Is there a standard pointer size declaration?

Question

I have a structure with padding in char(oops, my bad). I would like to subtract the size of the pointer. Do you know the standard pointer size declaration or the standard macro for this?

Answer 1

sizeof (void *)

Answer 2

Do you need an answer to the C-standard or an answer that works almost all the time?

Usually, all data pointers are the same size, which is equal sizeof(void*).

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Answer 3

, offsetof(), stddef.h:

#include <stdio.h>
#include <stddef.h>

int main(void)
{
    struct s {
        int i;
        char c;
        double d;
        char a[];
    };

    /* Output is compiler dependent */

    printf("offsets: i=%ld; c=%ld; d=%ld a=%ld\n",
            (long) offsetof(struct s, i),
            (long) offsetof(struct s, c),
            (long) offsetof(struct s, d),
            (long) offsetof(struct s, a));
    printf("sizeof(struct s)=%ld\n", (long) sizeof(struct s));

    return 0;
}

$ ./a.out
offsets: i=0; c=4; d=8 a=16
sizeof(struct s)=16

Answer 4

sizeof (void *).