Re: ABI incompatibilities with MinGW GCC 4.7.0

[Achim Gratz <Stromeko@nexgo.de>]

Eli Zaretskii writes:
> See http://sourceforge.net/mailarchive/message.php?msg_id=29376223 and
> the following discussion (which is still unfolding) for the details.

The first of these is a red herring.  You always needed to know whether
all libraries you link to were produced with '-mms-bitfields' or
'-mno-ms-bitfields' anyway ever since that option was introduced.  So
the default changes with 4.7.0, but you can just as easily chose the
former default.

The second change only affects C++ programs AFAICS and it makes
(__thiscall) the default which has been introduced with 4.6.2 (I think).
I can only assume that you can still override it with (__stdcall), but
that means changes to the source.  There is a disturbing lack of
consideration for backwards compatibility and I would have expected that
the ABI version is bumped (so one could specify the old default with,
say, -mabi=...).  If there's really no way to get the old default back
without qualifying all functions in the source, I'd consider that a
defect that needs to be fixed for 4.7.1.

> (Actually, you cannot safely use the MinGW GCC 4.7.0 for building
> Emacs on Windows at all for now, because (a) there's no MinGW runtime
> available that is compatible with the new ABI, and (b) you must link
> with libxpm.dll, which was compiled by an older GCC.)

I still think that simply adding '-mno-ms-bitfields' to the build is all
you need for Emacs


Regards,
Achim.
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