txid_current(PG_FUNCTION_ARGS)
{
	txid		val;
	TxidEpoch	state;

	/*
	 * Must prevent during recovery because if an xid is not assigned we try
	 * to assign one, which would fail. Programs already rely on this function
	 * to always return a valid current xid, so we should not change this to
	 * return NULL or similar invalid xid.
	 */
	PreventCommandDuringRecovery("txid_current()");

	load_xid_epoch(&state);

	val = convert_xid(GetTopTransactionId(), &state);

	PG_RETURN_INT64(val);
}

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