PATCH RFA: Adjust --enable-build-with-cxx configury

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

This patch adjusts the --enable-build-with-cxx configury as requested by
Joseph Myers.

* When building gcc with --enable-build-with-cxx, if HOST_LIBS is not
  empty, then link with $(CC) rather than $(CXX).  HOST_LIBS will be
  non-empty at various times if configured with --with-host-libstdcxx,
  or --with-stage1-libs, or --with-poststage1-libs.  This permits full
  control over how -lstdc++ is used.

* When building gcc with --enable-build-with-cxx, only set the default
  post-stage1 linker flags if the post-stage1 extra libraries are not
  set.  This change also permits full control over how -lstdc++ is
  used.

* When building gcc with --enable-build-with-cxx, if the post-stage1
  extra libraries are not set, then set the post-stage1 linker flags to
  include -static-libgcc as well as -static-libstdc++.  There is no
  general need for gcc to link dynamically against -lgcc.  Actually we
  might want to consider using that even without
  --enable-build-with-cxx.

Bootstrapped on x86_64-unknown-linux-gnu.  OK for mainline?

Ian


top level ChangeLog:

2009-06-24  Ian Lance Taylor  <iant@google.com>

	* configure.ac: Change default of poststage1_ldflags to be empty if
	poststage1_libs is set.  When poststage1_libs is empty, and
	ENABLE_BUILD_WITH_CXX is set, add -static-libgcc.
	* configure: Rebuild.

gcc/ChangeLog:

2009-06-24  Ian Lance Taylor  <iant@google.com>

	* Makefile.in (HOST_LIBS): Move higher in file.
	(LINKER, LINKER_FLAGS): If ENABLE_BUILD_WITH_CXX, but $(HOST_LIBS)
	is not empty, set to $(CC) and $(CFLAGS).


Index: gcc/Makefile.in
===================================================================
--- gcc/Makefile.in	(revision 148889)
+++ gcc/Makefile.in	(working copy)
@@ -206,6 +206,9 @@ NM = @NM@
 RANLIB = @RANLIB@
 RANLIB_FLAGS = @ranlib_flags@
 
+# Libraries to use on the host.
+HOST_LIBS = @HOST_LIBS@
+
 # The name of the compiler to use.
 ENABLE_BUILD_WITH_CXX = @ENABLE_BUILD_WITH_CXX@
 ifneq ($(ENABLE_BUILD_WITH_CXX),yes)
@@ -216,8 +219,17 @@ LINKER_FLAGS = $(CFLAGS)
 else
 COMPILER = $(CXX)
 COMPILER_FLAGS = $(CXXFLAGS)
+# If HOST_LIBS is set, then the user is controlling the libraries to
+# link against.  In that case, link with $(CC) so that the -lstdc++
+# library is not introduced.  If HOST_LIBS is not set, link with
+# $(CXX) to pick up -lstdc++.
+ifeq ($(HOST_LIBS),)
 LINKER = $(CXX)
 LINKER_FLAGS = $(CXXFLAGS)
+else
+LINKER = $(CC)
+LINKER_FLAGS = $(CFLAGS)
+endif
 endif
 
 # -------------------------------------------
@@ -288,9 +300,6 @@ write_entries_to_file = $(shell rm -f $(
 # In stage2 and beyond, we force this to "-o $@" since we know we're using gcc.
 OUTPUT_OPTION = @OUTPUT_OPTION@
 
-# Libraries to use on the host.
-HOST_LIBS = @HOST_LIBS@
-
 # This is where we get zlib from.  zlibdir is -L../zlib and zlibinc is
 # -I../zlib, unless we were configured with --with-system-zlib, in which
 # case both are empty.
Index: configure.ac
===================================================================
--- configure.ac	(revision 148889)
+++ configure.ac	(working copy)
@@ -1450,21 +1450,6 @@ AC_ARG_WITH(stage1-libs,
 [stage1_libs=$with_host_libstdcxx])
 AC_SUBST(stage1_libs)
 
-# Linker flags to use for stage2 and later builds.
-AC_ARG_WITH(boot-ldflags,
-[  --with-boot-ldflags=FLAGS Linker flags for stage2 and later],
-[if test "$withval" = "no" -o "$withval" = "yes"; then
-   poststage1_ldflags=
- else
-   poststage1_ldflags=$withval
- fi],
-[if test "$ENABLE_BUILD_WITH_CXX" = "yes"; then
-   poststage1_ldflags=-static-libstdc++
- else
-   poststage1_ldflags=
- fi])
-AC_SUBST(poststage1_ldflags)
-
 # Libraries to use for stage2 and later builds.  This defaults to the
 # argument passed to --with-host-libstdcxx.
 AC_ARG_WITH(boot-libs,
@@ -1477,6 +1462,23 @@ AC_ARG_WITH(boot-libs,
 [poststage1_libs=$with_host_libstdcxx])
 AC_SUBST(poststage1_libs)
 
+# Linker flags to use for stage2 and later builds.
+AC_ARG_WITH(boot-ldflags,
+[  --with-boot-ldflags=FLAGS Linker flags for stage2 and later],
+[if test "$withval" = "no" -o "$withval" = "yes"; then
+   poststage1_ldflags=
+ else
+   poststage1_ldflags=$withval
+ fi],
+[poststage1_ldflags=
+ # With --enable-build-with-cxx, default to linking libstdc++ and
+ # libgcc statically.  But if the user explicitly specified the
+ # libraries to use, trust that they are doing what they want.
+ if test "$ENABLE_BUILD_WITH_CXX" = "yes" -a "$poststage1_libs" = ""; then
+   poststage1_ldflags="-static-libstdc++ -static-libgcc"
+ fi])
+AC_SUBST(poststage1_ldflags)
+
 # Check for PPL
 ppl_major_version=0
 ppl_minor_version=10