ABI defaults

Niels Möller nisse at lysator.liu.se
Wed Nov 17 18:52:03 CET 2010

Torbjorn Granlund <tg at gmplib.org> writes:

> We need to establish a compiler before we can make any sort of detection
> of the "default ABI", since the default ABI is per compiler.

Sure. So with the ABI=default feature, passing CC="gcc -m64" and
ABI=default would be a different way to get about the same effect as
passing ABI=64.

> We currently try compilers until we find one that supports the best ABI.

I'd be tempted to rip out the logic to select the best ABI completely; I
suspect it is more confusing then helpful to users if gmp is clever when
selecting the ABI. I'd prefer to just display a warning message for poor
ABIs, something like

  You're building GMP for the 32-bit ABI, which gives poor performance
  on this platform. You will get much better performance if you build
  GMP (as well as applications using it) for the 64-bit ABI. To do
  this, pass the ... flag to GMP's configure, and the ... flags to the
  compiler when building applications.


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