TARGET=$1
ARCH=$2
SMP=$3
CC=$4

# If compile.h exists already and we don't own autoconf.h
# (i.e. we're not the same user who did make *config), don't
# modify compile.h
# So "sudo make install" won't change the "compiled by <user>"
# do "compiled by root"

if [ -r $TARGET -a ! -O include/linux/autoconf.h ]; then
  echo ' (not modified)'
  exit 0
fi

# Do not expand names
set -f

if [ -r .version ]; then
  VERSION=`cat .version`
else
  VERSION=0
  echo 0 > .version
fi


UTS_VERSION="#$VERSION"
if [ -n "$SMP" ] ; then UTS_VERSION="$UTS_VERSION SMP"; fi
UTS_VERSION="$UTS_VERSION `LANG=C date`"

# Truncate to maximum length

UTS_LEN=64
UTS_TRUNCATE="sed -e s/\(.\{1,$UTS_LEN\}\).*/\1/"

# Generate a temporary compile.h

( echo /\* This file is auto generated, version $VERSION \*/

  echo \#define UTS_MACHINE \"$ARCH\"

  echo \#define UTS_VERSION \"`echo $UTS_VERSION | $UTS_TRUNCATE`\"

  echo \#define LINUX_COMPILE_TIME \"`LANG=C date +%T`\"
  echo \#define LINUX_COMPILE_BY \"`whoami`\"
  echo \#define LINUX_COMPILE_HOST \"`hostname | $UTS_TRUNCATE`\"

  if [ -x /bin/dnsdomainname ]; then
    echo \#define LINUX_COMPILE_DOMAIN \"`dnsdomainname | $UTS_TRUNCATE`\"
  elif [ -x /bin/domainname ]; then
    echo \#define LINUX_COMPILE_DOMAIN \"`domainname | $UTS_TRUNCATE`\"
  else
    echo \#define LINUX_COMPILE_DOMAIN
  fi

  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | tail -1`\"
) > .tmpcompile

# Only replace the real compile.h if the new one is different,
# in order to preserve the timestamp and avoid unnecessary
# recompilations.
# We don't consider the file changed if only the date/time changed.
# A kernel config change will increase the generation number, thus
# causing compile.h to be updated (including date/time) due to the 
# changed comment in the
# first line.

if [ -r $TARGET ] && \
      grep -v 'UTS_VERSION\|LINUX_COMPILE_TIME' $TARGET > .tmpver.1 && \
      grep -v 'UTS_VERSION\|LINUX_COMPILE_TIME' .tmpcompile > .tmpver.2 && \
      cmp -s .tmpver.1 .tmpver.2; then
   echo ' (unchanged)'
   rm -f .tmpcompile
else
   echo ' (updated)'
   mv -f .tmpcompile $TARGET
fi
#rm -f .tmpver.1 .tmpver.2