diff --git a/pkgs/build-support/gcc-wrapper/builder.sh b/pkgs/build-support/gcc-wrapper/builder.sh
index d3b1f433559..92d187ab84d 100755
--- a/pkgs/build-support/gcc-wrapper/builder.sh
+++ b/pkgs/build-support/gcc-wrapper/builder.sh
@@ -57,6 +57,7 @@ test -z "$isNative" && echo $glibc > $out/nix-support/orig-glibc
 
 sed \
     -e "s^@isNative@^$isNative^g" \
+    -e "s^@enforcePurity@^$enforcePurity^g" \
     -e "s^@gcc@^$gcc^g" \
     -e "s^@glibc@^$glibc^g" \
     < $setupHook > $out/nix-support/setup-hook
diff --git a/pkgs/build-support/gcc-wrapper/default.nix b/pkgs/build-support/gcc-wrapper/default.nix
index da189661164..11282e131da 100644
--- a/pkgs/build-support/gcc-wrapper/default.nix
+++ b/pkgs/build-support/gcc-wrapper/default.nix
@@ -17,6 +17,7 @@ derivation {
   gccWrapper = ./gcc-wrapper.sh;
   ldWrapper = ./ld-wrapper.sh;
   inherit name stdenv isNative gcc glibc binutils;
+  enforcePurity = if isNative then false else gcc.noSysDirs;
   langC = if isNative then true else gcc.langC;
   langCC = if isNative then true else gcc.langCC;
   langF77 = if isNative then false else gcc.langF77;
diff --git a/pkgs/build-support/gcc-wrapper/gcc-wrapper.sh b/pkgs/build-support/gcc-wrapper/gcc-wrapper.sh
index 59f38086f32..6cb3493f6bf 100644
--- a/pkgs/build-support/gcc-wrapper/gcc-wrapper.sh
+++ b/pkgs/build-support/gcc-wrapper/gcc-wrapper.sh
@@ -10,6 +10,7 @@ if test -z "$NIX_GLIBC_FLAGS_SET"; then
     NIX_LDFLAGS="@ldflags@ $NIX_LDFLAGS"
 fi
 
+
 # Figure out if linker flags should be passed.  GCC prints annoying
 # warnings when they are not needed.
 dontLink=0
@@ -33,6 +34,40 @@ else
     done
 fi
 
+
+# Optionally filter out paths not refering to the store.
+skip () {
+    if test "$NIX_DEBUG" = "1"; then
+        echo "skipping impure path $1" >&2
+    fi
+}
+
+params=("$@")
+if test "$NIX_ENFORCE_PURITY" = "1" -a -n "$NIX_STORE"; then
+    rest=()
+    n=0
+    while test $n -lt ${#params[*]}; do
+        p=${params[n]}
+        p2=${params[$((n+1))]}
+        if test "${p:0:3}" = "-L/" -a "${p:2:${#NIX_STORE}}" != "$NIX_STORE"; then
+            skip $p
+        elif test "$p" = "-L" -a "${p2:0:${#NIX_STORE}}" != "$NIX_STORE"; then
+            n=$((n + 1)); skip $p2
+        elif test "${p:0:3}" = "-I/" -a "${p:2:${#NIX_STORE}}" != "$NIX_STORE"; then
+            skip $p
+        elif test "$p" = "-I" -a "${p2:0:${#NIX_STORE}}" != "$NIX_STORE"; then
+            n=$((n + 1)); skip $p2
+        elif test "$p" = "-isystem" -a "${p2:0:${#NIX_STORE}}" != "$NIX_STORE"; then
+            n=$((n + 1)); skip $p2
+        else
+            rest=("${rest[@]}" "$p")
+        fi
+        n=$((n + 1))
+    done
+    params=("${rest[@]}")
+fi
+
+
 # Add the flags for the C compiler proper.
 extra=($NIX_CFLAGS_COMPILE)
 
@@ -58,7 +93,7 @@ fi
 # Optionally print debug info.
 if test "$NIX_DEBUG" = "1"; then
   echo "original flags to @gcc@:" >&2
-  for i in "$@"; do
+  for i in "${params[@]}"; do
       echo "  $i" >&2
   done
   echo "extra flags to @gcc@:" >&2
@@ -71,4 +106,4 @@ if test -n "$NIX_GCC_WRAPPER_EXEC_HOOK"; then
     . "$NIX_GCC_WRAPPER_EXEC_HOOK"
 fi
 
-exec @gcc@ "$@" ${extra[@]}
+exec @gcc@ "${params[@]}" ${extra[@]}
diff --git a/pkgs/build-support/gcc-wrapper/setup-hook.sh b/pkgs/build-support/gcc-wrapper/setup-hook.sh
index a4c52ba803d..07c3b54b473 100644
--- a/pkgs/build-support/gcc-wrapper/setup-hook.sh
+++ b/pkgs/build-support/gcc-wrapper/setup-hook.sh
@@ -13,3 +13,5 @@ envHooks=(${envHooks[@]} addCVars)
 if test -z "@isNative@"; then
     PATH=$PATH:@gcc@/bin:@glibc@/bin
 fi
+
+export NIX_ENFORCE_PURITY=@enforcePurity@
diff --git a/pkgs/development/compilers/gcc-new/default.nix b/pkgs/development/compilers/gcc-new/default.nix
index 0d44cbe74b0..e2311a26023 100644
--- a/pkgs/development/compilers/gcc-new/default.nix
+++ b/pkgs/development/compilers/gcc-new/default.nix
@@ -1,19 +1,16 @@
-{ stdenv, fetchurl
+{ stdenv, fetchurl, noSysDirs ? true
 , langC ? true, langCC ? true, langF77 ? false
 }:
 
 assert langC;
 
 derivation {
-  name = "gcc-3.3.2";
+  name = "gcc-3.3.3";
   system = stdenv.system;
   builder = ./builder.sh;
   src = fetchurl {
-#    url = ftp://ftp.nluug.nl/mirror/languages/gcc/releases/gcc-3.3.3/gcc-3.3.3.tar.bz2;
-#    md5 = "3c6cfd9fcd180481063b4058cf6faff2";
-    url = ftp://ftp.nluug.nl/pub/gnu/gcc/gcc-3.3.2/gcc-3.3.2.tar.bz2;
-    md5 = "65999f654102f5438ac8562d13a6eced";
+    url = ftp://ftp.nluug.nl/mirror/languages/gcc/releases/gcc-3.3.3/gcc-3.3.3.tar.bz2;
+    md5 = "3c6cfd9fcd180481063b4058cf6faff2";
   };
-  noSysDirs = stdenv.noSysDirs;
-  inherit stdenv langC langCC langF77;
+  inherit stdenv noSysDirs langC langCC langF77;
 }
diff --git a/pkgs/development/libraries/glibc/builder.sh b/pkgs/development/libraries/glibc/builder.sh
index 7503e73a171..249ab0872ac 100755
--- a/pkgs/development/libraries/glibc/builder.sh
+++ b/pkgs/development/libraries/glibc/builder.sh
@@ -15,7 +15,7 @@ LDFLAGS=-Wl,-S ../glibc-*/configure --prefix=$out --enable-add-ons --disable-pro
 
 make || exit 1
 make install || exit 1
-make localedata/install-locales || exit 1
+#make localedata/install-locales || exit 1
 strip -S $out/lib/*.a $out/lib/*.so $out/lib/gconv/*.so
 strip -s $out/bin/* $out/sbin/* $out/libexec/*
 
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index c163c04cb51..4530a1b1319 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -21,6 +21,11 @@ param5=@param5@
 . @preHook@
 
 
+if test -f @gcc@/nix-support/setup-hook; then
+    . @gcc@/nix-support/setup-hook
+fi
+
+    
 # Recursively find all build inputs.
 findInputs()
 {
@@ -76,6 +81,10 @@ export NIX_STRIP_DEBUG=1
 export NIX_CFLAGS_STRIP="-g0 -Wl,-s"
 
 
+# Where is the store?  This is required for purity checking.
+export NIX_STORE=$(dirname $out)/ # !!! hack
+
+
 # Execute the post-hook.
 . @postHook@
 
diff --git a/pkgs/system/all-packages.nix b/pkgs/system/all-packages.nix
index f1a0c917f71..666d0e67273 100644
--- a/pkgs/system/all-packages.nix
+++ b/pkgs/system/all-packages.nix
@@ -12,6 +12,6 @@
   # Select the right instantiation.
   body =
     if system == "i686-linux"
-    then stdenvs.stdenvLinuxPkgs
+    then stdenvs.stdenvNativePkgs #stdenvs.stdenvLinuxPkgs
     else stdenvs.stdenvNixPkgs;
 }
diff --git a/pkgs/system/stdenvs.nix b/pkgs/system/stdenvs.nix
index 34804ad55d8..06a9fc50fed 100644
--- a/pkgs/system/stdenvs.nix
+++ b/pkgs/system/stdenvs.nix
@@ -8,12 +8,19 @@
 {system, allPackages}: rec {
 
 
+  # Trivial environment used for building other environments.
+  stdenvInitial = (import ../stdenv/initial) {
+    name = "stdenv-initial";
+    inherit system;
+  };
+
+
   # The native (i.e., impure) build environment.  This one uses the
   # tools installed on the system outside of the Nix environment,
   # i.e., the stuff in /bin, /usr/bin, etc.  This environment should
   # be used with care, since many Nix packages will not build properly
   # with it (e.g., because they require GNU Make).
-  stdenvNative = (import ../stdenv/native) {system = system;};
+  stdenvNative = (import ../stdenv/native) {stdenv = stdenvInitial;};
 
   stdenvNativePkgs = allPackages {system = system; stdenv = stdenvNative;};
 
diff --git a/pkgs/test/simple/builder.sh b/pkgs/test/simple/builder.sh
index c155bdc3615..282fc520bd1 100755
--- a/pkgs/test/simple/builder.sh
+++ b/pkgs/test/simple/builder.sh
@@ -4,7 +4,7 @@ export NIX_DEBUG=1
 
 . $stdenv/setup
 
-export NIX_CFLAGS_COMPILE="-v $NIX_CFLAGS_COMPILE"
+#export NIX_CFLAGS_COMPILE="-v $NIX_CFLAGS_COMPILE"
 
 mkdir $out
 mkdir $out/bin
@@ -19,7 +19,8 @@ int main(int argc, char * * argv)
 }
 EOF
 
-gcc hello.c -o $out/bin/hello
+#gcc -I/nix/store/foo -I /nix/store/foo -I/usr/lib -I /usr/lib hello.c -o $out/bin/hello
+gcc -L /nix/store/abcd/lib -isystem /usr/lib hello.c -o $out/bin/hello
 
 $out/bin/hello