RFC: Update top level libtool files

[Joseph Myers]

On Tue, 10 Oct 2017, Nick Clifton wrote:

> Hi Guys,
> 
>   I would like to update the top level libtool files (libtool.m4,
>   ltoptions.m4, ltsugar.m4, ltversion.m4 and lt~obsolete.m4) used by
>   gcc, gdb and binutils.  Currently we have version 2.2.7a installed in
>   the source trees and I would like to switch to the latest official
>   version: 2.4.6.

As per previous discussions on the issue: it's necessary to revert libtool 
commit 3334f7ed5851ef1e96b052f2984c4acdbf39e20c, see 
<https://gcc.gnu.org/ml/gcc-patches/2011-01/msg00520.html>.  I do not know 
if there are other local libtool changes that are not in version 2.4.6; it 
would be necessary to check all differences from 2.2.7a to determine 
whether any need to be re-applied to 2.4.6.

>   I have successfully run an x86_64 gcc bootstrap, built and tested lots
>   of different binutils configurations, and built and run an x86_64 gdb.

Testing cross compilers, including Canadian crosses, would be important as 
well.

>   One thing that worries me though, is why hasn't this been done before?
>   Ie is there a special reason for staying with the old 2.2.7a libtool ?
>   If not, then does anyone object to my upgrading the gcc, gdb and
>   binutils mainline sources ?

Given appropriate testing and checks of local libtool changes, I think 
such updates are a good idea.  (As, for that matter, would be resyncing 
the toplevel configure/build code in the newlib-cygwin repository with 
that in GCC and binutils-gdb - but I don't know if newlib-cygwin has any 
unique local patches not in the other repositories, and given the 
out-of-sync nature at present I don't think such a resync can be required 
as part of an update in GCC and binutils-gdb.)

For that matter, these trees are also using very old autoconf and automake 
versions and using the current versions of those (2.69 and 1.15.1) would 
be a good idea as well.  Hopefully version dependencies are loose enough 
that it's possible to update one tool at a time (so update libtool without 
needing to update autoconf or automake at the same time).

-- 
Joseph S. Myers
joseph@codesourcery.com