Re: [PATCH] sys/tree.h: Removed

Hi Joel,

On Jul 17 09:32, Joel Sherrill wrote:
> Sorry. This sounds snippy in retrospect.
> 
> Having sys/tree.h in libc puts us in a position where our libbsd package
> depends on an arbitrary version from libc rather than the sys/tree.h which
> comes with the FreeBSD version that each branch is based on. That makes
> multiple RTEMS core developers nervous that we are introducing an
> unnecessary mismatch. It may not cause problems but there is a risk and
> invalidates one of the major reasons we use FreeBSD code for TCP/IP, NFS,
> USB, etc.
> 
> At this point, the implementation in FreeBSD 12 does not match newlib.
> Folks have checked FreeBSD 13 and 14 which we will need to update to and
> sys/tree.h does not match.
> 
> This ignores the issue that RTEMS itself uses tree.h for some internal data
> structures and we should have more configuration control over that.
> Unintentional changes to the newlib version could impact RTEMS behavior or
> performance in unexpected ways. In retrospect, adding this to newlib and
> using it violated the rule we had long had for the core of RTEMS that we
> should avoid using libc and other external libraries. Inside the OS proper,
> we need to have more control and there may be odd restrictions that
> wouldn't apply to applications.
> 
> For RTEMS, Gedare added this as rtems/bsd-tree.h and changed the names to
> put it into a namespace so it doesn't conflict with sys/tree.h.
> 
> For RTEMS, the sys/tree.h file needs to come from the libbsd package so it
> can be version mated with the FreeBSD kernel code in use on that branch. If
> the libc has one version and libbsd has another, there is a conflict.
> 
> Acting in good faith, I posted a patch to re-add it to newlib but I do not
> know how to remove a standard lib/include file for a target. We really do
> not want it installed from libc.
> 
> Hopefully this is a little clearer.

This is fine, but still, keep in mind that you're creating a potential
breakage by removing sys/tree.h entirely for projects using it.

Given that Sebastian added the file in 2015, Cygwin came with sys/tree.h
since the next release after that.

There are certain projects out there actually using sys/tree.h if it is
available.  For instance, tmux, OpenBSD's file, and quite a few others.
In fact, I have no idea how many of the ~4000 packages on Cygwin (apart
from tmux) use that file.

Therefore just removing the file is kind of dangerous and could either
break a package or change its behaviour in subtil ways.

Having said that...

Given you have a workaround for RTEMS, we can just resurrect sys/tree.h,
but that's a bit underwhelming.

While I can easily imagine that sys/tree.h from FreeBSD got new APIs, I
can't believe that it actually broke the existing API in a
backward-incompatible way.

Either way, it would be nice if we could get an updated version of this
file rather than just the old version.  Would you mind?


Thanks,
Corinna