Include errno (and strerror) in sys errors

[lucasb-eyer]

Hi,

Today I spent considerable amount of time trying to figure out why almost all julia fs functions failed after a certain (nondeterministic) point in my program. The answer lies in errno: 24: "Too many files open".

If all functions included errno info in those errors which follow from a C call, this would have been a no-brainer. One example is readdir, just doing error("unable to read directory $path") instead of providing additional useful errno diagnostic.

I could change that and other occurrences to systemerror("unable to read directory $path", file_count < 0), but before I spend time on this, I'd like to know if it is at all wanted?

[StefanKarpinski]

Yes, this would be great. I've tried to be systematic (get it?) about using systemerror wherever appropriate, but there's a lot of uses in Base that don't have this. Improving that would be a valuable contribution.

[lucasb-eyer]

Guess we can close this now.