memcmp.c

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#include <string.h>

int __attribute__((weak)) memcmp(const void* p1, const void* p2, size_t n)
{
    size_t i;

    if(p1 == p2)
    {
        return 0;
    }

    if(!p1)
    {
        return 1;
    }

    if(!p2)
    {
        return -1;
    }

    // This for loop does the comparing and pointer moving...
    for(i = 0; (i < n) && (*(const uint8_t*)p1 == *(const uint8_t*)p2);
        i++, p1 = 1 + (const uint8_t*)p1, p2 = 1 + (const uint8_t*)p2)
    {
        // empty body
    }

    // if i == length, then we have passed the test
    return (i == n) ? 0 : (*(const uint8_t*)p1 - *(const uint8_t*)p2);
}