path_add(PG_FUNCTION_ARGS)
{
	PATH	   *p1 = PG_GETARG_PATH_P(0);
	PATH	   *p2 = PG_GETARG_PATH_P(1);
	PATH	   *result;
	int			size,
				base_size;
	int			i;

	if (p1->closed || p2->closed)
		PG_RETURN_NULL();

	base_size = sizeof(p1->p[0]) * (p1->npts + p2->npts);
	size = offsetof(PATH, p[0]) +base_size;

	/* Check for integer overflow */
	if (base_size / sizeof(p1->p[0]) != (p1->npts + p2->npts) ||
		size <= base_size)
		ereport(ERROR,
				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				 errmsg("too many points requested")));

	result = (PATH *) palloc(size);

	SET_VARSIZE(result, size);
	result->npts = (p1->npts + p2->npts);
	result->closed = p1->closed;
	/* prevent instability in unused pad bytes */
	result->dummy = 0;

	for (i = 0; i < p1->npts; i++)
	{
		result->p[i].x = p1->p[i].x;
		result->p[i].y = p1->p[i].y;
	}
	for (i = 0; i < p2->npts; i++)
	{
		result->p[i + p1->npts].x = p2->p[i].x;
		result->p[i + p1->npts].y = p2->p[i].y;
	}

	PG_RETURN_PATH_P(result);
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.