       gcc/
       2008-07-02  Joseph Myers  <joseph@codesourcery.com>
       * c-incpath.c: Include toplev.h.
       (merge_include_chains): Use warning instead of cpp_error for
       system directory poisoning diagnostic.
       * Makefile.in (c-incpath.o): Depend on toplev.h.
       * gcc.c (LINK_COMMAND_SPEC): Pass
       --error-poison-system-directories if
       -Werror=poison-system-directories.

       2007-06-13  Joseph Myers  <joseph@codesourcery.com>
       * common.opt (--Wno-poison-system-directories): New.
       * doc/invoke.texi (-Wno-poison-system-directories): Document.
       * c-incpath.c: Include flags.h.
       (merge_include_chains): Check flag_poison_system_directories.
       * gcc.c (LINK_COMMAND_SPEC): Pass --no-poison-system-directories
       to linker if -Wno-poison-system-directories.
       * Makefile.in (c-incpath.o): Depend on $(FLAGS_H).

       2007-03-20  Daniel Jacobowitz  <dan@codesourcery.com>
                   Joseph Myers  <joseph@codesourcery.com>
       * configure.ac (--enable-poison-system-directories): New option.
       * configure, config.in: Regenerate.
       * c-incpath.c (merge_include_chains): If
       ENABLE_POISON_SYSTEM_DIRECTORIES defined, warn for use of
       /usr/include, /usr/local/include or /usr/X11R6/include.

Index: gcc-4.5.0/gcc/common.opt
===================================================================
--- gcc-4.5.0.orig/gcc/common.opt	2010-03-17 20:01:09.000000000 -0700
+++ gcc-4.5.0/gcc/common.opt	2010-06-25 11:35:39.965383734 -0700
@@ -152,6 +152,10 @@
 Common Var(warn_padded) Warning
 Warn when padding is required to align structure members
 
+Wpoison-system-directories
+Common Var(flag_poison_system_directories) Init(1) Warning
+Warn for -I and -L options using system directories if cross compiling
+
 Wshadow
 Common Var(warn_shadow) Warning
 Warn when one local variable shadows another
Index: gcc-4.5.0/gcc/config.in
===================================================================
--- gcc-4.5.0.orig/gcc/config.in	2010-04-14 02:30:07.000000000 -0700
+++ gcc-4.5.0/gcc/config.in	2010-06-25 11:35:39.969383588 -0700
@@ -132,6 +132,12 @@
 #endif
 
 
+/* Define to warn for use of native system header directories */
+#ifndef USED_FOR_TARGET
+#undef ENABLE_POISON_SYSTEM_DIRECTORIES
+#endif
+
+
 /* Define if you want all operations on RTL (the basic data structure of the
    optimizer and back end) to be checked for dynamic type safety at runtime.
    This is quite expensive. */
Index: gcc-4.5.0/gcc/configure.ac
===================================================================
--- gcc-4.5.0.orig/gcc/configure.ac	2010-06-25 11:34:01.433382161 -0700
+++ gcc-4.5.0/gcc/configure.ac	2010-06-25 11:35:39.969383588 -0700
@@ -4276,6 +4276,16 @@
 fi)
 AC_SUBST(slibdir)
 
+AC_ARG_ENABLE([poison-system-directories],
+             AS_HELP_STRING([--enable-poison-system-directories],
+                            [warn for use of native system header directories]),,
+             [enable_poison_system_directories=no])
+if test "x${enable_poison_system_directories}" = "xyes"; then
+  AC_DEFINE([ENABLE_POISON_SYSTEM_DIRECTORIES],
+           [1],
+           [Define to warn for use of native system header directories])
+fi
+
 # Substitute configuration variables
 AC_SUBST(subdirs)
 AC_SUBST(srcdir)
Index: gcc-4.5.0/gcc/doc/invoke.texi
===================================================================
--- gcc-4.5.0.orig/gcc/doc/invoke.texi	2010-04-06 07:02:22.000000000 -0700
+++ gcc-4.5.0/gcc/doc/invoke.texi	2010-06-25 11:35:39.992666345 -0700
@@ -252,6 +252,7 @@
 -Woverlength-strings  -Wpacked  -Wpacked-bitfield-compat  -Wpadded @gol
 -Wparentheses  -Wpedantic-ms-format -Wno-pedantic-ms-format @gol
 -Wpointer-arith  -Wno-pointer-to-int-cast @gol
+-Wno-poison-system-directories @gol
 -Wredundant-decls @gol
 -Wreturn-type  -Wsequence-point  -Wshadow @gol
 -Wsign-compare  -Wsign-conversion  -Wstack-protector @gol
@@ -3603,6 +3604,14 @@
 option will @emph{not} warn about unknown pragmas in system
 headers---for that, @option{-Wunknown-pragmas} must also be used.
 
+@item -Wno-poison-system-directories
+@opindex Wno-poison-system-directories
+Do not warn for @option{-I} or @option{-L} options using system
+directories such as @file{/usr/include} when cross compiling.  This
+option is intended for use in chroot environments when such
+directories contain the correct headers and libraries for the target
+system rather than the host.
+
 @item -Wfloat-equal
 @opindex Wfloat-equal
 @opindex Wno-float-equal
Index: gcc-4.5.0/gcc/gcc.c
===================================================================
--- gcc-4.5.0.orig/gcc/gcc.c	2010-02-11 04:23:08.000000000 -0800
+++ gcc-4.5.0/gcc/gcc.c	2010-06-25 11:35:40.009381858 -0700
@@ -792,6 +792,8 @@
     %{flto} %{fwhopr} %l " LINK_PIE_SPEC \
    "%X %{o*} %{A} %{d} %{e*} %{m} %{N} %{n} %{r}\
     %{s} %{t} %{u*} %{x} %{z} %{Z} %{!A:%{!nostdlib:%{!nostartfiles:%S}}}\
+    %{Wno-poison-system-directories:--no-poison-system-directories}\
+    %{Werror=poison-system-directories:--error-poison-system-directories}\
     %{static:} %{L*} %(mfwrap) %(link_libgcc) %o\
     %{fopenmp|ftree-parallelize-loops=*:%:include(libgomp.spec)%(link_gomp)} %(mflib)\
     %{fprofile-arcs|fprofile-generate*|coverage:-lgcov}\
Index: gcc-4.5.0/gcc/incpath.c
===================================================================
--- gcc-4.5.0.orig/gcc/incpath.c	2009-11-25 02:55:54.000000000 -0800
+++ gcc-4.5.0/gcc/incpath.c	2010-06-25 11:35:40.017209818 -0700
@@ -353,6 +353,24 @@
 	}
       fprintf (stderr, _("End of search list.\n"));
     }
+
+#ifdef ENABLE_POISON_SYSTEM_DIRECTORIES
+  if (flag_poison_system_directories)
+    {
+       struct cpp_dir *p;
+
+       for (p = heads[QUOTE]; p; p = p->next)
+         {
+          if ((!strncmp (p->name, "/usr/include", 12))
+              || (!strncmp (p->name, "/usr/local/include", 18))
+              || (!strncmp (p->name, "/usr/X11R6/include", 18)))
+            warning (OPT_Wpoison_system_directories,
+                     "include location \"%s\" is unsafe for "
+                     "cross-compilation",
+                     p->name);
+         }
+    }
+#endif
 }
 
 /* Use given -I paths for #include "..." but not #include <...>, and
diff -ur gcc-4.5.0.orig/gcc/Makefile.in gcc-4.5.0/gcc/Makefile.in
--- gcc-4.5.0.orig/gcc/Makefile.in	2010-09-29 17:13:49.164088845 -0500
+++ gcc-4.5.0/gcc/Makefile.in	2010-09-29 18:48:19.300178501 -0500
@@ -1965,7 +1965,7 @@
 
 incpath.o: incpath.c incpath.h $(CONFIG_H) $(SYSTEM_H) $(CPPLIB_H) \
 		intl.h prefix.h coretypes.h $(TM_H) cppdefault.h $(TARGET_H) \
-		$(MACHMODE_H)
+		$(MACHMODE_H) $(FLAGS_H) toplev.h
 
 c-decl.o : c-decl.c $(CONFIG_H) $(SYSTEM_H) coretypes.h $(TM_H) $(TREE_H) \
     $(RTL_H) $(C_TREE_H) $(GGC_H) $(TARGET_H) $(FLAGS_H) $(FUNCTION_H) output.h \
diff -ur gcc-4.5.0.orig/gcc/configure gcc-4.5.0/gcc/configure
--- gcc-4.5.0.orig/gcc/configure	2010-09-29 14:58:31.702054881 -0500
+++ gcc-4.5.0/gcc/configure	2010-09-29 18:46:31.486068500 -0500
@@ -913,6 +913,7 @@
 enable_maintainer_mode
 enable_version_specific_runtime_libs
 with_slibdir
+enable_poison_system_directories
 enable_plugin
 enable_target_optspace
 '
@@ -1621,6 +1622,8 @@
   --enable-version-specific-runtime-libs
                           specify that runtime libraries should be
                           installed in a compiler-specific directory
+  --enable-poison-system-directories
+                          warn for use of native system header directories
   --enable-plugin         enable plugin support
 
 Optional Packages:
@@ -25339,6 +25377,19 @@
 
 
 
+# Check whether --enable-poison-system-directories was given.
+if test "${enable_poison_system_directories+set}" = set; then :
+  enableval=$enable_poison_system_directories;
+else
+  enable_poison_system_directories=no
+fi
+
+if test "x${enable_poison_system_directories}" = "xyes"; then
+
+$as_echo "#define ENABLE_POISON_SYSTEM_DIRECTORIES 1" >>confdefs.h
+
+fi
+
 # Substitute configuration variables
 
 
