Re: [build, ada] Allow Solaris bootstrap with C++ (PR bootstrap/49794)

[Ian Lance Taylor <iant at google dot com>]

"Ralf Wildenhues" <Ralf.Wildenhues@gmx.de> writes:

> Hello,
>
> * Ian Lance Taylor wrote on Wed, Jul 20, 2011 at 08:06:51PM CEST:
>> Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:
>> 
>> > diff --git a/gcc/configure.ac b/gcc/configure.ac
>> > --- a/gcc/configure.ac
>> > +++ b/gcc/configure.ac
>> > @@ -1041,7 +1041,16 @@ case "${host}" in
>> >  esac
>> >  AC_FUNC_FORK
>> >  
>> > +# FIXME: g++ on Solaris 10+ defines _XOPEN_SOURCE=600, which exposes a
>> > +# different iconv() prototype.
>> > +if test "$ENABLE_BUILD_WITH_CXX" = "yes"; then
>> > +AC_LANG_PUSH([C++])
>> > +fi
>> >  AM_ICONV
>> > +if test "$ENABLE_BUILD_WITH_CXX" = "yes"; then
>> > +AC_LANG_POP([C++])
>> > +fi
>> 
>> I believe that this kind of conditional use of AC_LANG_PUSH/AC_LANG_POP
>> does not work correctly.  The autoconf macros don't play well with the
>> shell conditionals.  We're going to need a different approach.  (That
>> problem is why I didn't do this long ago--I had a similar patch for a
>> while, but I had to take it out.)
>
> I think something like this should work:
>
> AS_IF([test "$ENABLE_BUILD_WITH_CXX" = "yes"],
>   [AC_LANG_PUSH([C++])
>    AM_ICONV
>    AC_LANG_POP([C++])],
>   [AM_ICONV])
>
> Rationale for using AS_IF rather than plain 'if' is that any macros
> required by AM_ICONV will get pulled out to before the AS_IF.  If they
> also need to be run with C++ enabled, then we need to wrap the second
> argument of AS_IF into a separate macro.  Untested, but please complain
> if it doesn't work.

Cool.

In general, though, we should ideally be using C++ when appropriate for
most or all of the compilation tests, not just for AM_ICONV.

Ian