Thread: Can't piece together this code

Hello,

Does this code look sane? I'm supposed to be checking mirrored values for card images that will be emulated and I am not sure of the pointer arithmetic performed on LHS, RHS memset values. buf is a fixed with integer pointer malloc'd some multiple of 2, seems to me we're comparing the same memory?

Code:

int check_buf(void *buf, int size, int full_size)
{   
    if (size / 2 && memcmp(buf, buf + size / 2, size / 2) == 0)
    {
        if (!check_buf(buf, size / 2, full_size))
        {
            printf("Mirrored memory.");
            assert(0);
        }
        return 1;
    }
    else
    {
        return 0;
    }
}

Best

When posting code, try to make a minimally complete example out of it.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>

int check_buf(void *buf, int size, int full_size)
{   
    if (size / 2 && memcmp(buf, buf + size / 2, size / 2) == 0)
    {
        if (!check_buf(buf, size / 2, full_size))
        {
            printf("Mirrored memory.");
            assert(0);
        }
        return 1;
    }
    else
    {
        return 0;
    }
}

int main()
{
    char buff1[] = "ABCDDCBA";
    char buff2[] = "12345678";
    char buff3[] = "AAAAAAAA";
    printf("R1=%d\n", check_buf(buff1, 8, 8));
    printf("R2=%d\n", check_buf(buff2, 8, 8));
    printf("R3=%d\n", check_buf(buff3, 8, 8));
    return 0;
}


$ gcc -Wall foo.c
$ ./a.out 
R1=0
R2=0
a.out: foo.c:13: check_buf: Assertion `0' failed.
Aborted (core dumped)

2. Calling assert is dumb.
You do all that work and bomb out with a segfault.

3. Cite your source. I'm assuming you found this code somewhere and are confused.
Knowing the context of how it is used where you found it could be useful.

> Does this code look sane?
The recursion is weird to say the least.

> I'm supposed to be checking mirrored values for card images
Define "mirrored".

To me, two mirrored memory cards would compare identical with a single memcmp.
All this size/2 and recursion is baffling.