evaluating to 0 it is a bug/glitch/extension of a specific compiler that has nothing to do with the language.

Answer 4

struct Empty {
} em;

struct Zero {
    Empty a[0];
} zr;

printf("em=%d\n", sizeof(em));
printf("zr=%d\n", sizeof(zr));

Result:

em=1
zr=0