Comment by knome

3 months ago

https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html

'computed goto' is used in gcc to mean the same as assigned goto in Fortran. The Fortran variation appears to have more restrictions than the gnuc one.

5 comments

knome

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johnisgood  3 months ago

I may be dumb, but what is "goto *ptr;" useful for? Or &&foo.

  • trealira  3 months ago

    It's used in VMs, emulators, and other interpreters for making a dispatch loop with less branching than a standard loop with a switch inside it.

    https://eli.thegreenplace.net/2012/07/12/computed-goto-for-e...

    • rurban  3 months ago

      No, it has the same number of branches as a switch inside. The only difference is that computed goto switches miss the initial range check. And proper switch implementations by a better compiler would be more optimizable. But we are waiting more than 20 years for that already. Sparse switch dispatch tables are also compiled horribly.

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  • withinboredom  3 months ago

    error conditions when you don't have exceptions:

        goto *errOrSuccess;

    is a pretty normal one. This basically allows you to emulate a "finally".

    State machines are another big one, which look much nicer with computed goto than a switch statement.