Re: Compiler characteristics

[Ralf Wildenhues]

* NightStrike wrote on Sun, Sep 06, 2009 at 12:08:23PM CEST:
> How do you test to see if the compiler supports a given option?

You could temporarily add it to CFLAGS and either do a compile or link
test, to find out.  That won't catch (non-GCC) compilers though that
only produce a warning upon unknown flags.

IIRC there are macros in the Autoconf Macro Archive for similar
functionality.

Libtool has internal macros _LT_{COMPILER,LINKER}_OPTION that try to
detect compiler warnings for unknown flags, but such an approach is very
brittle in general.

> Specifically, gcc -municode

You could test $GCC ("yes" if gcc), and then a link test as described
above:

  save_CFLAGS=$CFLAGS
  CFLAGS="$CFLAGS -municode"
  AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
                 [echo works],
                 [echo fails])
  CFLAGS=$save_CFLAGS

More fancily, cache the check, and announce what you're doing:

  AC_CACHE_CHECK([whether $CC accepts -municode],
    [ns_cv_cc__municode],
    [save_CFLAGS=$CFLAGS
     CFLAGS="$CFLAGS -municode"
     AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
                    [ns_cv_cc__municode=yes],
                    [ns_cv_cc__municode=no])
     CFLAGS=$save_CFLAGS
    ])
  if test $ns_cv_cc__municode = yes; then
    some action based on the result ...
  fi

Hope that helps.

Cheers,
Ralf