Re: [ping] Re: [patch v2] support for multiarch systems

[Matthias Klose <doko at ubuntu dot com>]

Am 02.11.2012 18:37, schrieb Ian Lance Taylor:
> On Fri, Nov 2, 2012 at 6:26 AM, Matthias Klose <doko@ubuntu.com> wrote:
> > > +ifeq ($(enable_multiarch),yes)
> > > +  if_multiarch = $(1)
> > > +else ifeq ($(enable_multiarch),auto-detect)
> > > +  if_multiarch = $(if $(wildcard $(shell echo
> > > $(SYSTEM_HEADER_DIR))/../../usr/lib/*/crti.o),$(1))
> > > +else
> > > +  if_multiarch =
> > > +endif
> > >
> > > This is nicely tricky but I don't understand why you are doing this in
> > > such a confusing way.  Why not simply set the names in config.gcc?
> > > What information do you have at make time that you don't have at
> > > configure time?
> >
> >
> > this is for the auto case. SYSTEM_HEADER_DIR is not accessible/available
> > from
> > config.gcc. This is the same approach as taken for MULTILIB_OSDDIRNAMES.
> > Also setting the names for the multiarch directories in the same place as
> > done for for the MULTILIB_OSDIRNAMES seems to be better choice.
>
> SYSTEM_HEADER_DIR is available in gcc/configure.ac, and you could do
> the $(if $(wildcard $(shell echo
> > > $(SYSTEM_HEADER_DIR))/../../usr/lib/*/crti.o) there.  I can't see any reason to do it at make time rather than configure time.

in the thread starting at 
http://gcc.gnu.org/ml/gcc-patches/2007-09/msg00696.html it was suggested to use 
this construct.

SYSTEM_HEADER_DIR is in Makefile syntax, and cannot be evaluated in 
configure.ac.  Now you could add a SYSTEM_HEADER_DIR_sh variable to track the 
same configuration in shell syntax, but this seems to be error prone to 
maintain. Plus the Makefile has the comment for this macro saying "to be 
overridden by targets".

For now, I added a comment in the Makefile.in, why SYSTEM_HEADER_DIR cannot be 
used in configure.ac.

> > +	      if (*q2 == ':')
> > +		end = q2;
>
> Don't reuse end here.  Use a new variable.

done.

> Please update the comment for set_multilib_dir.  It's not a very good
> comment, but it does describe the syntax, and you seem to be changing
> the syntax.

added:
  A subdirectory name is optionally followed by a colon and the corresponding
  multiarch name.

> > -      if (this_path[0] == '.' && this_path[1] == ':')
> > +      if (this_path[0] == '.' && this_path[1] == ':' && this_path[2] != ':')
>
> The existing comment here is reasonably clear.  Please update the
> comment to show why this change is correct.

updated comment:
      /* When --disable-multilib was used but target defines
         MULTILIB_OSDIRNAMES, entries starting with .: (and not starting
         with .:: for multiarch configurations) are there just to find
         multilib_os_dir, so skip them from output.  */

> > +Specify wether to enable or disable multiarch support.  The default is
>
> s/wether/whether/
>
> > +to detect for glibc start files in a multiarch location, and enable it
>
> s/detect/check/ or something along those lines.

done.

now testing the attached patch.

  Matthias

2012-11-04  Matthias Klose  <doko@ubuntu.com>

	* doc/invoke.texi: Document -print-multiarch.
	* doc/install.texi: Document --enable-multiarch.
	* doc/fragments.texi: Document MULTILIB_OSDIRNAMES, MULTIARCH_DIRNAME.
	* configure.ac: Add --enable-multiarch option.
	* configure: Regenerate.
	* Makefile.in (s-mlib): Pass MULTIARCH_DIRNAME to genmultilib.
	enable_multiarch, with_float: New macros.
	if_multiarch: New macro, define in terms of enable_multiarch.
	* genmultilib: Add new argument for the multiarch name.
	* gcc.c (multiarch_dir): Define.
	(for_each_path): Search for multiarch suffixes.
	(driver_handle_option): Handle multiarch option.
	(do_spec_1): Pass -imultiarch if defined.
	(main): Print multiarch.
	(set_multilib_dir): Separate multilib and multiarch names
	from multilib_select.
	(print_multilib_info): Ignore multiarch names in multilib_select.
	* incpath.c (add_standard_paths): Search the multiarch include dirs.
	* cppdefault.h (default_include): Document multiarch in multilib
	member.
	* cppdefault.c: [LOCAL_INCLUDE_DIR, STANDARD_INCLUDE_DIR] Add an
        include directory for multiarch directories.
	* common.opt: New options --print-multiarch and -imultilib.
	* config.gcc <i[34567]86-*-linux* | x86_64-*-linux*> (tmake_file):
	Include i386/t-linux.
	<i[34567]86-*-kfreebsd*-gnu | x86_64-*-kfreebsd*-gnu> (tmake_file):
	Include i386/t-kfreebsd.
	<i[34567]86-*-gnu*> (tmake_file): Include i386/t-gnu.
	* config/i386/t-linux64: Add multiarch names in
	MULTILIB_OSDIRNAMES, define MULTIARCH_DIRNAME.
	* config/i386/t-gnu: New file.
	* config/i386/t-kfreebsd: Likewise.
	* config/i386/t-linux: Likewise.


Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 193133)
+++ doc/invoke.texi	(working copy)
@@ -6309,6 +6309,11 @@
 @file{../lib32}, or if OS libraries are present in @file{lib/@var{subdir}}
 subdirectories it prints e.g.@: @file{amd64}, @file{sparcv9} or @file{ev6}.
 
+@item -print-multiarch
+@opindex print-multiarch
+Print the path to OS libraries for the selected multiarch,
+relative to some @file{lib} subdirectory.
+
 @item -print-prog-name=@var{program}
 @opindex print-prog-name
 Like @option{-print-file-name}, but searches for a program such as @samp{cpp}.
Index: doc/install.texi
===================================================================
--- doc/install.texi	(revision 193133)
+++ doc/install.texi	(working copy)
@@ -1033,6 +1033,15 @@
 conventions, etc.@: should not be built.  The default is to build a
 predefined set of them.
 
+@item --enable-multiarch
+Specify whether to enable or disable multiarch support.  The default is
+to check for glibc start files in a multiarch location, and enable it
+if the files are found.  The auto detection is enabled for native builds,
+and for cross builds configured with @option{--with-sysroot}, and without
+@option{--with-native-system-header-dir}.
+More documentation about multiarch can be found at
+@uref{http://wiki.debian.org/Multiarch}.
+
 Some targets provide finer-grained control over which multilibs are built
 (e.g., @option{--disable-softfloat}):
 @table @code
Index: doc/fragments.texi
===================================================================
--- doc/fragments.texi	(revision 193133)
+++ doc/fragments.texi	(working copy)
@@ -93,6 +93,12 @@
 default value will be @code{MULTILIB_OPTIONS}, with all slashes treated
 as spaces.
 
+@code{MULTILIB_DIRNAMES} describes the multilib directories using GCC
+conventions and is applied to directories that are part of the GCC
+installation.  When multilib-enabled, the compiler will add a
+subdirectory of the form @var{prefix}/@var{multilib} before each
+directory in the search path for libraries and crt files.
+
 For example, if @code{MULTILIB_OPTIONS} is set to @samp{m68000/m68020
 msoft-float}, then the default value of @code{MULTILIB_DIRNAMES} is
 @samp{m68000 m68020 msoft-float}.  You may specify a different value if
@@ -152,6 +158,60 @@
 of options to be used for all builds.  If you set this, you should
 probably set @code{CRTSTUFF_T_CFLAGS} to a dash followed by it.
 
+@findex MULTILIB_OSDIRNAMES
+@item MULTILIB_OSDIRNAMES
+If @code{MULTILIB_OPTIONS} is used, this variable specifies 
+a list of subdirectory names, that are used to modify the search
+path depending on the chosen multilib.  Unlike @code{MULTILIB_DIRNAMES},
+@code{MULTILIB_OSDIRNAMES} describes the multilib directories using
+operating systems conventions, and is applied to the directories such as
+@code{lib} or those in the @env{LIBRARY_PATH} environment variable.
+The format is either the same as of
+@code{MULTILIB_DIRNAMES}, or a set of mappings.  When it is the same
+as @code{MULTILIB_DIRNAMES}, it describes the multilib directories
+using operating system conventions, rather than GCC conventions.  When it is a set
+of mappings of the form @var{gccdir}=@var{osdir}, the left side gives
+the GCC convention and the right gives the equivalent OS defined
+location.  If the @var{osdir} part begins with a @samp{!},
+GCC will not search in the non-multilib directory and use
+exclusively the multilib directory.  Otherwise, the compiler will
+examine the search path for libraries and crt files twice; the first
+time it will add @var{multilib} to each directory in the search path,
+the second it will not.
+
+For configurations that support both multilib and multiarch,
+@code{MULTILIB_OSDIRNAMES} also encodes the multiarch name, thus
+subsuming @code{MULTIARCH_DIRNAME}.  The multiarch name is appended to
+each directory name, separated by a colon (e.g.
+@samp{../lib32:i386-linux-gnu}).
+
+Each multiarch subdirectory will be searched before the corresponding OS
+multilib directory, for example @samp{/lib/i386-linux-gnu} before
+@samp{/lib/../lib32}.  The multiarch name will also be used to modify the
+system header search path, as explained for @code{MULTIARCH_DIRNAME}.
+
+@findex MULTIARCH_DIRNAME
+@item MULTIARCH_DIRNAME
+This variable specifies the multiarch name for configurations that are
+multiarch-enabled but not multilibbed configurations.
+
+The multiarch name is used to augment the search path for libraries, crt
+files and system header files with additional locations.  The compiler
+will add a multiarch subdirectory of the form
+@var{prefix}/@var{multiarch} before each directory in the library and
+crt search path.  It will also add two directories
+@code{LOCAL_INCLUDE_DIR}/@var{multiarch} and
+@code{NATIVE_SYSTEM_HEADER_DIR}/@var{multiarch}) to the system header
+search path, respectively before @code{LOCAL_INCLUDE_DIR} and
+@code{NATIVE_SYSTEM_HEADER_DIR}.
+
+@code{MULTIARCH_DIRNAME} is not used for configurations that support
+both multilib and multiarch.  In that case, multiarch names are encoded
+in @code{MULTILIB_OSDIRNAMES} instead.
+
+More documentation about multiarch can be found at
+@uref{http://wiki.debian.org/Multiarch}.
+
 @findex SPECS
 @item SPECS
 Unfortunately, setting @code{MULTILIB_EXTRA_OPTS} is not enough, since
Index: common.opt
===================================================================
--- common.opt	(revision 193133)
+++ common.opt	(working copy)
@@ -348,6 +348,9 @@
 -print-multi-os-directory
 Driver Alias(print-multi-os-directory)
 
+-print-multiarch
+Driver Alias(print-multiarch)
+
 -print-prog-name
 Driver Separate Alias(print-prog-name=)
 
@@ -2353,6 +2356,10 @@
 Common Joined Var(plugindir_string) Init(0)
 -iplugindir=<dir>	Set <dir> to be the default plugin directory
 
+imultiarch
+Common Joined Separate RejectDriver Var(imultiarch) Init(0)
+-imultiarch <dir>	Set <dir> to be the multiarch include subdirectory
+
 l
 Driver Joined Separate
 
@@ -2409,6 +2416,9 @@
 
 print-multi-os-directory
 Driver Var(print_multi_os_directory)
+ 
+print-multiarch
+Driver Var(print_multiarch)
 
 print-prog-name=
 Driver JoinedOrMissing Var(print_prog_name)
Index: config.gcc
===================================================================
--- config.gcc	(revision 193133)
+++ config.gcc	(working copy)
@@ -3640,10 +3640,15 @@
 
 	i[34567]86-*-darwin* | x86_64-*-darwin*)
 		;;
-	i[34567]86-*-linux* | x86_64-*-linux* | \
-	  i[34567]86-*-kfreebsd*-gnu | x86_64-*-kfreebsd*-gnu | \
-	  i[34567]86-*-gnu*)
+	i[34567]86-*-linux* | x86_64-*-linux*)
+		tmake_file="$tmake_file i386/t-linux"
 		;;
+	i[34567]86-*-kfreebsd*-gnu | x86_64-*-kfreebsd*-gnu)
+		tmake_file="$tmake_file i386/t-kfreebsd"
+		;;
+	i[34567]86-*-gnu*)
+		tmake_file="$tmake_file i386/t-gnu"
+		;;
 	i[34567]86-*-solaris2* | x86_64-*-solaris2.1[0-9]*)
 		;;
 	i[34567]86-*-cygwin* | i[34567]86-*-mingw* | x86_64-*-mingw*)
Index: configure.ac
===================================================================
--- configure.ac	(revision 193133)
+++ configure.ac	(working copy)
@@ -613,6 +613,31 @@
 [], [enable_multilib=yes])
 AC_SUBST(enable_multilib)
 
+# Determine whether or not multiarch is enabled.
+AC_ARG_ENABLE(multiarch,
+[AS_HELP_STRING([--enable-multiarch],
+		[enable support for multiarch paths])],
+[case "${withval}" in
+yes|no|auto) enable_multiarch=$withval;;
+*) AC_MSG_ERROR(bad value ${withval} given for --enable-multiarch option) ;;
+esac], [enable_multiarch=auto])
+if test x${enable_multiarch} = xauto; then
+  if test x${with_native_system_header_dir} != x; then
+    ma_msg_suffix=", disabled auto check (configured with --native-system-header-dir)"
+    enable_multiarch=no
+  fi
+  if test x$host != x$target && test "x$with_sysroot" = x; then
+    ma_msg_suffix=", disabled auto check (cross build configured without --with-sysroot)"
+    enable_multiarch=no
+  fi
+fi
+AC_MSG_CHECKING(for multiarch configuration)
+AC_SUBST(enable_multiarch)
+AC_MSG_RESULT($enable_multiarch$ma_msg_suffix)
+
+# needed for setting the multiarch name for soft-float/hard-float ABIs
+AC_SUBST(with_float)
+
 # Enable __cxa_atexit for C++.
 AC_ARG_ENABLE(__cxa_atexit,
 [AS_HELP_STRING([--enable-__cxa_atexit], [enable __cxa_atexit for C++])],
Index: cppdefault.c
===================================================================
--- cppdefault.c	(revision 193133)
+++ cppdefault.c	(working copy)
@@ -63,6 +63,7 @@
 #endif
 #ifdef LOCAL_INCLUDE_DIR
     /* /usr/local/include comes before the fixincluded header files.  */
+    { LOCAL_INCLUDE_DIR, 0, 0, 1, 1, 2 },
     { LOCAL_INCLUDE_DIR, 0, 0, 1, 1, 0 },
 #endif
 #ifdef PREFIX_INCLUDE_DIR
@@ -90,6 +91,7 @@
 #endif
 #ifdef NATIVE_SYSTEM_HEADER_DIR
     /* /usr/include comes dead last.  */
+    { NATIVE_SYSTEM_HEADER_DIR, NATIVE_SYSTEM_HEADER_COMPONENT, 0, 0, 1, 2 },
     { NATIVE_SYSTEM_HEADER_DIR, NATIVE_SYSTEM_HEADER_COMPONENT, 0, 0, 1, 0 },
 #endif
     { 0, 0, 0, 0, 0, 0 }
Index: cppdefault.h
===================================================================
--- cppdefault.h	(revision 193133)
+++ cppdefault.h	(working copy)
@@ -43,9 +43,11 @@
 				   C++.  */
   const char add_sysroot;	/* FNAME should be prefixed by
 				   cpp_SYSROOT.  */
-  const char multilib;		/* FNAME should have the multilib path
-				   specified with -imultilib
-				   appended.  */
+  const char multilib;		/* FNAME should have appended
+				   - the multilib path specified with -imultilib
+				     when 1 is passed,
+				   - the multiarch path specified with
+				     -imultiarch, when 2 is passed.  */
 };
 
 extern const struct default_include cpp_include_defaults[];
Index: incpath.c
===================================================================
--- incpath.c	(revision 193133)
+++ incpath.c	(working copy)
@@ -150,8 +150,14 @@
 	      if (!filename_ncmp (p->fname, cpp_GCC_INCLUDE_DIR, len))
 		{
 		  char *str = concat (iprefix, p->fname + len, NULL);
-		  if (p->multilib && imultilib)
+		  if (p->multilib == 1 && imultilib)
 		    str = concat (str, dir_separator_str, imultilib, NULL);
+		  else if (p->multilib == 2)
+		    {
+		      if (!imultiarch)
+			continue;
+		      str = concat (str, dir_separator_str, imultiarch, NULL);
+		    }
 		  add_path (str, SYSTEM, p->cxx_aware, false);
 		}
 	    }
@@ -203,8 +209,14 @@
 	  else
 	    str = update_path (p->fname, p->component);
 
-	  if (p->multilib && imultilib)
+	  if (p->multilib == 1 && imultilib)
 	    str = concat (str, dir_separator_str, imultilib, NULL);
+	  else if (p->multilib == 2)
+	    {
+	      if (!imultiarch)
+		continue;
+	      str = concat (str, dir_separator_str, imultiarch, NULL);
+	    }
 
 	  add_path (str, SYSTEM, p->cxx_aware, false);
 	}
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 193133)
+++ Makefile.in	(working copy)
@@ -530,6 +530,18 @@
 extra_opt_files=@extra_opt_files@
 host_hook_obj=@out_host_hook_obj@
 
+# Multiarch support
+enable_multiarch = @enable_multiarch@
+with_float = @with_float@
+ifeq ($(enable_multiarch),yes)
+  if_multiarch = $(1)
+else ifeq ($(enable_multiarch),auto)
+  # SYSTEM_HEADER_DIR is makefile syntax, cannot be evaluated in configure.ac
+  if_multiarch = $(if $(wildcard $(shell echo $(SYSTEM_HEADER_DIR))/../../usr/lib/*/crti.o),$(1))
+else
+  if_multiarch =
+endif
+
 # ------------------------
 # Installation directories
 # ------------------------
@@ -1807,10 +1819,11 @@
 	    "$(MULTILIB_EXCLUSIONS)" \
 	    "$(MULTILIB_OSDIRNAMES)" \
 	    "$(MULTILIB_REQUIRED)" \
+	    "$(MULTIARCH_DIRNAME)" \
 	    "@enable_multilib@" \
 	    > tmp-mlib.h; \
 	else \
-	  $(SHELL) $(srcdir)/genmultilib '' '' '' '' '' '' '' '' no\
+	  $(SHELL) $(srcdir)/genmultilib '' '' '' '' '' '' '' '' "$(MULTIARCH_DIRNAME)" no \
 	    > tmp-mlib.h; \
 	fi
 	$(SHELL) $(srcdir)/../move-if-change tmp-mlib.h multilib.h
Index: config/i386/t-kfreebsd
===================================================================
--- config/i386/t-kfreebsd	(revision 0)
+++ config/i386/t-kfreebsd	(revision 0)
@@ -0,0 +1,5 @@
+MULTIARCH_DIRNAME = $(call if_multiarch,i386-kfreebsd-gnu)
+
+# MULTILIB_OSDIRNAMES are set in t-linux64.
+KFREEBSD_OS = $(filter kfreebsd%, $(word 3, $(subst -, ,$(target))))
+MULTILIB_OSDIRNAMES := $(subst linux,$(KFREEBSD_OS),$(MULTILIB_OSDIRNAMES))
Index: config/i386/t-linux64
===================================================================
--- config/i386/t-linux64	(revision 193133)
+++ config/i386/t-linux64	(working copy)
@@ -34,6 +34,6 @@
 comma=,
 MULTILIB_OPTIONS    = $(subst $(comma),/,$(TM_MULTILIB_CONFIG))
 MULTILIB_DIRNAMES   = $(patsubst m%, %, $(subst /, ,$(MULTILIB_OPTIONS)))
-MULTILIB_OSDIRNAMES = m64=../lib64
-MULTILIB_OSDIRNAMES+= m32=$(if $(wildcard $(shell echo $(SYSTEM_HEADER_DIR))/../../usr/lib32),../lib32,../lib)
-MULTILIB_OSDIRNAMES+= mx32=../libx32
+MULTILIB_OSDIRNAMES = m64=../lib64$(call if_multiarch,:x86_64-linux-gnu)
+MULTILIB_OSDIRNAMES+= m32=$(if $(wildcard $(shell echo $(SYSTEM_HEADER_DIR))/../../usr/lib32),../lib32,../lib)$(call if_multiarch,:i386-linux-gnu)
+MULTILIB_OSDIRNAMES+= mx32=../libx32$(call if_multiarch,:x32-linux-gnu)
Index: config/i386/t-linux
===================================================================
--- config/i386/t-linux	(revision 0)
+++ config/i386/t-linux	(revision 0)
@@ -0,0 +1 @@
+MULTIARCH_DIRNAME = $(call if_multiarch,i386-linux-gnu)
Index: config/i386/t-gnu
===================================================================
--- config/i386/t-gnu	(revision 0)
+++ config/i386/t-gnu	(revision 0)
@@ -0,0 +1 @@
+MULTIARCH_DIRNAME = $(call if_multiarch,i386-gnu)
Index: gcc.c
===================================================================
--- gcc.c	(revision 193133)
+++ gcc.c	(working copy)
@@ -1154,6 +1154,11 @@
    set_multilib_dir based on the compilation options.  */
 
 static const char *multilib_os_dir;
+
+/* Subdirectory to use for locating libraries in multiarch conventions.  Set by
+   set_multilib_dir based on the compilation options.  */
+
+static const char *multiarch_dir;
 
 /* Structure to keep track of the specs that have been defined so far.
    These are accessed using %(specname) in a compiler or link
@@ -2084,6 +2089,7 @@
   struct prefix_list *pl;
   const char *multi_dir = NULL;
   const char *multi_os_dir = NULL;
+  const char *multiarch_suffix = NULL;
   const char *multi_suffix;
   const char *just_multi_suffix;
   char *path = NULL;
@@ -2101,11 +2107,14 @@
     }
   if (do_multi && multilib_os_dir && strcmp (multilib_os_dir, ".") != 0)
     multi_os_dir = concat (multilib_os_dir, dir_separator_str, NULL);
+  if (multiarch_dir)
+    multiarch_suffix = concat (multiarch_dir, dir_separator_str, NULL);
 
   while (1)
     {
       size_t multi_dir_len = 0;
       size_t multi_os_dir_len = 0;
+      size_t multiarch_len = 0;
       size_t suffix_len;
       size_t just_suffix_len;
       size_t len;
@@ -2114,16 +2123,15 @@
 	multi_dir_len = strlen (multi_dir);
       if (multi_os_dir)
 	multi_os_dir_len = strlen (multi_os_dir);
+      if (multiarch_suffix)
+	multiarch_len = strlen (multiarch_suffix);
       suffix_len = strlen (multi_suffix);
       just_suffix_len = strlen (just_multi_suffix);
 
       if (path == NULL)
 	{
 	  len = paths->max_len + extra_space + 1;
-	  if (suffix_len > multi_os_dir_len)
-	    len += suffix_len;
-	  else
-	    len += multi_os_dir_len;
+	  len += MAX (MAX (suffix_len, multi_os_dir_len), multiarch_len);
 	  path = XNEWVEC (char, len);
 	}
 
@@ -2152,6 +2160,16 @@
 		break;
 	    }
 
+	  /* Now try the multiarch path.  */
+	  if (!skip_multi_dir
+	      && !pl->require_machine_suffix && multiarch_dir)
+	    {
+	      memcpy (path + len, multiarch_suffix, multiarch_len + 1);
+	      ret = callback (path, callback_info);
+	      if (ret)
+		break;
+	    }
+
 	  /* Now try the base path.  */
 	  if (!pl->require_machine_suffix
 	      && !(pl->os_multilib ? skip_multi_os_dir : skip_multi_dir))
@@ -2980,6 +2998,9 @@
   fputs (_("  -print-libgcc-file-name  Display the name of the compiler's companion library\n"), stdout);
   fputs (_("  -print-file-name=<lib>   Display the full path to library <lib>\n"), stdout);
   fputs (_("  -print-prog-name=<prog>  Display the full path to compiler component <prog>\n"), stdout);
+  fputs (_("\
+  -print-multiarch         Display the target's normalized GNU triplet, used as\n\
+                           a component in the library path\n"), stdout);
   fputs (_("  -print-multi-directory   Display the root directory for versions of libgcc\n"), stdout);
   fputs (_("\
   -print-multi-lib         Display the mapping between command line options and\n\
@@ -3264,6 +3285,7 @@
     case OPT_print_multi_directory:
     case OPT_print_sysroot:
     case OPT_print_multi_os_directory:
+    case OPT_print_multiarch:
     case OPT_print_sysroot_headers_suffix:
     case OPT_time:
     case OPT_wrapper:
@@ -4920,6 +4942,15 @@
 		  do_spec_1 (" ", 0, NULL);
 		}
 
+	      if (multiarch_dir)
+		{
+		  do_spec_1 ("-imultiarch", 1, NULL);
+		  /* Make this a separate argument.  */
+		  do_spec_1 (" ", 0, NULL);
+		  do_spec_1 (multiarch_dir, 1, NULL);
+		  do_spec_1 (" ", 0, NULL);
+		}
+
 	      if (gcc_exec_prefix)
 		{
 		  do_spec_1 ("-iprefix", 1, NULL);
@@ -6589,6 +6620,15 @@
       return (0);
     }
 
+  if (print_multiarch)
+    {
+      if (multiarch_dir == NULL)
+	printf ("\n");
+      else
+	printf ("%s\n", multiarch_dir);
+      return (0);
+    }
+
   if (print_sysroot)
     {
       if (target_system_root)
@@ -7360,7 +7400,9 @@
    options are present, then we will ignore this completely. Passing
    that, gcc will consider each multilib_select in turn using the same
    rules for matching the options. If a match is found, that subdirectory
-   will be used.  */
+   will be used.
+   A subdirectory name is optionally followed by a colon and the corresponding
+   multiarch name.  */
 
 static void
 set_multilib_dir (void)
@@ -7572,10 +7614,25 @@
 	    q++;
 	  if (q < end)
 	    {
-	      char *new_multilib_os_dir = XNEWVEC (char, end - q);
-	      memcpy (new_multilib_os_dir, q + 1, end - q - 1);
-	      new_multilib_os_dir[end - q - 1] = '\0';
-	      multilib_os_dir = new_multilib_os_dir;
+	      const char *q2 = q + 1, *ml_end = end;
+	      char *new_multilib_os_dir;
+
+	      while (q2 < end && *q2 != ':')
+		q2++;
+	      if (*q2 == ':')
+		ml_end = q2;
+	      new_multilib_os_dir = XNEWVEC (char, ml_end - q);
+	      memcpy (new_multilib_os_dir, q + 1, ml_end - q - 1);
+	      new_multilib_os_dir[ml_end - q - 1] = '\0';
+	      multilib_os_dir = *new_multilib_os_dir ? new_multilib_os_dir : ".";
+
+	      if (q2 < end && *q2 == ':')
+		{
+		  char *new_multiarch_dir = XNEWVEC (char, end - q2);
+		  memcpy (new_multiarch_dir, q2 + 1, end - q2 - 1);
+		  new_multiarch_dir[end - q2 - 1] = '\0';
+		  multiarch_dir = new_multiarch_dir;
+		}
 	      break;
 	    }
 	}
@@ -7635,9 +7692,10 @@
 	}
 
       /* When --disable-multilib was used but target defines
-	 MULTILIB_OSDIRNAMES, entries starting with .: are there just
-	 to find multilib_os_dir, so skip them from output.  */
-      if (this_path[0] == '.' && this_path[1] == ':')
+	 MULTILIB_OSDIRNAMES, entries starting with .: (and not starting
+         with .:: for multiarch configurations) are there just to find
+         multilib_os_dir, so skip them from output.  */
+      if (this_path[0] == '.' && this_path[1] == ':' && this_path[2] != ':')
 	skip = 1;
 
       /* Check for matches with the multilib_exclusions. We don't bother
Index: genmultilib
===================================================================
--- genmultilib	(revision 193133)
+++ genmultilib	(working copy)
@@ -84,6 +84,8 @@
 # This argument can be used together with MULTILIB_EXCEPTIONS and will take
 # effect after the MULTILIB_EXCEPTIONS.
 
+# The optional ninth argument is the multiarch name.
+
 # The last option should be "yes" if multilibs are enabled.  If it is not
 # "yes", all GCC multilib dir names will be ".".
 
@@ -133,7 +135,8 @@
 exclusions=$6
 osdirnames=$7
 multilib_required=$8
-enable_multilib=$9
+multiarch=$9
+enable_multilib=${10}
 
 echo "static const char *const multilib_raw[] = {"
 
@@ -261,6 +264,9 @@
 # names.
 toosdirnames=
 defaultosdirname=
+if [ -n "${multiarch}" ]; then
+  defaultosdirname=::${multiarch}
+fi
 if [ -n "${osdirnames}" ]; then
   set x ${osdirnames}
   shift
@@ -268,6 +274,9 @@
     case "$1" in
       .=*)
         defaultosdirname=`echo $1 | sed 's|^.=|:|'`
+	if [ -n "${multiarch}" ]; then
+	  defaultosdirname=${defaultosdirname}:${multiarch}
+	fi
 	shift
 	;;
       *=*)
@@ -353,13 +362,13 @@
     dirout=`echo ${combo} | sed -e 's/=/-/g'`
   fi
   # Remove the leading and trailing slashes.
-  dirout=`echo ${dirout} | sed -e 's|^/||' -e 's|/$||g'`
+  dirout=`echo ${dirout} | sed -e 's|^/||' -e 's|/*:/*|:|' -e 's|/$||g'`
 
   # Use the OS directory names rather than the option names.
   if [ -n "${toosdirnames}" ]; then
     osdirout=`echo ${combo} | sed ${toosdirnames}`
     # Remove the leading and trailing slashes.
-    osdirout=`echo ${osdirout} | sed -e 's|^/||' -e 's|/$||g'`
+    osdirout=`echo ${osdirout} | sed -e 's|^/||' -e 's|/*:/*|:|' -e 's|/$||g'`
     if [ "x${enable_multilib}" != xyes ]; then
       dirout=".:${osdirout}"
       disable_multilib=yes