Re: Problem with Sun Studio 12 C++

[Eric Blake]

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[revisiting an old thread]

According to Ralf Wildenhues on 3/9/2009 12:28 PM:

Hi Ralf, others,

>>> The cpp-works stuff is necessary for systems without a working C++
>>> compiler.  AC_PROG_CXX sets CXX to g++ in that case.  We should find
>>> out why that was done, and fix it.
>> Didn't libtool already have to hack around that fact?  Yes, it would be
>> nice to make autoconf more honest when CXX cannot be found, but as a
>> separate patch.
> 
> yes and yes and yes.

I'm not sure why it was done, but this appears to fix it.  I'm in the
middle of testing a libtool bootstrap after (temporarily) removing my C++
compiler; if everything still works, are there any objections to this patch?

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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>From 5f22e075cbae3331ed1d7ed56d4ed63117238425 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Sat, 6 Jun 2009 11:24:26 -0600
Subject: [PATCH] Avoid ambiguous fallback in AC_PROG_CXX, AC_PROG_OBJC.

* lib/autoconf/c.m4 (AC_PROG_CXX, AC_PROG_OBJC): Use 'no', rather
than an ambiguous compiler name, when no compiler is present.
Reported by Ralf Wildenhues and others.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog         |    5 +++++
 NEWS              |    6 ++++++
 lib/autoconf/c.m4 |    4 ++--
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 45cc4b4..9a7ccf7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2009-06-06  Eric Blake  <address@hidden>

+       Avoid ambiguous fallback in AC_PROG_CXX, AC_PROG_OBJC.
+       * lib/autoconf/c.m4 (AC_PROG_CXX, AC_PROG_OBJC): Use 'no', rather
+       than an ambiguous compiler name, when no compiler is present.
+       Reported by Ralf Wildenhues and others.
+
        Document fallback behavior of AC_PROG_LEX.
        * doc/autoconf.texi (Particular Programs) <AC_PROG_LEX>: Mention
        why fallback is :, and that a --version check must be used to
diff --git a/NEWS b/NEWS
index 82ba635..060c34b 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,12 @@ GNU Autoconf NEWS - User visible changes.
 * Major changes in Autoconf 2.64 (2009-??-??) [stable]
   Released by Eric Blake, based on git versions 2.63b.*.

+** AC_PROG_CXX and AC_PROG_OBJC now set CXX/OBCJ to "no" instead
+   of "g++"/"gcc" when no compiler for the requested language is
+   present on the user's machine.  This change was made to accomodate
+   packages that perform conditional compilation based on the presence
+   of a language, such as Libtool.
+
 ** AS_IF and AS_CASE have been taught to avoid syntax errors even when
    given arguments that expand to just whitespace.

diff --git a/lib/autoconf/c.m4 b/lib/autoconf/c.m4
index ffdbd45..1bdc9af 100644
--- a/lib/autoconf/c.m4
+++ b/lib/autoconf/c.m4
@@ -699,7 +699,7 @@ if test -z "$CXX"; then
     AC_CHECK_TOOLS(CXX,
                   [m4_default([$1],
                               [g++ c++ gpp aCC CC cxx cc++ cl.exe FCC KCC RCC 
xlC_r xlC])],
-                  g++)
+                  no)
   fi
 fi
 # Provide some information about the compiler.
@@ -871,7 +871,7 @@ _AC_ARG_VAR_CPPFLAGS()dnl
 _AC_ARG_VAR_PRECIOUS([OBJC])dnl
 AC_CHECK_TOOLS(OBJC,
               [m4_default([$1], [gcc objcc objc cc CC])],
-              gcc)
+              no)
 # Provide some information about the compiler.
 _AS_ECHO_LOG([checking for _AC_LANG compiler version])
 set X $ac_compile
-- 
1.6.3.rc3.2.g4b51