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I'm wondering what the rationale is for the usage of `goto` in the C source? It looks like it's exclusively used to implement a pattern of exiting or failing ea

I'm wondering what the rationale is for the usage of `goto` in the C source? It looks like it's exclusively used to implement a pattern of exiting or failing early and in a common way. Is this something that's common in modern C?

saynsedit 10y ago
Yes, goto exit and cleanup resources on error is a common and not frowned upon idiom in C. See Python source.
- creshal 10y ago
  Or the Linux kernel. (Or Apple's "goto fail" bug for a somewhat infamous example how to not use it.)
  - krylon 10y ago
    > Or Apple's "goto fail" bug for a somewhat infamous example how to not use it. But that problem was not because of the goto, strictly speaking.
rossy 10y ago
I'm not entirely sure how common it is in modern projects, but I use it a lot. I find functions that use this kind of centralized cleanup code a lot easier to read than functions that avoid 'goto' by duplicating the cleanup code or handling errors with deep nested if blocks. The Linux kernel coding style guide recommends it as well (see "Centralized exiting of functions" in https://www.kernel.org/doc/Documentation/CodingStyle https://www.kernel.org/doc/Documentation/CodingStyle) FWIW, it seems to be the primary use of 'goto' in these projects: https://github.com/torvalds/linux/search?q=goto https://github.com/torvalds/linux/search?q=goto https://github.com/FFmpeg/FFmpeg/search?q=goto https://github.com/FFmpeg/FFmpeg/search?q=goto https://github.com/antirez/redis/search?q=goto https://github.com/antirez/redis/search?q=goto
mhogomchungu 10y ago
I dont use "goto" in C but a specialized static function that does more or less the same thing. Example is the zuluExit "goto" function: https://github.com/mhogomchungu/zuluCrypt/blob/master/zuluCrypt-cli/lib/open_volume.c https://github.com/mhogomchungu/zuluCrypt/blob/master/zuluCr...
- ryan-c 10y ago
  I don't think that solution works well in general. If you want to do cleanup of local variables, I don't see how you'd do that with a static function unless you're using globals everywhere, some awful god object, or terrible varargs hacks.

saynsedit 10y ago

Yes, goto exit and cleanup resources on error is a common and not frowned upon idiom in C. See Python source.

creshal 10y ago
Or the Linux kernel. (Or Apple's "goto fail" bug for a somewhat infamous example how to not use it.)
- krylon 10y ago
  > Or Apple's "goto fail" bug for a somewhat infamous example how to not use it. But that problem was not because of the goto, strictly speaking.

rossy 10y ago

I'm not entirely sure how common it is in modern projects, but I use it a lot. I find functions that use this kind of centralized cleanup code a lot easier to read than functions that avoid 'goto' by duplicating the cleanup code or handling errors with deep nested if blocks. The Linux kernel coding style guide recommends it as well (see "Centralized exiting of functions" in https://www.kernel.org/doc/Documentation/CodingStyle https://www.kernel.org/doc/Documentation/CodingStyle) FWIW, it seems to be the primary use of 'goto' in these projects: https://github.com/torvalds/linux/search?q=goto https://github.com/torvalds/linux/search?q=goto https://github.com/FFmpeg/FFmpeg/search?q=goto https://github.com/FFmpeg/FFmpeg/search?q=goto https://github.com/antirez/redis/search?q=goto https://github.com/antirez/redis/search?q=goto

mhogomchungu 10y ago

I dont use "goto" in C but a specialized static function that does more or less the same thing. Example is the zuluExit "goto" function: https://github.com/mhogomchungu/zuluCrypt/blob/master/zuluCrypt-cli/lib/open_volume.c https://github.com/mhogomchungu/zuluCrypt/blob/master/zuluCr...

ryan-c 10y ago
I don't think that solution works well in general. If you want to do cleanup of local variables, I don't see how you'd do that with a static function unless you're using globals everywhere, some awful god object, or terrible varargs hacks.