Re: non C based environments can have problems [LWN.net]

Re: non C based environments can have problems

Posted Jan 24, 2007 21:13 UTC (Wed) by dododge (subscriber, #2870)
In reply to: Re: non C based environments can have problems by ldo
Parent article: LCA: How to improve Debian security

I think having a global errno is such a dumb idea. Why can't system and library calls directly return an error code?

Tradition.

Within the kernel, these sorts of functions typically do return error codes directly. But the userspace API is so ingrained that changing existing functions would break too much. As mentioned, even just changing errno from being a global int to a macro that produces an int (so that e.g. it can produce a different errno object for each thread) was enough to break some applications.

New APIs can of course use more sensible error reporting than errno if they want to. It could also be worse, though; for example the glibc obstack API by default aborts the program instead of returning an error, and while you can change that behavior you still have to rely on a global callback that at best uses something like setjmp/longjmp while running the risk of some library code changing the callback to something else. Yuck.

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