diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index c91f26294a4..bec4dc97726 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2006-05-01  DJ Delorie  <dj@redhat.com>
+
+	* vec.c: Include bconfig.h when appropriate.
+	* Makefile.in (build/vec.o): Adjust dependencies.
+	* mkconfig.sh: Make sure config.h isn't used for build machine
+	compiles.
+
 2006-05-01  Zdenek Dvorak <dvorakz@suse.cz>
 
 	* tree-into-ssa.c (phis_to_rewrite, blocks_with_phis_to_rewrite): New
diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 1833128ebe4..4239808a06c 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2927,7 +2927,7 @@ build/read-rtl.o: read-rtl.c $(BCONFIG_H) $(SYSTEM_H) coretypes.h	\
   $(GTM_H) $(RTL_BASE_H) $(OBSTACK_H) $(HASHTAB_H) gensupport.h
 build/rtl.o: rtl.c $(BCONFIG_H) coretypes.h $(GTM_H) $(SYSTEM_H)	\
   $(RTL_H) $(REAL_H) $(GGC_H) errors.h
-build/vec.o : vec.c $(CONFIG_H) $(SYSTEM_H) $(TREE_H) coretypes.h vec.h \
+build/vec.o : vec.c $(BCONFIG_H) $(SYSTEM_H) $(TREE_H) coretypes.h vec.h \
    $(GGC_H) toplev.h
 build/gencondmd.o : build/gencondmd.c $(BCONFIG_H) $(SYSTEM_H)		\
   coretypes.h $(GTM_H) insn-constants.h $(RTL_H) $(TM_P_H)		\
diff --git a/gcc/mkconfig.sh b/gcc/mkconfig.sh
index 78c9a993666..9ffd200b9cf 100644
--- a/gcc/mkconfig.sh
+++ b/gcc/mkconfig.sh
@@ -1,6 +1,6 @@
 #! /bin/sh
 
-# Copyright (C) 2001, 2002 Free Software Foundation, Inc.
+# Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.
 # This file is part of GCC.
 
 # GCC is free software; you can redistribute it and/or modify
@@ -41,6 +41,14 @@ header_guard=GCC_`echo ${output} | sed -e ${hg_sed_expr}`
 echo "#ifndef ${header_guard}" >> ${output}T
 echo "#define ${header_guard}" >> ${output}T
 
+# A special test to ensure that build-time files don't blindly use
+# config.h.
+if test x"$output" == x"config.h"; then
+  echo "#ifdef GENERATOR_FILE" >> ${output}T
+  echo "#error config.h is for the host, not build, machine." >> ${output}T
+  echo "#endif" >> ${output}T
+fi
+
 # Define TARGET_CPU_DEFAULT if the system wants one.
 # This substitutes for lots of *.h files.
 if [ "$TARGET_CPU_DEFAULT" != "" ]; then
diff --git a/gcc/vec.c b/gcc/vec.c
index b6a1d784088..5d5687475ec 100644
--- a/gcc/vec.c
+++ b/gcc/vec.c
@@ -1,5 +1,5 @@
 /* Vector API for GNU compiler.
-   Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
    Contributed by Nathan Sidwell <nathan@codesourcery.com>
 
 This file is part of GCC.
@@ -19,7 +19,14 @@ along with GCC; see the file COPYING.  If not, write to the Free
 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
 02110-1301, USA.  */
 
+/* This file is compiled twice: once for the generator programs
+   once for the compiler.  */
+#ifdef GENERATOR_FILE
+#include "bconfig.h"
+#else
 #include "config.h"
+#endif
+
 #include "system.h"
 #include "ggc.h"
 #include "vec.h"