bug#19111: 25.0.50; 32 bits temacs.exe is linked with wrong image-base when built on 64 bit Windows host

[Óscar Fuentes]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Óscar Fuentes <ofv@wanadoo.es>
>> Cc: 19111@debbugs.gnu.org
>> Date: Wed, 19 Nov 2014 22:27:30 +0100
>> 
>> The problem here is that, without explicitly setting --host/--build,
>> uname is not the right thing for detecting the host/build environment,
>> because uname is a MSYS2 thing, when we are building with a MinGW
>> toolset. So either we stop using uname for MinGW builds (use $MSYSTEM),
>> or document that --host/--build are required.
>
> When you use MinGW64 for building a 32-bit executable, you are in
> effect cross-compiling.  So I think telling users to use an explicit
> "--host/--build" argument is TRT, especially since I don't envision
> many people doing that, except for special-case testing.

When we use the mingw toolset under MSYS{2} we are cross-compiling, as
far as autoconf is concerned. But truth is that Emacs' `configure.ac'
already special-cases MinGW by using $MSYSTEM and not requiring
--host/--build, to hide the cross-compilation and make user's life
simple.

Such special handling of the MSYS/MinGW combo assumes that the target
architecture of the MinGW toolset being used is the same as the MSYS
architecture retrieved by `uname'. Once we have MSYS2 supporting both
i686 and x86_64, and MinGW-w64 also supporting both architectures, the
assumption is broken. I foresee similar problems when building for
MINGW64 on a i686 MSYS2.

> Patches for nt/INSTALL are welcome.

Since we already special-case MinGW on the configure script, and fixing
the problem there only changes how the special case is implemented
without touching new areas, I'll very much prefer to apply the patch
shown on my previous message and keep the nice and simple "configure &&
make" procedure working on all cases.