Index: libgcc/configure
===================================================================
--- libgcc/configure	(revision 152187)
+++ libgcc/configure	(working copy)
@@ -1918,7 +1918,7 @@
   withval=$with_slibdir; slibdir="$with_slibdir"
 else
   if test "${version_specific_libs}" = yes; then
-  slibdir='$(libsubdir)'
+  slibdir='$(libdir)/gcc/$(host_noncanonical)/$(version)'
 elif test -n "$with_cross_host" && test x"$with_cross_host" != x"no"; then
   slibdir='$(exec_prefix)/$(host_noncanonical)/lib'
 else
Index: libgcc/configure.ac
===================================================================
--- libgcc/configure.ac	(revision 152187)
+++ libgcc/configure.ac	(working copy)
@@ -70,7 +70,7 @@
 [  --with-slibdir=DIR      shared libraries in DIR [LIBDIR]],
 slibdir="$with_slibdir",
 if test "${version_specific_libs}" = yes; then
-  slibdir='$(libsubdir)'
+  slibdir='$(libdir)/gcc/$(host_noncanonical)/$(version)'
 elif test -n "$with_cross_host" && test x"$with_cross_host" != x"no"; then
   slibdir='$(exec_prefix)/$(host_noncanonical)/lib'
 else
Index: libgcc/config/t-slibgcc-darwin
===================================================================
--- libgcc/config/t-slibgcc-darwin	(revision 152187)
+++ libgcc/config/t-slibgcc-darwin	(working copy)
@@ -11,10 +11,19 @@
 SHLIB_DIR = @multilib_dir@
 SHLIB_LC = -lc
 
+ifeq (/usr/lib,$(shlib_slibdir))
+$(warning "Looks like we BUILD stubs, slib install path = $(shlib_slibdir)")
+BUILD_STUBS=1
+else
+$(warning "Looks like we don't BUILD stubs, slib install path = $(shlib_slibdir)")
+BUILD_STUBS=0
+endif
+
 # Darwin only searches in /usr/lib for shared libraries, not in subdirectories,
 # so the libgcc variants have different names not different locations.
 # Note that this version is used for the loader, not the linker; the linker
 # uses the stub versions named by the versioned members of $(INSTALL_FILES).
+
 SHLIB_LINK = $(CC) $(LIBGCC2_CFLAGS) -dynamiclib -nodefaultlibs \
 	-install_name @shlib_slibdir@/$(SHLIB_INSTALL_NAME) \
 	-single_module -o $(SHLIB_DIR)/$(SHLIB_SONAME).tmp \
@@ -26,8 +35,21 @@
 SHLIB_MKMAP_OPTS = -v leading_underscore=1
 SHLIB_MAPFILES += $(gcc_srcdir)/libgcc-std.ver
 
-INSTALL_FILES=libgcc_s.10.4.dylib libgcc_s.10.5.dylib libgcc_s.1.dylib
+LGCC_FILES  = libgcc_s.1.dylib
+ifeq ($(BUILD_STUBS),1)
+LGCC_STUBS = libgcc_s.10.4.dylib libgcc_s.10.5.dylib
+else
+LGCC_STUBS =
+endif
 
+LGCC_FILES += $(LGCC_STUBS)
+
+LEXT_STUBS = libgcc_ext.10.4$(SHLIB_EXT) libgcc_ext.10.5$(SHLIB_EXT)
+
+LGCC_FILES += $(LEXT_STUBS)
+
+INSTALL_FILES=$(LGCC_FILES)
+
 # For the toplevel multilib, build a fat archive including all the multilibs.
 ifeq ($(MULTIBUILDTOP),)
 
@@ -62,8 +84,21 @@
 	$(LIPO) -output $@ -create $(@)_T*
 	rm $(@)_T*
 
-libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT): all-multi libgcc_s$(SHLIB_EXT) \
-	libgcc_s.10.4.dylib libgcc_s.10.5.dylib
+libgcc_ext.%.dylib : $(SHLIB_VERPFX).%.ver libgcc_s$(SHLIB_EXT) all-multi
+	$(STRIP) -o $(@)_T \
+	  -R $(SHLIB_VERPFX).$(*).ver -c -urx \
+	  ./libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT).tmp
+	MLIBS=`$(CC) --print-multi-lib \
+		| sed -e 's/;.*$$//' -e '/^\.$$/d'` ; \
+	for mlib in $$MLIBS ; do \
+	  $(STRIP) -o $(@)_T$${mlib} \
+	    -R $(SHLIB_VERPFX).$(*).ver -c -urx \
+	    ../$${mlib}/libgcc/$${mlib}/libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT).tmp || exit 1 ; \
+	done
+	$(LIPO) -output $@ -create $(@)_T*
+	rm $(@)_T*
+
+libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT): all-multi libgcc_s$(SHLIB_EXT) $(LGCC_STUBS) $(LEXT_STUBS)
 	cp libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT).tmp \
 	  ./libgcc_s.$(SHLIB_SOVERSION)$(SHLIB_EXT)_T_ || exit 1 ; \
 	MLIBS=`$(CC) --print-multi-lib \
Index: gcc/config/darwin.opt
===================================================================
--- gcc/config/darwin.opt	(revision 152187)
+++ gcc/config/darwin.opt	(working copy)
@@ -22,6 +22,10 @@
 Target Report Var(darwin_fix_and_continue)
 Generate code suitable for fast turn around debugging
 
+muse-shared-libgcc-ext
+Target Report Var(darwin_shared_libgcc_ext)
+Use gcc functionality added since the OS release.
+
 ; The Init here is for the convenience of GCC developers, so that
 ; cc1 and cc1plus don't crash if no -mmacosx-version-min is passed.  The
 ; driver will always pass a -mmacosx-version-min, so in normal use
Index: gcc/config/darwin.h
===================================================================
--- gcc/config/darwin.h	(revision 152187)
+++ gcc/config/darwin.h	(working copy)
@@ -391,12 +391,18 @@
 #define REAL_LIBGCC_SPEC						   \
    "%{static-libgcc|static: -lgcc_eh -lgcc;				   \
       shared-libgcc|fexceptions|fgnu-runtime:				   \
-       %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_s.10.4)	   \
-       %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5)	   \
-       -lgcc;								   \
-      :%:version-compare(>< 10.3.9 10.5 mmacosx-version-min= -lgcc_s.10.4) \
-       %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5)	   \
-       -lgcc}"
+       %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_s.10.4 )	   \
+       %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5 )	   \
+       %{muse-shared-libgcc-ext: \
+         %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_ext.10.4)	   \
+         %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_ext.10.5)	   \
+       } -lgcc;								   \
+      :%:version-compare(>< 10.3.9 10.5 mmacosx-version-min= -lgcc_s.10.4 )  \
+       %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_s.10.5 )	   \
+       %{muse-shared-libgcc-ext: \
+         %:version-compare(!> 10.5 mmacosx-version-min= -lgcc_ext.10.4)	   \
+         %:version-compare(>= 10.5 mmacosx-version-min= -lgcc_ext.10.5)	   \
+       } -lgcc } "
 
 /* We specify crt0.o as -lcrt0.o so that ld will search the library path.