64-bit configure hell

[Ulrich Weigand]

Benjamin Kosnik wrote:

>I think if you search through libstdc++ bugzilla you will find reports
>of oddness with x86_64 systems and the 64 bit multilib. To me, if you
>have to disable multilibs on 32/64 bit systems to get a working
>toolchain, something is wrong.

In my experience, the main problem is that in order to build 32-bit
libraries you need 32-bit development libraries (libc.a, crt*.o)
installed on the system, and many distributions don't install
those by default.  (Or vice versa on systems that use a mostly-32-bit
userland.)

I guess one way to fix this problem would be to only build those
multilibs where the required system dependencies are in fact installed;
this could be verified by attempting to build a 'hello world' using
the multilib flags.  If this already fails, there's no point in
attempting to build the library.

Something like that is actually attempted in config-ml.in, at least
for some platforms.  However this doesn't work, as those checks are
not applied for libgcc (and thus we fail already there).  I think I
pointed this out already some time in the past, and was told that
this is difficult to fix with the current make process ...


Mit freundlichen Gruessen / Best Regards

Ulrich Weigand

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  Dr. Ulrich Weigand
  Linux for S/390 Design & Development
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