Re: Obsolete AC_LANG_SAVE/AC_LANG_RESTORE

[Ralf Wildenhues]

Hi Eric,

* Eric Blake wrote on Mon, May 25, 2009 at 02:52:37PM CEST:
> According to Ralf Wildenhues on 5/24/2009 7:52 AM:
> >> libtool 2.2.6a uses AC_LANG_SAVE/AC_LANG_RESTORE in libtool.m4.
> >> These macros have been obsoleted by Autoconf.
> >>
> >> Could they be switched to LANG_PUSH/AC_LANG_POP in future releases?
> > 
> > Not really; I don't think the latter provide equivalent functionality;
> > at least, if memory serves correctly.
> 
> In this case, there is nothing more to AC_LANG_SAVE/AC_LANG_RESTORE than
> thin AU_DEFUN wrappers around AC_LANG_POP.  They provide equivalent
> functionality.

OK, I looked now.  You can call AC_LANG_SAVE/AC_LANG_RESTORE without
arguments, and the restore will do TRT, namely restoring the ac_ext,
ac_compile and ac_link settings that we overwrote in the mean time.

This is useful if the language you are moving to is not defined, such as
Java and Windows Resource.  I don't see how to do it with AC_LANG_PUSH
without argument, or with one not known to Autoconf:

configure.ac:189: error: AC_LANG: unknown language: 
../../../autoconf/lib/autoconf/lang.m4:104: _AC_LANG_SET is expanded from...
../../../autoconf/lib/autoconf/lang.m4:120: AC_LANG_PUSH is expanded from...
libltdl/m4/libtool.m4:6837: _LT_LANG_GCJ_CONFIG is expanded from...
libltdl/m4/libtool.m4:814: _LT_LANG is expanded from...
libltdl/m4/libtool.m4:797: LT_LANG is expanded from...
configure.ac:189: the top level

configure.ac:189: error: AC_LANG: unknown language: Java
../../../autoconf/lib/autoconf/lang.m4:104: _AC_LANG_SET is expanded from...
../../../autoconf/lib/autoconf/lang.m4:120: AC_LANG_PUSH is expanded from...
libltdl/m4/libtool.m4:6837: _LT_LANG_GCJ_CONFIG is expanded from...
libltdl/m4/libtool.m4:814: _LT_LANG is expanded from...
libltdl/m4/libtool.m4:797: LT_LANG is expanded from...
configure.ac:189: the top level

Probably Libtool should define these languages, or Autoconf should?

Thanks,
Ralf