--enable-fat option doesn't work on Mac OS X / PowerPC

Michael Abshoff Michael.Abshoff at fsmath.mathematik.uni-dortmund.de
Fri Aug 17 13:36:35 CEST 2007

Hello Vincent,

Vincent Lefevre wrote:
> "./configure --help" says:
>   --enable-fat            build a fat binary on systems that support it
>                           [default=no]
> I've tried it under Mac OS X, as Mac OS X supports fat binaries,

Technically fat binaries on Mac OS9 and maybe earlier are binaries with an
68k and a PowerPC personality. MacOSX has universal binaries which combine
32 or 64 bit and PowerPC or x86 (a total of 4 combinations) executables.

If you want to build a universal version of the gmp build them
individually and use lipo to combine the output. For more details see man

> but
> it doesn't seem to work: no dynamic library is generated.

The same happens on Opterons, but as it is stated in the help this only
works on x86.

> The GMP manual says:
> Fat binary, `--enable-fat'
>      Using `--enable-fat' selects a "fat binary" build on x86, where
>      optimized low level subroutines are chosen at runtime according to
>      the CPU detected.  This means more code, but gives good
>      performance on all x86 chips.  (This option might become available
>      for more architectures in the future.)
> So, I suppose that the "configure --help" should be: "build a fat binary
> on x86", and the configure script should fail if --enable-fat is provided
> but does not work.

That would be the right solution.

> --
> Vincent Lefèvre <vincent at vinc17.org> - Web: <http://www.vinc17.org/>
> 100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
> Work: CR INRIA - computer arithmetic / Arenaire project (LIP, ENS-Lyon)



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