libc: group database

[b0inbot]

Group database support via libc config, implementation of common grp.h functions.

Additionally fixed getpwent.run test to confirm parity with passwd support.

[nfeske]

From a quick glance, your patch looks very nice. Special thanks for adding the test. The commit will get a more thorough review by the end of next week.

What was your intention behind turning the regular text (T) symbols into weak symbols (W)?

[b0inbot]

What was your intention behind turning the regular text (T) symbols into weak symbols (W)?

I thought they would have to be but I admit I did not fully understand. The other genode-specific methods of the libc, like getpwnam, are weak symbols.

Catching up via wikipedia... https://en.wikipedia.org/wiki/Weak_symbol

Weak symbols can be used as a mechanism to provide default implementations of functions that can be replaced by more specialized (e.g. optimized) ones at link-time. The default implementation is then declared as weak, and, on certain targets, object files with strongly declared symbols are added to the linker command line.

If a library defines a symbol as weak, a program that links that library is free to provide a strong one for, say, customization purposes.

I think this is all not relevant since the libc is provided at runtime via a ROM?

[b0inbot]

It is not necessary but since much of this was a copy-paste job, feel free to rename the \author Boin lines to \author Norman Feske as that is who is listed in the getpwent.cc files. Do whatever feels best.