As usual, I can't see your code from here so can't tell why it's segmentation faulting. if I had to guess, I'd guess you were feeding integers into crc_add instead of pointers to integers.

Code:

// For integers, objects, etc 
crc_add(&crc, &object, sizeof(object));
// for arrays
crc_add(&crc, array, sizeof(array));
// for a pointer
crc_add(&crc, pointer, sizeof(*pointer));
// for a string
crc_add(&crc, string, strlen(string));

This is all from basic understanding of pointers in the C language.