pair_count(char *s, char delim)
{
	int			ndelim = 0;

	while ((s = strchr(s, delim)) != NULL)
	{
		ndelim++;
		s++;
	}
	return (ndelim % 2) ? ((ndelim + 1) / 2) : -1;
}

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