[patch] Change valid arguments for --with-default-libstdcxx-abi

[Jonathan Wakely <jwakely at redhat dot com>]

I intend to commit this to trunk and the gcc-5-branch either today or
tomorrow.

I made a mistake in using "c++98" and "c++11" as the valid arguments
for the ABI configure option, because it confuses people into thinking
that it is affected by, or affects, the -std=c++11 option.  In fact
the ABI mode and -std standard mode are independent.

The inline namespace is called __cxx11, the ABI-tag is "cxx11" and the
controlling macro is _GLIBCXX_USE_CXX11_ABI so I think referring to
the ABI as "cxx11" might help distinguish it from the -std=c++11 mode.

This will require distros that are using the
--with-default-libstdcxx-abi option to change their build scripts,
because using c++98 (or similar) now gives an error:

checking for default std::string ABI to use... configure: error: Supported arguments for --with-default-libstdcxx-abi have changed, use "cxx11" or "cxx98"
Makefile:11390: recipe for target 'configure-target-libstdc++-v3' failed

commit 6baea9aaba16ee07e0ad2a190ec9c2a2d6f5648c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jul 1 14:22:05 2015 +0100

    	* acinclude.m4 (GLIBCXX_DEFAULT_ABI): Change valid arguments for
    	--with-default-libstdcxx-abi
    	* configure: Regenerate.
    	* doc/xml/manual/configure.xml: Document valid arguments.

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 8340572..df71a08 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -3792,7 +3792,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_DUAL_ABI], [
   fi
   if test x"$enable_libstdcxx_dual_abi" != xyes; then
     AC_MSG_NOTICE([dual ABI is disabled])
-    default_libstdcxx_abi="c++98"
+    default_libstdcxx_abi="cxx98"
   fi
   GLIBCXX_CONDITIONAL(ENABLE_DUAL_ABI, test $enable_libstdcxx_dual_abi = yes)
 ])
@@ -3800,7 +3800,7 @@ AC_DEFUN([GLIBCXX_ENABLE_LIBSTDCXX_DUAL_ABI], [
 dnl
 dnl Check to see which ABI should be enabled by default.
 dnl
-dnl --with-default-libstdcxx-abi={c++98,c++11}
+dnl --with-default-libstdcxx-abi={cxx98,cxx11}
 dnl
 dnl Defines:
 dnl  _GLIBCXX_USE_CXX11_ABI (always defined, either to 1 or 0)
@@ -3812,14 +3812,16 @@ AC_DEFUN([GLIBCXX_DEFAULT_ABI], [
     AS_HELP_STRING([--with-default-libstdcxx-abi],
                    [set the std::string ABI to use by default]),
     [case "$withval" in
-      c++98|gnu++98|c++03|gnu++03)  default_libstdcxx_abi="c++98" ;;
-      c++1?|gnu++1?)  default_libstdcxx_abi="c++11" ;;
+      cxx98)  default_libstdcxx_abi="cxx98" ;;
+      cxx11)  default_libstdcxx_abi="cxx11" ;;
+      c++*|gnu++*) AC_MSG_ERROR([Supported arguments for --with-default-libstdcxx-abi have changed, use "cxx11" or "cxx98"]) ;;
       *)  AC_MSG_ERROR([Invalid argument for --with-default-libstdcxx-abi]) ;;
-     esac],
-    [default_libstdcxx_abi="c++11"])
+     esac
+     ],
+    [default_libstdcxx_abi="cxx11"])
   AC_MSG_RESULT(${default_libstdcxx_abi})
   fi
-  if test $default_libstdcxx_abi = "c++11"; then
+  if test $default_libstdcxx_abi = "cxx11"; then
     glibcxx_cxx11_abi=1
     glibcxx_cxx98_abi=0
   else
diff --git a/libstdc++-v3/doc/xml/manual/configure.xml b/libstdc++-v3/doc/xml/manual/configure.xml
index 9ba9c1a..40d7138 100644
--- a/libstdc++-v3/doc/xml/manual/configure.xml
+++ b/libstdc++-v3/doc/xml/manual/configure.xml
@@ -389,9 +389,9 @@
    <para>
      Set the default value for the <symbol>_GLIBCXX_USE_CXX11_ABI</symbol>
      macro (see <xref linkend="manual.intro.using.macros"/>).
-     The default is <option>OPTION=c++11</option> which sets the macro to
+     The default is <option>OPTION=cxx11</option> which sets the macro to
      <literal>1</literal>,
-     use <option>OPTION=c++98</option> to set it to <literal>0</literal>.
+     use <option>OPTION=cxx98</option> to set it to <literal>0</literal>.
      This option does not change the library ABI.
    </para>
  </listitem></varlistentry>