I'm not sure if I'm using diffseq correctly here, but comparing two vectors of different lengths and no common elements seems to cause a segfault, as in the following toy example:
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <stdbool.h>
#include "minmax.h"
#define ELEMENT char
#define EQUAL(a,b) (a == b)
#define OFFSET ssize_t
#define USE_HEURISTIC
#define EXTRA_CONTEXT_FIELDS
#define NOTE_INSERT(ctxt,xoff)
#define NOTE_DELETE(ctxt,yoff)
#define lint
#include "diffseq.h"
int
main(void)
{
char *expected = "abcd";
char *actual = "efg";
ssize_t expected_limit = 4;
ssize_t actual_limit = 3;
ssize_t *work_buffer;
struct context ctxt;
/* Allocate a work buffer */
work_buffer = calloc(2 * (expected_limit + actual_limit + 3), sizeof(ssize_t));
/* Call the Gnulib diff algorithm */
ctxt.xvec = expected;
ctxt.yvec = actual;
ctxt.fdiag = work_buffer + actual_limit + 1;
ctxt.bdiag = work_buffer + expected_limit + actual_limit + 3;
ctxt.heuristic = 1;
compareseq(0, expected_limit, 0, actual_limit, &ctxt);
free(work_buffer);
return 0;
}
This seems to be because diag() doesn't find a point of correspondence and therefore the comparison proceeds with garbage. Specifically, dmin is initialized to a negative value at the start of diag(). However, the comment at the top of diag() does say
> Compare in detail contiguous subsequences of the two vectors which are known, as a whole, to match each other.
and of course, I do know in this toy example that the vectors don't match each other as a whole. Am I trying to do something that diffseq isn't meant to do?
Regards,
--
Philip