circle_recv(PG_FUNCTION_ARGS)
{
	StringInfo	buf = (StringInfo) PG_GETARG_POINTER(0);
	CIRCLE	   *circle;

	circle = (CIRCLE *) palloc(sizeof(CIRCLE));

	circle->center.x = pq_getmsgfloat8(buf);
	circle->center.y = pq_getmsgfloat8(buf);
	circle->radius = pq_getmsgfloat8(buf);

	if (circle->radius < 0)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
				 errmsg("invalid radius in external \"circle\" value")));

	PG_RETURN_CIRCLE_P(circle);
}

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