Configure fails on 32-bit platform

[Niels Möller]

Vincent Lefevre <vincent at vinc17.net> writes:

> So, in case of 32-bit x86 mode in the compiler, shouldn't $host be
> seen as matching X86_PATTERN instead of X86_64_PATTERN?

Interestingly, it seems config.guess checks $CC (but not $CFLAGS):

  $ ./config.guess 
  haswell-pc-linux-gnu
  $ CC='gcc -m32' ./config.guess 
  x86_64-pc-linux-gnu

If it had produced

  i386-pc-linux-gnu

in the latter case, ABI=64 would probably have been excluded.

GMP configure might like to know both that the compiler is only capable
of 32-bit code, and that the chip is a haswell to be used in 32-bit
mode, not any random x86.

But the thing with GMP configure is that it wants 64-bit code if
possible, so given a compiler which defaults to 32-bit code but is
capable of 64-bit, it wants to use ABI=64 and add -m64 or similar to
CFLAGS. Which gives better performance, but sometimes a bit surprising
to the user. I think it would be better to not automatically add -m64 in
this case, but just display a loud message suggesting a reconfigure with
CC='gcc -m64'.

Regards,
/Niels

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