Re: ABI incompatibilities with MinGW GCC 4.7.0

[Jason Rumney <jasonr@gnu.org>]

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.

> 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.  If we were using C++, it might be another story, but for
interfaces to third-party libraries that are distributed separately in
binary form, C++ has always been a bad choice.