Re: Overriding cross_compiling when host != build isn't a good enough test

[Daniel Jacobowitz]

On Tue, May 18, 2004 at 12:41:58PM -0700, Daniel Kegel wrote:
> Background:
> Currently, autoconf sets cross_compiling=no if host_alias = build_alias.
> That's not always correct -- if you want to build from pristine sources,
> the best way is to pretend it's a cross-build.  (LFS comes to mind.)
> The usual workaround is to use a slightly phony value for host_alias
> by modifying the more-or-less unused manufacturer field (e.g. 
> i686-HOST-linux-gnu).
> This fails for architectures which only have a single manufacturer,
> as config.sub will reject phony manufacturer names.
> It's also clumsy when doing a canadian cross, as all those phony machine
> names get confusing.
> 
> My current problem:
> I'm doing a canadian cross build of a gcc/glibc toolchain.
> gcc is configured with
>  --build=i686-pc-linux-gnu --target=x86_64-unknown-linux-gnu 
>  --host=x86_64-unknown-linux-gnu
> and glibc is configured with the machine types shifted by one as usual
> (see the famous comment in 
> http://gcc.gnu.org/ml/libstdc++/2003-07/msg00461.html,
> and another example at 
> http://handhelds.org/download/toolchain/gcc-build-cross-3.3):
>  --build=x86_64-unknown-linux-gnu --host=x86_64-unknown-linux-gnu
> Configuring glibc-2.3.2 fails with the error
>   checking size of long double... configure: error: cannot compute sizeof 
>   (long double), 77
> because autoconf-2.57 mistakenly thinks that because build=host, it
> can run the output of the C compiler.

But this is incorrect.  You don't shift by one; you shift target into
host, but build should stay the same.  How can you expect configure to
work right if you lie to it about the build host?

-- 
Daniel Jacobowitz