[lmi] What is --host for a native build? [Was: Compiling takes longer with gcc-4.9.2]

[Greg Chicares]

On 2016-01-19 00:48, Vadim Zeitlin wrote:
> On Mon, 18 Jan 2016 22:36:06 +0000 Greg Chicares <address@hidden> wrote:
> GC> On 2016-01-18 14:32, Vadim Zeitlin wrote:
> GC> > On Mon, 18 Jan 2016 05:04:23 +0000 Greg Chicares <address@hidden> wrote:
[...]
> GC> > GC> >  config_options = \
> GC> > GC> >    --prefix=$(prefix) \
> GC> > GC> >    --build=i686-pc-cygwin \
> GC> > GC> > -  --host=i686-pc-mingw32 \
> GC> > GC> > +  --host=i686-w64-mingw32 \
> GC> > GC> 
> GC> > GC> I had missed that. Got it now.
> GC> > 
> GC> >  To answer your question about why it worked: you must have a MinGW 
> Cygwin
> GC> > cross-compiler installed too, don't you?
> GC> 
> GC> No. I have only what lmi's 'install_cygwin.bat' provides:
> 
>  Thinking more about this, I don't actually know what is the --host option
> value used for if you explicitly redefine the values of all the build tools
> (i.e. AR, CC, CXX, LD, ...). Maybe it actually doesn't matter what it is in
> this case as long as it's different from the "build" string?
> 
> GC> Or is it supposed to disregard an incorrect '--host' specification and
> GC> just DWIM?
> 
>  I don't know. Normally a wrong host value would quickly result in a
> failure because configure wouldn't be able to find a working ${host}-gcc,
> but this doesn't happen in our case, of course...

Okay, we've established that '--host=i686-w64-mingw32' is correct for
Cygwin's MinGW-w64 cross compiler, and that '--host=i686-pc-mingw32',
though wrong on the face of it, does in fact work for that cross
compiler because we fully specify each tool.

Now we want to substitute native MinGW-w64 for the cross compiler;
what should '--host' be now, for configuring wx and wxPdfDoc? Perhaps
it doesn't actually matter: with the native mingw.org compiler,
'--host=i686-pc-mingw32' has been working just fine for seven years,
since this change to the way we build wx:
  http://svn.savannah.nongnu.org/viewvc?view=rev&root=lmi&revision=4423
  Configure with '--build=i686-pc-cygwin --host=i686-pc-mingw32'
and it worked just fine in prior years without '--host'. MinGW-w64
native provides prefixed copies of some of its tools, e.g.:
  i686-w64-mingw32-gcc.exe
(but not all--there's no prefixed preprocessor, e.g.), which seems
to suggest that '--host=i686-w64-mingw32', which is in HEAD now,
is the best choice. I suppose it doesn't matter; I don't plan to
change it unless it becomes necessary.