PATCH: Take advantage of ld --sysroot

[Mark Mitchell <mark at codesourcery dot com>]

Richard Sandiford added --sysroot support to GNU ld a while back.
This patch (originally developed for csl-arm-branch) makes GCC
automatically pass --sysroot to the linker when that makes sense.
Tested on x86_64-unknonwn-linux-gnu, with a linker that had sysroot
support and one without.  Applied on the mainline.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com

2005-04-27  Mark Mitchell  <mark@codesourcery.com>

	* configure.ac: Check for ld --sysroot support.
	* gcc.c: Document %R specifier for specs.
	(SYSROOT_SPEC): New macro.
	(sysroot_spec): New variable.
	(static_specs): Add sysroot_spec.
	(main): Pass the sysroot spec to the linker if appropriate.
	* configure: Regenerated.
	* config.in: Likewise.

Index: configure.ac
===================================================================
RCS file: /cvs/gcc/gcc/gcc/configure.ac,v
retrieving revision 2.105
diff -c -5 -p -r2.105 configure.ac
*** configure.ac	13 Apr 2005 09:13:27 -0000	2.105
--- configure.ac	27 Apr 2005 20:15:49 -0000
*************** EOF
*** 3022,3031 ****
--- 3022,3048 ----
      [Define if your PowerPC64 linker only needs function descriptor syms.])
      fi
      ;;
  esac
  
+ AC_CACHE_CHECK(linker --sysroot support,
+   gcc_cv_ld_sysroot,
+   [gcc_cv_ld_sysroot=no
+   if test $in_tree_ld = yes ; then
+       if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 16 -o "$gcc_cv_gld_major_version" -gt 2 ; then
+         gcc_cv_ld_sysroot = yes
+       fi
+   elif test x$gcc_cv_ld != x; then 
+     if $gcc_cv_ld --help 2>/dev/null | grep sysroot > /dev/null; then
+       gcc_cv_ld_sysroot=yes
+     fi
+   fi])
+ if test x"$gcc_cv_ld_sysroot" = xyes; then
+   AC_DEFINE(HAVE_LD_SYSROOT, 1,
+   [Define if your linker supports --sysroot.])
+ fi	  
+ 
  if test x$with_sysroot = x && test x$host = x$target \
     && test "$prefix" != "/usr" && test "x$prefix" != "x$local_prefix" ; then
    AC_DEFINE_UNQUOTED(PREFIX_INCLUDE_DIR, "$prefix/include",
  [Define to PREFIX/include if cpp should also search that directory.])
  fi
Index: gcc.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/gcc.c,v
retrieving revision 1.455
diff -c -5 -p -r1.455 gcc.c
*** gcc.c	26 Apr 2005 00:23:52 -0000	1.455
--- gcc.c	27 Apr 2005 20:15:49 -0000
*************** or with constant text in a single argume
*** 458,467 ****
--- 458,469 ----
   %D	Dump out a -L option for each directory in startfile_prefixes.
  	If multilib_dir is set, extra entries are generated with it affixed.
   %l     process LINK_SPEC as a spec.
   %L     process LIB_SPEC as a spec.
   %G     process LIBGCC_SPEC as a spec.
+  %R     Output the concatenation of target_system_root and
+         target_sysroot_suffix.
   %S     process STARTFILE_SPEC as a spec.  A capital S is actually used here.
   %E     process ENDFILE_SPEC as a spec.  A capital E is actually used here.
   %C     process CPP_SPEC as a spec.
   %1	process CC1_SPEC as a spec.
   %2	process CC1PLUS_SPEC as a spec.
*************** proper position among the other output f
*** 699,708 ****
--- 701,714 ----
  
  #ifndef STARTFILE_PREFIX_SPEC
  # define STARTFILE_PREFIX_SPEC ""
  #endif
  
+ #ifndef SYSROOT_SPEC
+ # define SYSROOT_SPEC "--sysroot=%R"
+ #endif
+ 
  #ifndef SYSROOT_SUFFIX_SPEC
  # define SYSROOT_SUFFIX_SPEC ""
  #endif
  
  #ifndef SYSROOT_HEADERS_SUFFIX_SPEC
*************** static const char *startfile_spec = STAR
*** 726,735 ****
--- 732,742 ----
  static const char *switches_need_spaces = SWITCHES_NEED_SPACES;
  static const char *linker_name_spec = LINKER_NAME;
  static const char *link_command_spec = LINK_COMMAND_SPEC;
  static const char *link_libgcc_spec = LINK_LIBGCC_SPEC;
  static const char *startfile_prefix_spec = STARTFILE_PREFIX_SPEC;
+ static const char *sysroot_spec = SYSROOT_SPEC;
  static const char *sysroot_suffix_spec = SYSROOT_SUFFIX_SPEC;
  static const char *sysroot_hdrs_suffix_spec = SYSROOT_HEADERS_SUFFIX_SPEC;
  
  /* Standard options to cpp, cc1, and as, to reduce duplication in specs.
     There should be no need to override these in target dependent files,
*************** static struct spec_list static_specs[] =
*** 1530,1539 ****
--- 1537,1547 ----
    INIT_STATIC_SPEC ("link_libgcc",		&link_libgcc_spec),
    INIT_STATIC_SPEC ("md_exec_prefix",		&md_exec_prefix),
    INIT_STATIC_SPEC ("md_startfile_prefix",	&md_startfile_prefix),
    INIT_STATIC_SPEC ("md_startfile_prefix_1",	&md_startfile_prefix_1),
    INIT_STATIC_SPEC ("startfile_prefix_spec",	&startfile_prefix_spec),
+   INIT_STATIC_SPEC ("sysroot_spec",             &sysroot_spec),
    INIT_STATIC_SPEC ("sysroot_suffix_spec",	&sysroot_suffix_spec),
    INIT_STATIC_SPEC ("sysroot_hdrs_suffix_spec",	&sysroot_hdrs_suffix_spec),
  };
  
  #ifdef EXTRA_SPECS		/* additional specs needed */
*************** main (int argc, const char **argv)
*** 6146,6155 ****
--- 6154,6176 ----
          error ("spec failure: more than one arg to SYSROOT_SUFFIX_SPEC.");
        else if (argbuf_index == 1)
          target_sysroot_suffix = xstrdup (argbuf[argbuf_index -1]);
      }
  
+ #ifdef HAVE_LD_SYSROOT
+   /* Pass the --sysroot option to the linker, if it supports that.  If
+      there is a sysroot_suffix_spec, it has already been processed by
+      this point, so target_system_root really is the system root we
+      should be using.  */
+   if (target_system_root)
+     {
+       obstack_grow (&obstack, "%(sysroot_spec) ", strlen ("%(sysroot_spec) "));
+       obstack_grow0 (&obstack, link_spec, strlen (link_spec));
+       set_spec ("link", obstack_finish (&obstack));
+     }
+ #endif
+ 
    /* Process sysroot_hdrs_suffix_spec.  */
    if (*sysroot_hdrs_suffix_spec != 0
        && do_spec_2 (sysroot_hdrs_suffix_spec) == 0)
      {
        if (argbuf_index > 1)