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

[Eli Zaretskii <eliz@gnu.org>]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: 19111@debbugs.gnu.org
> Date: Thu, 20 Nov 2014 17:23:14 +0100
> 
> > OK, but at least let's keep the build/host/target triplet correct.
> > It's not right for us to disregard it when it doesn't fit our needs,
> > because the entire configure script is based on the notion that the
> > triplet is the starting point on which all the rest is based.
> >
> > So, if we want to fix that, let's fix the triplet early on, to specify
> > a i686 build, and let the rest of the script do its job as usual.
> 
> I suspect that you have a point here which I don't entirely grasp.
> 
> Are you thinking on a scenario where the user sets --host/--build on the
> configure script to something that doesn't correlate to the contents of
> $MSYSTEM?

No, I'm trying to follow your suggestion that just "./configure && make"
should DTRT.

> > Besides, I came to a conclusion that I don't understand how your
> > suggestion will work anyway.  AFAICT, you just replace tests based on
> > one wrong string (x86_64-*-*) with another wrong string (MINGW64).
> >
> > Or are you saying that MSYS2 somehow magically does not give $MSYSTEM
> > the value MINGW64 when you configure for a 32-bit build?  If so, how
> > does this magic work?  Because if MSYS2 always sets MSYSTEM=MINGW64,
> > then your suggestion isn't going to work, is it?
> >
> > More generally, how do you tell configure that you want a 32-bit build
> > using MinGW64 toolchain?  That requires some special compiler switches
> > (like -m32 or some such), no?
> 
> We are using $MSYSTEM to special-case MinGW(-w64). $MSYSTEM is MINGW32
> when using the 32 bit toolset and MINGW64 when using the 64 bit toolset.
> That's true for MSYS2/MinGW-w64. I'm not sure if MSYS sets $MSYSTEM to
> MINGW or MINGW32, but any of it should be ok with the patch.
> 
> The -m32 switch is actively discouraged by the MinGW-w64 community and
> the official builds does not support it.
> 
> Does this answer your questions?

Sorry, it doesn't.  You say that $MSYSTEM is set to either MINGW32 or
MINGW64, depending on whether 32-bit or 64-bit toolset is used.  But
how does MSYS2 know which toolset you are going to use to compile a
program?  How do you communicate that to MSYS2?

In any case, what I suggest to do is correct the triplet,
automatically, after uname guesses it, if we find that it is wrong for
"the toolset about to be used", whatever that means.