Improving GMP configure

[Niels Möller]

Torbjorn Granlund <tg at gmplib.org> writes:

> * Add a mechanism for using a default ABI (as already discussed):
>
>    o Choose compiler according to current rules, then figure out that
>      compiler's default ABI.
>
>    o Problem 1: Different compilers might have different default ABIs,
>      which can lead to surprises and still require user's to pass
>      special options.

One of the main points of this feature is that the resulting
library will be compatible with other packages built with default
options. So I'd advocate to let the standard AC_PROG_CC choose the
compiler here (since it seems a bit tricky to detect the default ABI of
that compiler, and then figure out what flags to pass to get a different
compiler to use that same ABI).

Under what circumstances do you want a different compiler than
AC_PROG_CC?

> * When configure promotes a compiler from a generic name like 'cc' to
>   Sun's 'acc' or IBM's xlc, it drops cc_cflags.  This happens e.g., for
>   none-ibm-aix6.1.  (This is probably not hard to fix.)

I'm not following you here. But I'm not very familiar with these
configure features.

>    o Deprecate none-*-* and add an option --disable-assembly.

Makes sense to me. The nettle configure script calls that option
"--disable-assembler"; I don't know English well enough to say which
name is best, but some consitency would be nice. Any other (GNU)
packages that have a configure option liek that?

> * We don't detect and reject hopelessly broken compiler like gcc 4.3.2
>   or the buggy xlc compilers.  Perhaps we should simply detect them,
>   unless somebody can come up with a feature test (that does not require
>   target machine execution).

What type of bugs? If it's miscompilation, and you don't want to execute
any target code, I guess one would have to somehow examine generated
assembler. Sounds possible but tricky to me.



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