Re: AC_*/AM_* macros for options

[Rhys Ulerich]

> I think there would need to be a higher-level "abstract"
> know (low, medium, high), and then a way to add specific
> compiler-specific options for specific circumstances.
>
> Something like:
> AC_PROG_CC_WARNINGS_ADD([clang], 
> [-Wtautological-constant-out-of-range-compare -Wpointer-sign 
> -Wformat-extra-args]

As someone mentioned before, the autoconf-archive has several very
nice building blocks.  AX_APPEND_COMPILE_FLAGS [1] adds flags to
CFLAGS (or, if you like, CFLAGS_{LOW,MED,HIGH}) if the current
language compiler accepts them.  AC_COMPILER_VENDOR [2] permits
detecting compilers, much like the clang example you gave above.
These can be put together in a project-specific macro to slice and
dice warnings however you desire.  Following the lead of the FFTW
guys, I have an example of such an "assembly" AC_DEFUN in one of my
projects [3].

It would not be hard to either (a) rewrite your hypothetical
AC_PROG_CC_WARNINGS_ADD in terms of these (along with some
AC_LANG_PUSH and AC_LANG_POP love) or to (b) implement it with these
building blocks.

The autoconf-archive is quite a nice collection of tools.  If you've
got suggested low/medium/high flag wishlists that you care to
implement, by all means please open up a feature on Savannah with an
attached patch.

[1] http://www.gnu.org/software/autoconf-archive/ax_append_compile_flags
[2] http://www.gnu.org/software/autoconf-archive/ax_compiler_vendor
[3] https://github.com/RhysU/suzerain/blob/master/m4/ax_warnings_sanitize.m4

- Rhys