Fix Bugzilla issue 24404 - ifaddrs union fields incorrectly name on Linux.

[jmdavis]

You can see the correct declaration for ifaddrs on Linux here:

https://www.man7.org/linux/man-pages/man3/getifaddrs.3.html

What the fields are supposed to be named is ifa_broadaddr and ifa_dstaddr. However, because Linux defines them using a union, it gives them different names within the union - ifu_broadaddr and ifu_dstaddr - and then #defines the proper names to access the union names.

What druntime did was use the union names - and then incorrectly name ifu_dtsaddr as if_dstaddr. So, it was doubly wrong for that field.

The two approaches that we could take here would be to either

1. Turn the union into a type so that we could have an ifa_ifu field to allow accessing the ifu_* names that way - as is technically possible in C - and then add wrapper functions with the ifa_* names (since we couldn't use an alias to access members of the union member variable).

2. Just rename the fields to ifa_* and ignore the fact that you can technically access the ifu_* fields via the union name in C.

The simpler approach is #2, so that's what this commit does. I'm pretty sure that the ability to access the ifu_* fields via the union name is just an implementation detail - particularly since other platforms just declare the ifa_* names without using a union at all.

Either way, deprecated aliases are provided so that existing code doesn't break.

[dlang-bot]

Thanks for your pull request, @jmdavis!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24404	normal	The names of the union fields in Linux's ifaddrs are named incorrectly.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#16233"