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

On 21/6/2024 8:21 am, Joel Sherrill wrote:
> On Thu, Jun 20, 2024 at 4:13 AM Sebastian Huber
> <[email protected] <mailto:[email protected]>>
> wrote:
> 
>     On 18.06.24 22:25, Joel Sherrill wrote:
>     > This file was from a specific older FreeBSD version. There have been
>     > multiple changes to this file with FreeBSD 14 including breaking
>     > changes to the file.
> 
>     What kind of breaking changes did you observe in the FreeBSD 14 version
>     of <sys/tree.h>? I see no breaking API changes. FreeBSD changed the
>     implementation to use rank-balanced trees instead of red-black trees,
>     but this should not have resulted in API breaks (the ABI changed though).
> 
> This creates a conflict between the libc and rtems-libbsd versions. When 
> both are installed, the header installed by libbsd results in different code
> than the version RTEMS was compiled with. 
> 
> Using this internally in RTEMS, we opened ourselves to external changes 
> impacting the score implementation of rbtree.  This leaves us
> open to external changes having an impact on performance. 
> We should take on the preferred implementation inside the score of 
> RTEMS so we have control. We will end up having to do something
> with the file name and name space.
> 
> This actually violated a core development principle for RTEMS and
> we should have spotted this long ago. Everything in the score and
> "bottom" of RTEMS should not depend on libc. 
> 
> We need to control the implementation used internal to RTEMS.
> Realizing that it was not up date in newlib just triggered the realization
> that we should not have been using it.

This file is not referenced in newlib and so serves no direct purpose. We have a
MR in RTEMS to copy this file into the score renaming it to bsd-tree.h so there
is no clash. This means RTEMS's kernel will not depend on this file as it
currently does once the MR is merged.

I think newlib users should expect libc and libm interfaces and be free to bring
a sys/tree.h from the BSD of their choice into their code base. This file here
limits that and limits anyone who decides to use BSD sources such as networking.

Chris