Re: ABI incompatibilities with MinGW GCC 4.7.0

[Eli Zaretskii <eliz@gnu.org>]

> From: Jason Rumney <jasonr@gnu.org>
> Cc: Achim Gratz <Stromeko@nexgo.de>,  emacs-devel@gnu.org
> Date: Sat, 09 Jun 2012 22:44:01 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> I still think that simply adding '-mno-ms-bitfields' to the build is all
> >> you need for Emacs
> >
> > If we know the libraries out there are not built with GCC 4.7.x, then
> > this is indeed the way to go.  But what about people who like to build
> > all their libraries themselves? if they use GCC 4.7 to build their
> > libraries, and don't make a point of using '-mno-ms-bitfields' when
> > they do, we cannot let them build Emacs with '-mno-ms-bitfields', can
> > we?
> 
> The GTK binaries available for Windows have been built with
> -mms-bitfields for some years now, and the image libraries contained
> within them have worked without problem with Emacs for all that time. So
> I think the choice of whether to build with or without that flag is a
> non-issue for Emacs.

What is true for some libraries might be false for others.  It all
depends whether a library triggers the code generation where this
switch makes the difference.

> > And then there's the issue of other ABI changes, if there are any.
> > That is the really disturbing part, because the bitfields issue rarely
> > if at all affects real-life code.
> 
> It is somewhat disturbing that the MinGW-GCC maintainers themselves are
> unsure about other ABI changes, but I doubt that any of them will affect
> pure C code except maybe in more rare corner cases like the bitfield
> issue.

A I said, I hope you are right.  But until we _know_ for sure, I think
it's prudent to tell people to stay away of the new version, which was
the sole purpose of my OP.  If you are saying that people can safely
disregard this issue, then I very much disagree.