svn commit: r365836 - head/share/mk

[Rodney W. Grimes]

> On Thu, Sep 17, 2020 at 9:39 AM Steffen Nurpmeso <steffen at sdaoden.eu> wrote:
> 
> > Alex Richardson wrote in
> >  <202009171507.08HF7Qns080555 at repo.freebsd.org>:
> >  |Author: arichardson
> >  |Date: Thu Sep 17 15:07:25 2020
> >  |New Revision: 365836
> >  |URL: https://svnweb.freebsd.org/changeset/base/365836
> >  |
> >  |Log:
> >  |  Stop using lorder and ranlib when building libraries
> >  |
> >  |  Use of ranlib or lorder is no longer necessary with current linkers
> >  |  (probably anything newer than ~1990) and ar's ability to create an
> > object
> >  |  index and symbol table in the archive.
> >  |  Currently the build system uses lorder+tsort to sort the .o files in
> >  |  dependency order so that a single-pass linker can use them. However,
> >  |  we can use the -s flag to ar to add an index to the .a file which makes
> >  |  lorder unnecessary.
> >  |  Running ar -s is equivalent to running ranlib afterwards, so we can
> > also
> >  |  skip the ranlib invocation.
> >
> > That ranlib thing yes (for long indeed), but i have vague memories
> > that the tsort/lorder ordering was also meant to keep the things
> > which heavily interdepend nearby each other.  (Luckily Linux
> > always had at least tsort available.)
> > This no longer matters for all the platforms FreeBSD supports?
> >
> 
> tsort has no notion of how dependent the modules are, just an order that
> allows a single pass through the .a file (otherwise you'd need to list the
> .a file multiple times on the command line absent ranlib). That's the
> original purpose of tsort. tsort, lsort, and ranlib all arrived in 7th
> edition unix on a PDP-11, where size was more important than proximity to
> locations (modulo overlays, which this doesn't affect at all).
> 
> There were some issues of long vs short jumps on earlier architectures that
> this helped (since you could only jump 16MB, for example). However, there
> were workarounds for this issue on those platforms too. And if you have a
> program that this does make a difference, then you can still use
> tsort/lorder. They are still in the system.
> 
> I doubt you could measure a difference here today. I doubt, honestly, that
> anybody will notice at all.

The x86 archicture has relative jmps of differning lengths, even in long mode
there is support for rel8 and rel32.

> 
> Warner

-- 
Rod Grimes                                                 rgrimes at freebsd.org