can't happen

(programming)

The traditional program comment for code executed under a condition that should never be true, for example a file size computed as negative. Often, such a condition being true indicates data corruption or a faulty algorithm; it is almost always handled by emitting a fatal error message and terminating or crashing, since there is little else that can be done.

Some case variant of "can't happen" is also often the text emitted if the "impossible" error actually happens. Although "can't happen" events are genuinely infrequent in production code, programmers wise enough to check for them habitually are often surprised at how frequently they are triggered during development and how many headaches checking for them turns out to head off.

See also firewall code, professional programming.

Mentioned in ?

References in classic literature ?

It can't happen for some time," said the Tin Woodman, trying to speak cheerfully; "for we shall be able to keep Jinjur out of the palace until she manages to break down the doors.

View in context

And every time she had reflected that the days of romance are dead, and that that sort of thing can't happen nowadays.

View in context

He added: "This is embarrassing and there should be a system in place to make sure it can't happen again.

Council blunder leaves residents with wrong bills

And Mills warned: "The danger is that with a game like this you don't play how we set out to play, you try and do things you wouldn't normally do and that can't happen.

COOL HEADS KEY TO DERBY WIN; National League: Chester v Wrexham Mills: Dragons must maintain discipline

NNA - Future Bloc member Ahmad Fatfat said that the extension of the mandate of top Lebanese Army brass can't happen without the approval of his Hezbollah, explaining that General Michel Aoun's problem in this regard should accordingly be with his ally Hezbollah.

Fatfat from Saifi: Aoun's problem is with his allies

I feel sorry for him - we let him down in games; it can't happen again.

JANMAAT: PLAYERS LET BOSS DOWN

If this vaccine can be supplied at such a price in Northern Ireland I see no reason why it can't happen on this side of the border.

TD calls for brain bug vaccine deal

Insiders claimed that the 34-year-old singer was pretty upset when she got an email a couple of days later from Stefani saying that the playdate can't happen "not now and not ever".

Gwen Stefani, Pink in feud post 'playdate invite' rejection

We told him this can't happen as Home Minister ( Sushilkumar Shinde) had already announced," Shoaib Iqbal told M AIL T ODAY .

Iqbal and Shokeen brokered face- saver

That can't happen in football, that can't happen again in my career and it certainly can't happen next season.

Grant loves life at the Boro - but not in the Championship

He was a fit young man but we can't guarantee an acute injury can't happen - no doctor in the world can guarantee an acute injury can't happen.

Norgrove death highlights the dangers of boxing - Smith

Last year we recovered eight points in six games so I don't know why it can't happen this year.