I would like to propose this patch as a step toward building gcc using a
C++ compiler.  This patch builds stage1 with the C compiler as usual,
and defaults to building stages 2 and 3 with a C++ compiler built during
stage 1.  This means that the gcc installed and used by most people will
be built by a C++ compiler.  This will ensure that gcc is fully
buildable with C++, while retaining the ability to bootstrap with only a
C compiler, not a C++ compiler.  This will permit us to experiment with
optionally using C++ for some code, using a #ifdef to select the C
implementation or the C++ implementation.

I would suggest that we consider releasing 4.7 this way, as a small
trial for building gcc with C++.

This is a big step, so I am sending the patch to both gcc@ and
gcc-patches@ for comments.

Bootstrapped and ran testsuite on x86_64-unknown-linux-gnu.

Ian


2011-07-15  Ian Lance Taylor  <iant@google.com>

	* configure.ac: Add --enable-build-poststage1-with-cxx.  If set,
	make C++ a boot_language.  Set and substitute
	POSTSTAGE1_CONFIGURE_FLAGS.
	* Makefile.tpl (POSTSTAGE1_CONFIGURE_FLAGS): New variable.
	(STAGE[+id+]_CONFIGURE_FLAGS): Add $(POSTSTAGE1_CONFIGURE_FLAGS).
	* configure, Makefile.in: Rebuild.