Improve the config/parse_types.sh helper script

Fix a potential security problem if e2fsprogs is built as root (as
Gentoo does!).  In addition fix the script and how it is called from
the configure script so that it does the right thing when
cross-compiling.

Fixes-Gentoo-bug: #146903

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

config/parse-types.sh

@@ -1,15 +1,6 @@
 #!/bin/sh
 
-ASM_TYPES=/usr/include/asm/types.h
-
-if test ! -f $ASM_TYPES
-then
-    echo "" > asm_types.h
-    echo "No asm_types file found"
-    exit 1
-fi
-
-cat > /tmp/sed.script << "EOF"
+cat > sed.script << "EOF"
 /^#/d
 /^$/d
 s/__extension__ //
@@ -17,11 +8,16 @@ s/typedef \(.*\) __u\([1-9]*\);/#define __U\2_TYPEDEF \1/
 s/typedef \(.*\) __s\([1-9]*\);/#define __S\2_TYPEDEF \1/
 EOF
 
-gcc -E $ASM_TYPES | sed -f /tmp/sed.script | grep ^# > asm_types.h
+echo '#include <asm/types.h>' | ${CPP-${CC-gcc} -E} - | \
+    sed -f sed.script | grep ^# > asm_types.h
+
+rm sed.script
 
 cp asm_types.h asm_types.c
 
 cat >> asm_types.c <<EOF
+#include <stdio.h>
+#include <stdlib.h>
 main(int argc, char **argv)
 {
 #ifdef __U8_TYPEDEF
@@ -102,7 +98,7 @@ main(int argc, char **argv)
 }
 EOF
 
-cc -o asm_types asm_types.c
+${BUILD_CC-${CC-gcc}} -o asm_types asm_types.c
 if ! ./asm_types 
 then
     echo "Problem detected with asm_types.h"

configure.in

@@ -82,6 +82,7 @@ if test -z "$CC" ; then CC=cc; fi
 export CC
 AC_SUBST([CC])
 AC_PROG_CC
+AC_PROG_CPP
 dnl
 dnl set $(LD) from --with-linker=value
 dnl
@@ -636,7 +637,7 @@ AC_SUBST(SIZEOF_INT)
 AC_SUBST(SIZEOF_LONG)
 AC_SUBST(SIZEOF_LONG_LONG)
 AC_C_BIGENDIAN
-/bin/sh $ac_aux_dir/parse-types.sh
+BUILD_CC="$BUILD_CC" CPP="$CPP" /bin/sh $ac_aux_dir/parse-types.sh
 ASM_TYPES_HEADER=./asm_types.h
 AC_SUBST_FILE(ASM_TYPES_HEADER)
 dnl