# DP: - Disable some biarch libraries for biarch builds.
# DP: - Fix multilib builds on kernels which don't support all multilibs.

Index: b/src/config-ml.in
===================================================================
--- a/src/config-ml.in
+++ b/src/config-ml.in
@@ -467,6 +467,25 @@
 	;;
 esac
 
+if [ -z "$biarch_multidir_names" ]; then
+  biarch_multidir_names="libiberty libstdc++-v3 libgfortran libmudflap libssp libffi libobjc libgomp"
+  echo "WARNING: biarch_multidir_names is unset. Use default value:"
+  echo "  $biarch_multidir_names"
+fi
+ml_srcbase=`basename $ml_realsrcdir`
+old_multidirs="${multidirs}"
+multidirs=""
+for x in ${old_multidirs}; do
+    case " $x " in
+	" 32 "|" n32 "|" x32 "|" 64 "|" hf "|" sf ")
+	case "$biarch_multidir_names" in
+	    *"$ml_srcbase"*) multidirs="${multidirs} ${x}" ;;
+	esac
+	;;
+	*) multidirs="${multidirs} ${x}" ;;
+    esac
+done
+
 # Remove extraneous blanks from multidirs.
 # Tests like `if [ -n "$multidirs" ]' require it.
 multidirs=`echo "$multidirs" | sed -e 's/^[ ][ ]*//' -e 's/[ ][ ]*$//' -e 's/[ ][ ]*/ /g'`
@@ -654,6 +673,35 @@
 
   for ml_dir in ${multidirs}; do
 
+    # a native build fails if the running kernel doesn't support the multilib
+    # variant; force cross compilation for these cases.
+    ml_host_arg=
+    case "${host}" in
+    i[34567]86-*-linux*)
+        case "${ml_dir}" in
+	  64) ml_host_arg="--host=x86_64-linux-gnu";;
+	  x32) ml_host_arg="--host=x86_64-linux-gnux32";;
+	esac
+	;;
+    powerpc-*-linux*)
+	case "${ml_dir}" in
+	  64) ml_host_arg="--host=powerpc64-linux-gnu"
+	esac
+	;;
+    s390-*-linux*)
+	case "${ml_dir}" in
+	  64) ml_host_arg="--host=s390x-linux-gnu"
+	esac
+	;;
+    x86_64-*-linux*)
+	case "${ml_dir}" in
+	  x32) ml_host_arg="--host=x86_64-linux-gnux32"
+	esac
+    esac
+    if [ -n "${ml_host_arg}" ]; then
+       ml_host_arg="${ml_host_arg} --with-default-host-alias=${host_alias}"
+    fi
+
     if [ "${ml_verbose}" = --verbose ]; then
       echo "Running configure in multilib subdir ${ml_dir}"
       echo "pwd: `${PWDCMD-pwd}`"
@@ -858,9 +906,20 @@
 	fi
     fi
 
+    ml_configure_args=
+    for arg in ${ac_configure_args}
+    do
+      case $arg in
+      *CC=*)  ml_configure_args=${ml_config_env} ;;
+      *CXX=*) ml_configure_args=${ml_config_env} ;;
+      *GCJ=*) ml_configure_args=${ml_config_env} ;;
+      *) ;;
+      esac
+    done
+
     if eval ${ml_config_env} ${ml_config_shell} ${ml_recprog} \
 	--with-multisubdir=${ml_dir} --with-multisrctop=${multisrctop} \
-	${ac_configure_args} ${ml_config_env} ${ml_srcdiroption} ; then
+	${ac_configure_args} ${ml_configure_args} ${ml_host_arg} ${ml_srcdiroption} ; then
       true
     else
       exit 1
Index: b/src/libstdc++-v3/include/Makefile.am
===================================================================
--- a/src/libstdc++-v3/include/Makefile.am
+++ b/src/libstdc++-v3/include/Makefile.am
@@ -821,8 +821,9 @@
 endif
 
 host_srcdir = ${glibcxx_srcdir}/$(OS_INC_SRCDIR)
-host_builddir = ./${host_alias}/bits
-host_installdir = ${gxx_include_dir}/${host_alias}$(MULTISUBDIR)/bits
+default_host_alias = @default_host_alias@
+host_builddir = ./${default_host_alias}/bits
+host_installdir = ${gxx_include_dir}/${default_host_alias}$(MULTISUBDIR)/bits
 host_headers = \
 	${host_srcdir}/ctype_base.h \
 	${host_srcdir}/ctype_inline.h \
@@ -1042,6 +1043,7 @@
 
 stamp-${host_alias}:
 	@-mkdir -p ${host_builddir}
+	@test ${default_host_alias} = ${host_alias} || ln -sf ${default_host_alias} ${host_alias}
 	@$(STAMP) stamp-${host_alias}
 
 # Host includes static.
Index: b/src/libstdc++-v3/include/Makefile.in
===================================================================
--- a/src/libstdc++-v3/include/Makefile.in
+++ b/src/libstdc++-v3/include/Makefile.in
@@ -1066,8 +1066,9 @@
 # For --enable-cheaders=c_std
 @GLIBCXX_C_HEADERS_COMPATIBILITY_TRUE@c_compatibility_headers_extra = ${c_compatibility_headers}
 host_srcdir = ${glibcxx_srcdir}/$(OS_INC_SRCDIR)
-host_builddir = ./${host_alias}/bits
-host_installdir = ${gxx_include_dir}/${host_alias}$(MULTISUBDIR)/bits
+default_host_alias = @default_host_alias@
+host_builddir = ./${default_host_alias}/bits
+host_installdir = ${gxx_include_dir}/${default_host_alias}$(MULTISUBDIR)/bits
 host_headers = \
 	${host_srcdir}/ctype_base.h \
 	${host_srcdir}/ctype_inline.h \
@@ -1445,6 +1446,7 @@
 
 stamp-${host_alias}:
 	@-mkdir -p ${host_builddir}
+	@test ${default_host_alias} = ${host_alias} || ln -sf ${default_host_alias} ${host_alias}
 	@$(STAMP) stamp-${host_alias}
 
 # Host includes static.
Index: b/src/libstdc++-v3/configure.ac
===================================================================
--- a/src/libstdc++-v3/configure.ac
+++ b/src/libstdc++-v3/configure.ac
@@ -447,6 +447,16 @@
   multilib_arg=
 fi
 
+AC_ARG_WITH(default-host-alias,
+[AS_HELP_STRING([--with-default-host-alias=TRIPLET],
+                [specifies host triplet used for the default multilib build])],
+[case "${withval}" in
+yes)    AC_MSG_ERROR(bad value ${withval} given for default host triplet) ;;
+no)     default_host_alias='${host_alias}' ;;
+*)      default_host_alias=${withval} ;;
+esac],[default_host_alias='${host_alias}'])
+AC_SUBST(default_host_alias)
+
 # Export all the install information.
 GLIBCXX_EXPORT_INSTALL_INFO