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

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Submitter Matthias Klose
Date Aug. 7, 2012, 10:31 a.m.
Message ID <5020EE69.4020102@ubuntu.com>
Download mbox | patch
Permalink /patch/175577/
State New
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Comments

Matthias Klose - Aug. 7, 2012, 10:31 a.m.
ping?

re-attaching the updated patch with the fixed comment in genmultilib.

  Matthias

On 08.07.2012 20:48, Matthias Klose wrote:
> Please find attached v2 of the patch updated for trunk 20120706, x86 only, tested on
> x86-linux-gnu, KFreeBSD and the Hurd.
> 
> I left in the comment about the multiarch names, but I'm fine to change/discard
> it. It was first required by Joseph Myers, then not found necessary by Paolo
> Bonzini. The patch includes the changes suggested by Thomas Schwinge.
> 
> Ok for the trunk?
> 
>   Matthias
>
2012-06-25  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.in: 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.
	* cppdeault.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.
Ian Taylor - Aug. 7, 2012, 2:07 p.m.
On Tue, Aug 7, 2012 at 3:31 AM, Matthias Klose <doko@ubuntu.com> wrote:
> ping?
>
> On 08.07.2012 20:48, Matthias Klose wrote:
>> Please find attached v2 of the patch updated for trunk 20120706, x86 only, tested on
>> x86-linux-gnu, KFreeBSD and the Hurd.

> +[case "${withval}" in
> +yes|no|auto-detect) enable_multiarch=$withval;;
> +*) AC_MSG_ERROR(bad value ${withval} given for --enable-multiarch option) ;;

Please just use "auto", not "auto-detect", as in libgcc/configure.ac.

> +# needed for setting the multiarch name on ARM
> +AC_SUBST(with_float)

This seems like it should be in a different patch.

> +with_float = @with_float@

Likewise.

+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?

The auto case is not general.  When cross-compiling without --sysroot,
or when using --native-system-header-dir, the test won't work.
Without --sysroot there may not be much that you can do to auto-detect
multiarch.  And with --sysroot, there should be no need to use
SYSTEM_HEADER_DIR at all; just look in the sysroot.

> +@item --enable-multiarch
> +Specify wether to enable or disable multiarch support.  The default is
> +to detect for glibc start files in a multiarch location, and enable it
> +if the files are found.

This is quite obscure for anybody who does not already know what multiarch is.

I'm sorry, I have to repeat my extreme annoyance that this scheme
breaks all earlier GCC releases.

Ian
Eric Botcazou - Nov. 15, 2012, 11:41 a.m.
> re-attaching the updated patch with the fixed comment in genmultilib.

This has introduced:

make[3]: Leaving directory `/red.a/gnatmail/gcc-x/build-red/x86_64-
linux/gnat/obj/libdecnumber'
make[3]: Entering directory `/red.a/gnatmail/gcc-x/build-red/x86_64-
linux/gnat/obj/gcc'
Makefile:538: Extraneous text after `else' directive
Makefile:541: *** only one `else' per conditional.  Stop.


# Multiarch support
enable_multiarch = auto
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

Patch

Index: configure.ac
===================================================================
--- configure.ac	(revision 188931)
+++ configure.ac	(working copy)
@@ -623,6 +623,21 @@ 
 [], [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 "${withval}" in
+yes|no|auto-detect) enable_multiarch=$withval;;
+*) AC_MSG_ERROR(bad value ${withval} given for --enable-multiarch option) ;;
+esac], [enable_multiarch=auto-detect])
+AC_MSG_CHECKING(for multiarch configuration)
+AC_SUBST(enable_multiarch)
+AC_MSG_RESULT($enable_multiarch)
+
+# needed for setting the multiarch name on ARM
+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 188931)
+++ 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 188931)
+++ 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: Makefile.in
===================================================================
--- Makefile.in	(revision 188931)
+++ Makefile.in	(working copy)
@@ -350,6 +350,17 @@ 
 
 enable_plugin = @enable_plugin@
 
+# Multiarch support
+enable_multiarch = @enable_multiarch@
+with_float = @with_float@
+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
+
 CPPLIB = ../libcpp/libcpp.a
 CPPINC = -I$(srcdir)/../libcpp/include
 
@@ -1845,10 +1856,11 @@ 
 	    "$(MULTILIB_EXCLUSIONS)" \
 	    "$(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: genmultilib
===================================================================
--- genmultilib	(revision 188931)
+++ 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
Index: gcc.c
===================================================================
--- gcc.c	(revision 188931)
+++ 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
@@ -2081,6 +2086,7 @@ 
   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;
@@ -2098,11 +2104,14 @@ 
     }
   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;
@@ -2111,16 +2120,15 @@ 
 	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);
 	}
 
@@ -2149,6 +2157,16 @@ 
 		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))
@@ -2974,6 +2992,9 @@ 
   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\
@@ -3257,6 +3278,7 @@ 
     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:
@@ -4910,6 +4932,15 @@ 
 		  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);
@@ -6575,6 +6606,15 @@ 
       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)
@@ -7558,10 +7598,26 @@ 
 	    q++;
 	  if (q < end)
 	    {
-	      char *new_multilib_os_dir = XNEWVEC (char, end - q);
+	      const char *q2 = q + 1;
+	      char *new_multilib_os_dir;
+
+	      while (q2 < end && *q2 != ':')
+		q2++;
+	      if (*q2 == ':')
+		end = q2;
+	      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;
+	      multilib_os_dir = *new_multilib_os_dir ? new_multilib_os_dir : ".";
+
+	      end = this_path + this_path_len;
+	      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;
 	    }
 	}
@@ -7623,7 +7679,7 @@ 
       /* 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] == ':')
+      if (this_path[0] == '.' && this_path[1] == ':' && this_path[2] != ':')
 	skip = 1;
 
       /* Check for matches with the multilib_exclusions. We don't bother
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-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: config/i386/t-linux64
===================================================================
--- config/i386/t-linux64	(revision 188931)
+++ 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 $(SYSTEM_HEADER_DIR))/../../usr/lib32),../lib32,../lib)
+MULTILIB_OSDIRNAMES = m64=../lib64$(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
Index: common.opt
===================================================================
--- common.opt	(revision 188931)
+++ common.opt	(working copy)
@@ -345,6 +345,9 @@ 
 -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=)
 
@@ -2298,6 +2301,10 @@ 
 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
 
@@ -2354,6 +2361,9 @@ 
 
 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: doc/install.texi
===================================================================
--- doc/install.texi	(revision 188931)
+++ doc/install.texi	(working copy)
@@ -1038,6 +1038,11 @@ 
 conventions, etc.@: should not be built.  The default is to build a
 predefined set of them.
 
+@item --enable-multiarch
+Specify wether to enable or disable multiarch support.  The default is
+to detect for glibc start files in a multiarch location, and enable it
+if the files are found.
+
 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 188931)
+++ 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: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 188931)
+++ doc/invoke.texi	(working copy)
@@ -6111,6 +6111,11 @@ 
 @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: config.gcc
===================================================================
--- config.gcc	(revision 188931)
+++ config.gcc	(working copy)
@@ -3445,10 +3445,15 @@ 
 
 	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: incpath.c
===================================================================
--- incpath.c	(revision 188931)
+++ 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);
 	}