Re: PATCH: import move-if-change from gnulib (was: PATCH: PR binutils/12283: bfd/doc doesn't support parallel build)

[Steve Ellcey <sje@cup.hp.com>]

On Fri, 2011-01-28 at 21:14 +0100, Ralf Wildenhues wrote:

> 
> I have meanwhile added an improved and fixed version of my proposed
> patch to the (more complete) gnulib copy of move-if-change.  See here:
> http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/24860/focus=24865
> 
> I hereby propose to just import the gnulib copy into GCC and src,
> http://git.savannah.gnu.org/cgit/gnulib.git/tree/build-aux/move-if-change
> and document the change in status as below in patches to src/MAINTAINERS
> and GCC www.  (The Autoconf copy of move-if-change has been updated from
> the gnulib one anyway.)
> 
> Any reasons against doing so?
> 
> Thanks,
> Ralf

I have no objection to this change and I think it will fix things on
most platforms but I have found one platform where I still have a
problem.  On hppa*-*-hpux*, compiling the same program twice in a row
does not result in the exact same executable.  So even with this change
the cmp will fail and the build will still abort like it does now.
During a GCC bootstrap build we work around these issues by using:

cmp --ignore-initial=16

to compare stage2 and stage3 bits.  And we also have to do the GCC
compilation with -frandom-seed=fixed-seed to avoid other differences in
object files.

But for some reason doing both of these still didn't get this to work
for me on the hppa platform.  I was still getting failures in the cmp
check, even with the --ignore-initial flag and the use of -frandom-seed
when compiling chew.

I wonder if it would be reasonable to add a configure flag to bfd that
would enforce the chew dependency (--enable-parallel-doc or something
like that).  It would be off by default but if specified then we would
enforce the chew dependency and parallel builds would just work
normally.