hstoreUniquePairs(Pairs *a, int32 l, int32 *buflen)
{
	Pairs	   *ptr,
			   *res;

	*buflen = 0;
	if (l < 2)
	{
		if (l == 1)
			*buflen = a->keylen + ((a->isnull) ? 0 : a->vallen);
		return l;
	}

	qsort((void *) a, l, sizeof(Pairs), comparePairs);
	ptr = a + 1;
	res = a;
	while (ptr - a < l)
	{
		if (ptr->keylen == res->keylen &&
			memcmp(ptr->key, res->key, res->keylen) == 0)
		{
			if (ptr->needfree)
			{
				pfree(ptr->key);
				pfree(ptr->val);
			}
		}
		else
		{
			*buflen += res->keylen + ((res->isnull) ? 0 : res->vallen);
			res++;
			memcpy(res, ptr, sizeof(Pairs));
		}

		ptr++;
	}

	*buflen += res->keylen + ((res->isnull) ? 0 : res->vallen);
	return res + 1 - a;
}

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