Comment by ghswa

I'm enjoying this so far although a couple of things have made me scratch my head in the example code allocating a vector.

  int create_vector(struct vector *vc, int size) {

    vc->data = 0;
    vc->size = 0;

    if (vc == NULL) {
      return VECTOR_NULL_ERROR;
    }

    /* check for integer and SIZE_MAX overflow */
    if (size == 0 || size > SIZE_MAX) {
      errno = ENOMEM;
      return VECTOR_SIZE_ERROR;
    }

Accessing the fields of vc before the NULL check seems like an error. Also, would it not be simpler to change type of the size parameter to size_t so that it's the same type as the size field of the vector struct?