Adding configure flag

[Aurelio Remonda <aurelio dot remonda at tallertechnologies dot com>]

Hi, im trying to add a configure flag to the libstdc++ for a feature
I'm testing. This flag, if enabled, would define a C macro that I'd be
using in new-opnt.cc.

I was doing some research and i believe i need to edit configure.ac
and acinclude.m4 on the libstdc++-v3 directory. Is this correct?

I also need to run autoconf to regenerate the libstdc++-v3 configure
script, right?

Do i need to make changes on the configure.ac file in the top gcc
directory? Or can i create the flag and do the configure and make on
the libstdc++-v3 directory so it's ready for when I compile all of
gcc?

On a related subject: right now, I've added the following line to the
libstdc++v3's configure.ac:

GLIBCXX_ENABLE_NEW_OPNT_IF([no])

Also, I added the following to libstdc++v3's acinclude.m4:

AC_DEFUN([GLIBCXX_ENABLE_NEW_OPNT_IF], [
  GLIBCXX_ENABLE(new-opnt-if,$1,,[enable if on new_opnt instead of while])
  if test $enable_new_opnt_if = yes; then
    AC_DEFINE(_GLIBCXX_NEW_OPNT_IF, 1,
        [Define is new_opnt will be used instead of while.])
  fi
  AC_MSG_CHECKING([for enabled if])
  AC_MSG_RESULT([$enable_new_opnt_if])
])

And on gcc top directory configure.ac:
[AS_HELP_STRING([--enable-new-opnt-if],
    [enable if on new_opnt instead of while])],
[], [enable_new_opnt_if=yes])
AC_SUBST(enable_multilib)

As you can see, I've hardcoded this option as "yes" to test it.
However, I can't seem to make it work: in new-opnt.cc, I still can't
see the macro defined. Am I doing something wrong?

Thanks a lot!

-- 
Aurelio Remonda

Software Engineer

San Lorenzo 47, 3rd Floor, Office 5
CÃrdoba, Argentina
Phone: +54-351-4217888 / 4218211