diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 67e5b893f24d8486d87080438648f90881b9ddb7..923708f8a38b99faf2ce203ff67ea7539c6ae28d 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,13 @@
+2012-01-27  Benjamin Kosnik  <bkoz@redhat.com>
+	    Matthias Klose  <doko@ubuntu.com>
+
+	* configure.ac (GLIBCXX_ENABLE_DEBUG_FLAGS): Use -gdwarf-4 -g3 -O0.
+	* configure.in: Regenerated.
+	* src/Makefile.am (all-once, install-data-once): New rules.
+	(all-local, install-data-local): Use them.
+	(build-debug, install-debug): Tweak.
+	* src/Makefile.in: Regenerate.
+
 2012-01-27  Richard Henderson  <rth@redhat.com>
 
 	* include/bits/atomic_base.h (__atomic_flag_base): Define _M_i
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 51ecfd6536fa26c9efd20d56672108997483a3dd..5c1c4bbe639788c7add585a47bee7aedc18c9aa6 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -1534,7 +1534,7 @@ Optional Features:
   --enable-concept-checks use Boost-derived template checks [default=no]
   --enable-libstdcxx-debug-flags=FLAGS
                           pass compiler FLAGS when building debug library
-                          [default="-g3 -O0"]
+                          [default="-gdwarf-4 -g3 -O0"]
   --enable-libstdcxx-debug
                           build extra debug library [default=no]
   --enable-cxx-flags=FLAGS
@@ -17096,7 +17096,7 @@ if test "${enable_libstdcxx_debug_flags+set}" = set; then :
       *)          as_fn_error "--enable-libstdcxx-debug-flags needs compiler flags as arguments" "$LINENO" 5 ;;
      esac
 else
-  enable_libstdcxx_debug_flags="-g3 -O0"
+  enable_libstdcxx_debug_flags="-gdwarf-4 -g3 -O0"
 fi
 
 
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index c5f79011f1c54284051f992f080c30e379e4069a..7607e5b732e7f352584fe5c9c4ea0faf7c5cbe12 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -124,7 +124,7 @@ GLIBCXX_ENABLE_LONG_LONG([yes])
 GLIBCXX_ENABLE_WCHAR_T([yes])
 GLIBCXX_ENABLE_C99([yes])
 GLIBCXX_ENABLE_CONCEPT_CHECKS([no])
-GLIBCXX_ENABLE_DEBUG_FLAGS(["-g3 -O0"])
+GLIBCXX_ENABLE_DEBUG_FLAGS(["-gdwarf-4 -g3 -O0"])
 GLIBCXX_ENABLE_DEBUG([no])
 GLIBCXX_ENABLE_PARALLEL([yes])
 GLIBCXX_ENABLE_CXX_FLAGS
diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
index 87b2a1682d73ccbdf2173a37b917dfcc3bab488b..2cd27749fa66579ce6f92489ee5b16e8d79d5385 100644
--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -168,16 +168,16 @@ version_arg =
 version_dep =
 endif
 
-# Added rules.
-# 1 debug library
-# 2 supra-convenience library
-if GLIBCXX_BUILD_DEBUG
-all-local: libstdc++convenience.la build_debug
-install-data-local: install_debug
-else
-all-local: libstdc++convenience.la
-install-data-local:
-endif
+
+# Control additional build primary rules.
+# EXTRA_LTLIBRARIES =
+all-once: libstdc++convenience.la $(STAMP_DEBUG)
+install-data-once: $(STAMP_INSTALL_DEBUG)
+
+all-local: all-once
+install-data-local: install-data-once
+clean-local:
+	rm -rf libstdc++convenience.la stamp* $(CLEAN_DEBUG)
 
 # Make a non-installed convenience library, so that --disable-static
 # may work.
@@ -188,13 +188,26 @@ libstdc++convenience.la: $(toolexeclib_LTLIBRARIES)
 	fi; \
 	echo `date` > stamp-libstdc++convenience;
 
-debugdir = debug
+# Added rules.
+# 1 debug library
+# 2 supra-convenience library
+if GLIBCXX_BUILD_DEBUG
+STAMP_DEBUG = build-debug
+STAMP_INSTALL_DEBUG = install-debug
+CLEAN_DEBUG = debug
+else
+STAMP_DEBUG =
+STAMP_INSTALL_DEBUG =
+CLEAN_DEBUG =
+endif
 
-# Build a set of debug objects here.
+# Build a debug variant.
 # Take care to fix all possibly-relative paths.
+debugdir = ${glibcxx_builddir}/src/debug
 stamp-debug:
 	if test ! -d ${debugdir}; then \
 	  mkdir -p ${debugdir}; \
+	  for d in $(SUBDIRS); do mkdir -p  ${debugdir}/$$d; done; \
 	  (cd ${debugdir}; \
 	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
 	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
@@ -202,16 +215,30 @@ stamp-debug:
 	      -e 's/VPATH = \.\./VPATH = ..\/../' \
 	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
 	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	      -e 's/all-local: build_debug/all-local:/' \
-	      -e 's/install-data-local: install_debug/install-data-local:/' \
-	  < ../Makefile > Makefile) ; \
+	  < ../Makefile > Makefile ; \
+	  for d in . $(SUBDIRS); do \
+	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
+	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
+	      -e 's/srcdir = \.\./srcdir = ..\/../' \
+	      -e 's/VPATH = \.\./VPATH = ..\/../' \
+	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
+	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
+	  < ../$$d/Makefile > $$d/Makefile ; \
+	  done) ; \
 	fi; \
 	echo `date` > stamp-debug;
 
-build_debug: stamp-debug
-	(cd ${debugdir} && $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' all)
-
-# Install debug library here.
-install_debug:
-	(cd ${debugdir} && $(MAKE) \
-	toolexeclibdir=$(glibcxx_toolexeclibdir)/debug install)
+build-debug: stamp-debug
+	  (cd ${debugdir}; \
+	  mv Makefile Makefile.tmp; \
+	  sed -e 's,all-local: all-once,all-local:,' \
+	      -e 's,install-data-local: install-data-once,install-data-local:,' \
+	      -e 's,src/c,src/debug/c,' \
+	  < Makefile.tmp > Makefile ; \
+	  $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
+	  toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all) ;
+
+# Install debug library.
+install-debug: build-debug
+	(cd ${debugdir} && $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
+	toolexeclibdir=$(glibcxx_toolexeclibdir)/debug install) ;
diff --git a/libstdc++-v3/src/Makefile.in b/libstdc++-v3/src/Makefile.in
index 11ee8ba721eb12bca94a1e0b6cbe467f5e662297..79340a2c7fd6e6b22f1ccce7142d94bd17059a71 100644
--- a/libstdc++-v3/src/Makefile.in
+++ b/libstdc++-v3/src/Makefile.in
@@ -405,7 +405,20 @@ CXXLINK = $(LIBTOOL) --tag CXX $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=link \
 @ENABLE_SYMVERS_GNU_TRUE@@ENABLE_SYMVERS_SOL2_FALSE@@ENABLE_SYMVERS_TRUE@version_dep = libstdc++-symbols.ver
 @ENABLE_SYMVERS_GNU_TRUE@@ENABLE_SYMVERS_SOL2_TRUE@@ENABLE_SYMVERS_TRUE@version_dep = libstdc++-symbols.ver-sol2
 @ENABLE_SYMVERS_SUN_TRUE@@ENABLE_SYMVERS_TRUE@version_dep = libstdc++-symbols.ver-sun
-debugdir = debug
+@GLIBCXX_BUILD_DEBUG_FALSE@STAMP_DEBUG = 
+
+# Added rules.
+# 1 debug library
+# 2 supra-convenience library
+@GLIBCXX_BUILD_DEBUG_TRUE@STAMP_DEBUG = build-debug
+@GLIBCXX_BUILD_DEBUG_FALSE@STAMP_INSTALL_DEBUG = 
+@GLIBCXX_BUILD_DEBUG_TRUE@STAMP_INSTALL_DEBUG = install-debug
+@GLIBCXX_BUILD_DEBUG_FALSE@CLEAN_DEBUG = 
+@GLIBCXX_BUILD_DEBUG_TRUE@CLEAN_DEBUG = debug
+
+# Build a debug variant.
+# Take care to fix all possibly-relative paths.
+debugdir = ${glibcxx_builddir}/src/debug
 all: all-recursive
 
 .SUFFIXES:
@@ -655,8 +668,8 @@ maintainer-clean-generic:
 	@echo "it deletes files that may require special tools to rebuild."
 clean: clean-recursive
 
-clean-am: clean-generic clean-libtool clean-toolexeclibLTLIBRARIES \
-	mostlyclean-am
+clean-am: clean-generic clean-libtool clean-local \
+	clean-toolexeclibLTLIBRARIES mostlyclean-am
 
 distclean: distclean-recursive
 	-rm -f Makefile
@@ -727,7 +740,7 @@ uninstall-am: uninstall-toolexeclibLTLIBRARIES
 
 .PHONY: $(RECURSIVE_CLEAN_TARGETS) $(RECURSIVE_TARGETS) CTAGS GTAGS \
 	all all-am all-local check check-am clean clean-generic \
-	clean-libtool clean-toolexeclibLTLIBRARIES ctags \
+	clean-libtool clean-local clean-toolexeclibLTLIBRARIES ctags \
 	ctags-recursive distclean distclean-compile distclean-generic \
 	distclean-libtool distclean-tags dvi dvi-am html html-am info \
 	info-am install install-am install-data install-data-am \
@@ -785,13 +798,15 @@ vpath % $(top_srcdir)
 @ENABLE_SYMVERS_DARWIN_TRUE@@ENABLE_SYMVERS_TRUE@	    sed 's,/\([^/.]*\)\.la,/.libs/\1.a,g'` \
 @ENABLE_SYMVERS_DARWIN_TRUE@@ENABLE_SYMVERS_TRUE@	 > $@ || (rm -f $@ ; exit 1)
 
-# Added rules.
-# 1 debug library
-# 2 supra-convenience library
-@GLIBCXX_BUILD_DEBUG_TRUE@all-local: libstdc++convenience.la build_debug
-@GLIBCXX_BUILD_DEBUG_TRUE@install-data-local: install_debug
-@GLIBCXX_BUILD_DEBUG_FALSE@all-local: libstdc++convenience.la
-@GLIBCXX_BUILD_DEBUG_FALSE@install-data-local:
+# Control additional build primary rules.
+# EXTRA_LTLIBRARIES =
+all-once: libstdc++convenience.la $(STAMP_DEBUG)
+install-data-once: $(STAMP_INSTALL_DEBUG)
+
+all-local: all-once
+install-data-local: install-data-once
+clean-local:
+	rm -rf libstdc++convenience.la stamp* $(CLEAN_DEBUG)
 
 # Make a non-installed convenience library, so that --disable-static
 # may work.
@@ -801,12 +816,10 @@ libstdc++convenience.la: $(toolexeclib_LTLIBRARIES)
 	  cp .libs/libstdc++convenience.a .libs/libstdc++.a; \
 	fi; \
 	echo `date` > stamp-libstdc++convenience;
-
-# Build a set of debug objects here.
-# Take care to fix all possibly-relative paths.
 stamp-debug:
 	if test ! -d ${debugdir}; then \
 	  mkdir -p ${debugdir}; \
+	  for d in $(SUBDIRS); do mkdir -p  ${debugdir}/$$d; done; \
 	  (cd ${debugdir}; \
 	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
 	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
@@ -814,19 +827,33 @@ stamp-debug:
 	      -e 's/VPATH = \.\./VPATH = ..\/../' \
 	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
 	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
-	      -e 's/all-local: build_debug/all-local:/' \
-	      -e 's/install-data-local: install_debug/install-data-local:/' \
-	  < ../Makefile > Makefile) ; \
+	  < ../Makefile > Makefile ; \
+	  for d in . $(SUBDIRS); do \
+	  sed -e 's/top_builddir = \.\./top_builddir = ..\/../' \
+	      -e 's/top_build_prefix = \.\./top_build_prefix = ..\/../' \
+	      -e 's/srcdir = \.\./srcdir = ..\/../' \
+	      -e 's/VPATH = \.\./VPATH = ..\/../' \
+	      -e 's/glibcxx_basedir = \.\./glibcxx_basedir = ..\/../' \
+	      -e 's/MKDIR_P = \.\./MKDIR_P = ..\/../' \
+	  < ../$$d/Makefile > $$d/Makefile ; \
+	  done) ; \
 	fi; \
 	echo `date` > stamp-debug;
 
-build_debug: stamp-debug
-	(cd ${debugdir} && $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' all)
-
-# Install debug library here.
-install_debug:
-	(cd ${debugdir} && $(MAKE) \
-	toolexeclibdir=$(glibcxx_toolexeclibdir)/debug install)
+build-debug: stamp-debug
+	  (cd ${debugdir}; \
+	  mv Makefile Makefile.tmp; \
+	  sed -e 's,all-local: all-once,all-local:,' \
+	      -e 's,install-data-local: install-data-once,install-data-local:,' \
+	      -e 's,src/c,src/debug/c,' \
+	  < Makefile.tmp > Makefile ; \
+	  $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
+	  toolexeclibdir=$(glibcxx_toolexeclibdir)/debug all) ;
+
+# Install debug library.
+install-debug: build-debug
+	(cd ${debugdir} && $(MAKE) CXXFLAGS='$(DEBUG_FLAGS)' \
+	toolexeclibdir=$(glibcxx_toolexeclibdir)/debug install) ;
 
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.