#

# Copyright (c) 2011, 2017, Oracle and/or its affiliates. All rights reserved.

# DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

#

# This code is free software; you can redistribute it and/or modify it

# under the terms of the GNU General Public License version 2 only, as

# published by the Free Software Foundation.  Oracle designates this

# particular file as subject to the "Classpath" exception as provided

# by Oracle in the LICENSE file that accompanied this code.

#

# This code is distributed in the hope that it will be useful, but WITHOUT

# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

# version 2 for more details (a copy is included in the LICENSE file that

# accompanied this code).

#

# You should have received a copy of the GNU General Public License version

# 2 along with this work; if not, write to the Free Software Foundation,

# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

#

# Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

# or visit www.oracle.com if you need additional information or have any

# questions.

#

########################################################################

# This file handles detection of the Boot JDK. The Boot JDK detection

# process has been developed as a response to solve a complex real-world

# problem. Initially, it was simple, but it has grown as platform after

# platform, idiosyncracy after idiosyncracy has been supported.

#

# The basic idea is this:

# 1) You need an acceptable *) JDK to use as a Boot JDK

# 2) There are several ways to locate a JDK, that are mostly platform

#    dependent **)

# 3) You can have multiple JDKs installed

# 4) If possible, configure should try to dig out an acceptable JDK

#    automatically, without having to resort to command-line options

#

# *)  acceptable means e.g. JDK7 for building JDK8, a complete JDK (with

#     javac) and not a JRE, etc.

#

# **) On Windows we typically use a well-known path.

#     On MacOSX we typically use the tool java_home.

#     On Linux we typically find javac in the $PATH, and then follow a

#     chain of symlinks that often ends up in a real JDK.

#

# This leads to the code where we check in different ways to locate a

# JDK, and if one is found, check if it is acceptable. If not, we print

# our reasons for rejecting it (useful when debugging non-working

# configure situations) and continue checking the next one.

########################################################################

# Execute the check given as argument, and verify the result

# If the Boot JDK was previously found, do nothing

# $1 A command line (typically autoconf macro) to execute

AC_DEFUN([BOOTJDK_DO_CHECK],

[

  if test "x$BOOT_JDK_FOUND" = xno; then

    # Now execute the test

    $1

    # If previous step claimed to have found a JDK, check it to see if it seems to be valid.

    if test "x$BOOT_JDK_FOUND" = xmaybe; then

      # Do we have a bin/java?

      if test ! -x "$BOOT_JDK/bin/java"; then

        AC_MSG_NOTICE([Potential Boot JDK found at $BOOT_JDK did not contain bin/java; ignoring])

        BOOT_JDK_FOUND=no

      else

        # Do we have a bin/javac?

        if test ! -x "$BOOT_JDK/bin/javac"; then

          AC_MSG_NOTICE([Potential Boot JDK found at $BOOT_JDK did not contain bin/javac; ignoring])

          AC_MSG_NOTICE([(This might be an JRE instead of an JDK)])

          BOOT_JDK_FOUND=no

        else

          # Oh, this is looking good! We probably have found a proper JDK. Is it the correct version?

          BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java" -version 2>&1 | $HEAD -n 1`

          # Extra M4 quote needed to protect [] in grep expression.

          [FOUND_CORRECT_VERSION=`$ECHO $BOOT_JDK_VERSION | $EGREP '\"10([\.+-].*)?\"|\"9([\.+-].*)?\"'`]

          if test "x$FOUND_CORRECT_VERSION" = x; then

            AC_MSG_NOTICE([Potential Boot JDK found at $BOOT_JDK is incorrect JDK version ($BOOT_JDK_VERSION); ignoring])

            AC_MSG_NOTICE([(Your Boot JDK must be version 9 or 10)])

            BOOT_JDK_FOUND=no

          else

            # We're done! :-)

            BOOT_JDK_FOUND=yes

            BASIC_FIXUP_PATH(BOOT_JDK)

            AC_MSG_CHECKING([for Boot JDK])

            AC_MSG_RESULT([$BOOT_JDK])

            AC_MSG_CHECKING([Boot JDK version])

            BOOT_JDK_VERSION=`"$BOOT_JDK/bin/java" -version 2>&1 | $TR '\n\r' '  '`

            AC_MSG_RESULT([$BOOT_JDK_VERSION])

          fi # end check jdk version

        fi # end check javac

      fi # end check java

    fi # end check boot jdk found

  fi

])

# Test: Is bootjdk explicitly set by command line arguments?

AC_DEFUN([BOOTJDK_CHECK_ARGUMENTS],

[

  if test "x$with_boot_jdk" != x; then

    BOOT_JDK=$with_boot_jdk

    BOOT_JDK_FOUND=maybe

    AC_MSG_NOTICE([Found potential Boot JDK using configure arguments])

  fi

])

# Test: Is $JAVA_HOME set?

AC_DEFUN([BOOTJDK_CHECK_JAVA_HOME],

[

  if test "x$JAVA_HOME" != x; then

    JAVA_HOME_PROCESSED="$JAVA_HOME"

    BASIC_FIXUP_PATH(JAVA_HOME_PROCESSED)

    if test ! -d "$JAVA_HOME_PROCESSED"; then

      AC_MSG_NOTICE([Your JAVA_HOME points to a non-existing directory!])

    else

      # Aha, the user has set a JAVA_HOME

      # let us use that as the Boot JDK.

      BOOT_JDK="$JAVA_HOME_PROCESSED"

      BOOT_JDK_FOUND=maybe

      AC_MSG_NOTICE([Found potential Boot JDK using JAVA_HOME])

    fi

  fi

])

# Test: Is there a java or javac in the PATH, which is a symlink to the JDK?

AC_DEFUN([BOOTJDK_CHECK_JAVA_IN_PATH_IS_SYMLINK],

[

  AC_PATH_PROG(JAVAC_CHECK, javac)

  AC_PATH_PROG(JAVA_CHECK, java)

  BINARY="$JAVAC_CHECK"

  if test "x$JAVAC_CHECK" = x; then

    BINARY="$JAVA_CHECK"

  fi

  if test "x$BINARY" != x; then

    # So there is a java(c) binary, it might be part of a JDK.

    # Lets find the JDK/JRE directory by following symbolic links.

    # Linux/GNU systems often have links from /usr/bin/java to

    # /etc/alternatives/java to the real JDK binary.

    BASIC_REMOVE_SYMBOLIC_LINKS(BINARY)

    BOOT_JDK=`dirname "$BINARY"`

    BOOT_JDK=`cd "$BOOT_JDK/.."; pwd`

    if test -x "$BOOT_JDK/bin/javac" && test -x "$BOOT_JDK/bin/java"; then

      # Looks like we found ourselves an JDK

      BOOT_JDK_FOUND=maybe

      AC_MSG_NOTICE([Found potential Boot JDK using java(c) in PATH])

    fi

  fi

])

# Test: Is there a /usr/libexec/java_home? (Typically on MacOSX)

# $1: Argument to the java_home binary (optional)

AC_DEFUN([BOOTJDK_CHECK_LIBEXEC_JAVA_HOME],

[

  if test -x /usr/libexec/java_home; then

    BOOT_JDK=`/usr/libexec/java_home $1`

    BOOT_JDK_FOUND=maybe

    AC_MSG_NOTICE([Found potential Boot JDK using /usr/libexec/java_home $1])

  fi

])

# Test: On MacOS X, can we find a boot jdk using /usr/libexec/java_home?

AC_DEFUN([BOOTJDK_CHECK_MACOSX_JAVA_LOCATOR],

[

  if test "x$OPENJDK_TARGET_OS" = xmacosx; then

    # First check at user selected default

    BOOTJDK_DO_CHECK([BOOTJDK_CHECK_LIBEXEC_JAVA_HOME()])

    # If that did not work out (e.g. too old), try explicit versions instead

    BOOTJDK_DO_CHECK([BOOTJDK_CHECK_LIBEXEC_JAVA_HOME([-v 1.9])])

    BOOTJDK_DO_CHECK([BOOTJDK_CHECK_LIBEXEC_JAVA_HOME([-v 1.8])])

    BOOTJDK_DO_CHECK([BOOTJDK_CHECK_LIBEXEC_JAVA_HOME([-v 1.7])])

  fi

])

# Look for a jdk in the given path. If there are multiple, try to select the newest.

# If found, set BOOT_JDK and BOOT_JDK_FOUND.

# $1 = Path to directory containing jdk installations.

# $2 = String to append to the found JDK directory to get the proper JDK home

AC_DEFUN([BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY],

[

  BOOT_JDK_PREFIX="$1"

  BOOT_JDK_SUFFIX="$2"

  ALL_JDKS_FOUND=`$LS "$BOOT_JDK_PREFIX" 2> /dev/null | $SORT -r`

  if test "x$ALL_JDKS_FOUND" != x; then

    for JDK_TO_TRY in $ALL_JDKS_FOUND ; do

      BOOTJDK_DO_CHECK([

        BOOT_JDK="${BOOT_JDK_PREFIX}/${JDK_TO_TRY}${BOOT_JDK_SUFFIX}"

        if test -d "$BOOT_JDK"; then

          BOOT_JDK_FOUND=maybe

          AC_MSG_NOTICE([Found potential Boot JDK using well-known locations (in $BOOT_JDK_PREFIX/$JDK_TO_TRY)])

        fi

      ])

    done

  fi

])

# Call BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY, but use the given

# environmental variable as base for where to look.

# $1 Name of an environmal variable, assumed to point to the Program Files directory.

AC_DEFUN([BOOTJDK_FIND_BEST_JDK_IN_WINDOWS_VIRTUAL_DIRECTORY],

[

  if test "x[$]$1" != x; then

    VIRTUAL_DIR="[$]$1/Java"

    BASIC_WINDOWS_REWRITE_AS_UNIX_PATH(VIRTUAL_DIR)

    BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY($VIRTUAL_DIR)

  fi

])

# Test: Is there a JDK installed in default, well-known locations?

AC_DEFUN([BOOTJDK_CHECK_WELL_KNOWN_LOCATIONS],

[

  if test "x$OPENJDK_TARGET_OS" = xwindows; then

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_WINDOWS_VIRTUAL_DIRECTORY([ProgramW6432])])

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_WINDOWS_VIRTUAL_DIRECTORY([PROGRAMW6432])])

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_WINDOWS_VIRTUAL_DIRECTORY([PROGRAMFILES])])

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_WINDOWS_VIRTUAL_DIRECTORY([ProgramFiles])])

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY([/cygdrive/c/Program Files/Java])])

  elif test "x$OPENJDK_TARGET_OS" = xmacosx; then

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY([/Library/Java/JavaVirtualMachines],[/Contents/Home])])

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY([/System/Library/Java/JavaVirtualMachines],[/Contents/Home])])

  elif test "x$OPENJDK_TARGET_OS" = xlinux; then

    BOOTJDK_DO_CHECK([BOOTJDK_FIND_BEST_JDK_IN_DIRECTORY([/usr/lib/jvm])])

  fi

])

# Check that a command-line tool in the Boot JDK is correct

# $1 = name of variable to assign

# $2 = name of binary

AC_DEFUN([BOOTJDK_CHECK_TOOL_IN_BOOTJDK],

[

  # Use user overridden value if available, otherwise locate tool in the Boot JDK.

  BASIC_SETUP_TOOL($1,

    [

      AC_MSG_CHECKING([for $2 in Boot JDK])

      $1=$BOOT_JDK/bin/$2

      if test ! -x [$]$1; then

        AC_MSG_RESULT(not found)

        AC_MSG_NOTICE([Your Boot JDK seems broken. This might be fixed by explicitly setting --with-boot-jdk])

        AC_MSG_ERROR([Could not find $2 in the Boot JDK])

      fi

      AC_MSG_RESULT(ok)

      AC_SUBST($1)

    ])

])

###############################################################################

#

# We need a Boot JDK to bootstrap the build.

#

AC_DEFUN_ONCE([BOOTJDK_SETUP_BOOT_JDK],

[

  BOOT_JDK_FOUND=no

  AC_ARG_WITH(boot-jdk, [AS_HELP_STRING([--with-boot-jdk],

      [path to Boot JDK (used to bootstrap build) @<:@probed@:>@])])

  # We look for the Boot JDK through various means, going from more certain to

  # more of a guess-work. After each test, BOOT_JDK_FOUND is set to "yes" if

  # we detected something (if so, the path to the jdk is in BOOT_JDK). But we

  # must check if this is indeed valid; otherwise we'll continue looking.

  # Test: Is bootjdk explicitly set by command line arguments?

  BOOTJDK_DO_CHECK([BOOTJDK_CHECK_ARGUMENTS])

  if test "x$with_boot_jdk" != x && test "x$BOOT_JDK_FOUND" = xno; then

    # Having specified an argument which is incorrect will produce an instant failure;

    # we should not go on looking

    AC_MSG_ERROR([The path given by --with-boot-jdk does not contain a valid Boot JDK])

  fi

  # Test: On MacOS X, can we find a boot jdk using /usr/libexec/java_home?

  BOOTJDK_DO_CHECK([BOOTJDK_CHECK_MACOSX_JAVA_LOCATOR])

  # Test: Is $JAVA_HOME set?

  BOOTJDK_DO_CHECK([BOOTJDK_CHECK_JAVA_HOME])

  # Test: Is there a java or javac in the PATH, which is a symlink to the JDK?

  BOOTJDK_DO_CHECK([BOOTJDK_CHECK_JAVA_IN_PATH_IS_SYMLINK])

  # Test: Is there a JDK installed in default, well-known locations?

  BOOTJDK_DO_CHECK([BOOTJDK_CHECK_WELL_KNOWN_LOCATIONS])

  # If we haven't found anything yet, we've truly lost. Give up.

  if test "x$BOOT_JDK_FOUND" = xno; then

    HELP_MSG_MISSING_DEPENDENCY([openjdk])

    AC_MSG_NOTICE([Could not find a valid Boot JDK. $HELP_MSG])

    AC_MSG_NOTICE([This might be fixed by explicitly setting --with-boot-jdk])

    AC_MSG_ERROR([Cannot continue])

  fi

  AC_SUBST(BOOT_JDK)

  # Setup tools from the Boot JDK.

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVA, java)

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVAC, javac)

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVAH, javah)

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAVADOC, javadoc)

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JAR, jar)

  BOOTJDK_CHECK_TOOL_IN_BOOTJDK(JARSIGNER, jarsigner)

  # Finally, set some other options...

  # When compiling code to be executed by the Boot JDK, force compatibility with the

  # oldest supported bootjdk.

  BOOT_JDK_SOURCETARGET="-source 9 -target 9"

  AC_SUBST(BOOT_JDK_SOURCETARGET)

  AC_SUBST(JAVAC_FLAGS)

  # Check if the boot jdk is 32 or 64 bit

  if "$JAVA" -version 2>&1 | $GREP -q "64-Bit"; then

    BOOT_JDK_BITS="64"

  else

    BOOT_JDK_BITS="32"

  fi

  AC_MSG_CHECKING([if Boot JDK is 32 or 64 bits])

  AC_MSG_RESULT([$BOOT_JDK_BITS])

  # Try to enable CDS

  AC_MSG_CHECKING([for local Boot JDK Class Data Sharing (CDS)])

  BOOT_JDK_CDS_ARCHIVE=$CONFIGURESUPPORT_OUTPUTDIR/classes.jsa

  ADD_JVM_ARG_IF_OK([-XX:+UnlockDiagnosticVMOptions -XX:-VerifySharedSpaces -XX:SharedArchiveFile=$BOOT_JDK_CDS_ARCHIVE],boot_jdk_cds_args,[$JAVA])

  if test "x$boot_jdk_cds_args" != x; then

    # Try creating a CDS archive

    "$JAVA" $boot_jdk_cds_args -Xshare:dump > /dev/null 2>&1

    if test $? -eq 0; then

      BOOTJDK_USE_LOCAL_CDS=true

      AC_MSG_RESULT([yes, created])

    else

      # Generation failed, don't use CDS.

      BOOTJDK_USE_LOCAL_CDS=false

      AC_MSG_RESULT([no, creation failed])

    fi

  else

    BOOTJDK_USE_LOCAL_CDS=false

    AC_MSG_RESULT([no, -XX:SharedArchiveFile not supported])

  fi

])

AC_DEFUN_ONCE([BOOTJDK_SETUP_BOOT_JDK_ARGUMENTS],

[

  ##############################################################################

  #

  # Specify jvm options for anything that is run with the Boot JDK.

  # Not all JVM:s accept the same arguments on the command line.

  #

  AC_ARG_WITH(boot-jdk-jvmargs, [AS_HELP_STRING([--with-boot-jdk-jvmargs],

  [specify JVM arguments to be passed to all java invocations of boot JDK, overriding the default values,

  e.g --with-boot-jdk-jvmargs="-Xmx8G -enableassertions"])])

  AC_MSG_CHECKING([flags for boot jdk java command] )

  # Force en-US environment

  ADD_JVM_ARG_IF_OK([-Duser.language=en -Duser.country=US],boot_jdk_jvmargs,[$JAVA])

  if test "x$BOOTJDK_USE_LOCAL_CDS" = xtrue; then

    # Use our own CDS archive

    ADD_JVM_ARG_IF_OK([$boot_jdk_cds_args -Xshare:auto],boot_jdk_jvmargs,[$JAVA])

  else

    # Otherwise optimistically use the system-wide one, if one is present

    ADD_JVM_ARG_IF_OK([-Xshare:auto],boot_jdk_jvmargs,[$JAVA])

  fi

  # Apply user provided options.

  ADD_JVM_ARG_IF_OK([$with_boot_jdk_jvmargs],boot_jdk_jvmargs,[$JAVA])

  AC_MSG_RESULT([$boot_jdk_jvmargs])

  # For now, general JAVA_FLAGS are the same as the boot jdk jvmargs

  JAVA_FLAGS=$boot_jdk_jvmargs

  AC_SUBST(JAVA_FLAGS)

  AC_MSG_CHECKING([flags for boot jdk java command for big workloads])

  # Starting amount of heap memory.

  ADD_JVM_ARG_IF_OK([-Xms64M],boot_jdk_jvmargs_big,[$JAVA])

  BOOTCYCLE_JVM_ARGS_BIG=-Xms64M

  # Maximum amount of heap memory and stack size.

  JVM_HEAP_LIMIT_32="1024"

  # Running a 64 bit JVM allows for and requires a bigger heap

  JVM_HEAP_LIMIT_64="1600"

  STACK_SIZE_32=768

  STACK_SIZE_64=1536

  JVM_HEAP_LIMIT_GLOBAL=`expr $MEMORY_SIZE / 2`

  if test "$JVM_HEAP_LIMIT_GLOBAL" -lt "$JVM_HEAP_LIMIT_32"; then

    JVM_HEAP_LIMIT_32=$JVM_HEAP_LIMIT_GLOBAL

  fi

  if test "$JVM_HEAP_LIMIT_GLOBAL" -lt "$JVM_HEAP_LIMIT_64"; then

    JVM_HEAP_LIMIT_64=$JVM_HEAP_LIMIT_GLOBAL

  fi

  if test "$JVM_HEAP_LIMIT_GLOBAL" -lt "512"; then

    JVM_HEAP_LIMIT_32=512

    JVM_HEAP_LIMIT_64=512

  fi

  if test "x$BOOT_JDK_BITS" = "x32"; then

    STACK_SIZE=$STACK_SIZE_32

    JVM_MAX_HEAP=$JVM_HEAP_LIMIT_32

  else

    STACK_SIZE=$STACK_SIZE_64

    JVM_MAX_HEAP=$JVM_HEAP_LIMIT_64

  fi

  ADD_JVM_ARG_IF_OK([-Xmx${JVM_MAX_HEAP}M],boot_jdk_jvmargs_big,[$JAVA])

  ADD_JVM_ARG_IF_OK([-XX:ThreadStackSize=$STACK_SIZE],boot_jdk_jvmargs_big,[$JAVA])

  AC_MSG_RESULT([$boot_jdk_jvmargs_big])

  JAVA_FLAGS_BIG=$boot_jdk_jvmargs_big

  AC_SUBST(JAVA_FLAGS_BIG)

  if test "x$OPENJDK_TARGET_CPU_BITS" = "x32"; then

    BOOTCYCLE_MAX_HEAP=$JVM_HEAP_LIMIT_32

    BOOTCYCLE_STACK_SIZE=$STACK_SIZE_32

  else

    BOOTCYCLE_MAX_HEAP=$JVM_HEAP_LIMIT_64

    BOOTCYCLE_STACK_SIZE=$STACK_SIZE_64

  fi

  BOOTCYCLE_JVM_ARGS_BIG="$BOOTCYCLE_JVM_ARGS_BIG -Xmx${BOOTCYCLE_MAX_HEAP}M"

  BOOTCYCLE_JVM_ARGS_BIG="$BOOTCYCLE_JVM_ARGS_BIG -XX:ThreadStackSize=$BOOTCYCLE_STACK_SIZE"

  AC_MSG_CHECKING([flags for bootcycle boot jdk java command for big workloads])

  AC_MSG_RESULT([$BOOTCYCLE_JVM_ARGS_BIG])

  AC_SUBST(BOOTCYCLE_JVM_ARGS_BIG)

  # By default, the main javac compilations use big

  JAVA_FLAGS_JAVAC="$JAVA_FLAGS_BIG"

  AC_SUBST(JAVA_FLAGS_JAVAC)

  AC_MSG_CHECKING([flags for boot jdk java command for small workloads])

  # Use serial gc for small short lived tools if possible

  ADD_JVM_ARG_IF_OK([-XX:+UseSerialGC],boot_jdk_jvmargs_small,[$JAVA])

  ADD_JVM_ARG_IF_OK([-Xms32M],boot_jdk_jvmargs_small,[$JAVA])

  ADD_JVM_ARG_IF_OK([-Xmx512M],boot_jdk_jvmargs_small,[$JAVA])

  ADD_JVM_ARG_IF_OK([-XX:TieredStopAtLevel=1],boot_jdk_jvmargs_small,[$JAVA])

  AC_MSG_RESULT([$boot_jdk_jvmargs_small])

  JAVA_FLAGS_SMALL=$boot_jdk_jvmargs_small

  AC_SUBST(JAVA_FLAGS_SMALL)

  JAVA_TOOL_FLAGS_SMALL=""

  for f in $JAVA_FLAGS_SMALL; do

    JAVA_TOOL_FLAGS_SMALL="$JAVA_TOOL_FLAGS_SMALL -J$f"

  done

  AC_SUBST(JAVA_TOOL_FLAGS_SMALL)

])

# BUILD_JDK: the location of the latest JDK that can run

#   on the host system and supports the target class file version

#   generated in this JDK build.  This variable should only be

#   used after the launchers are built.

#

# Execute the check given as argument, and verify the result.

# If the JDK was previously found, do nothing.

# $1 A command line (typically autoconf macro) to execute

AC_DEFUN([BOOTJDK_CHECK_BUILD_JDK],

[

  if test "x$BUILD_JDK_FOUND" = xno; then

    # Execute the test

    $1

    # If previous step claimed to have found a JDK, check it to see if it seems to be valid.

    if test "x$BUILD_JDK_FOUND" = xmaybe; then

      # Do we have a bin/java?

      if test ! -x "$BUILD_JDK/bin/java"; then

        AC_MSG_NOTICE([Potential Build JDK found at $BUILD_JDK did not contain bin/java; ignoring])

        BUILD_JDK_FOUND=no

      elif test ! -x "$BUILD_JDK/bin/jlink"; then

        AC_MSG_NOTICE([Potential Build JDK found at $BUILD_JDK did not contain bin/jlink; ignoring])

        BUILD_JDK_FOUND=no

      elif test ! -x "$BUILD_JDK/bin/jmod"; then

        AC_MSG_NOTICE([Potential Build JDK found at $BUILD_JDK did not contain bin/jmod; ignoring])

        BUILD_JDK_FOUND=no

      elif test ! -x "$BUILD_JDK/bin/javac"; then

        # Do we have a bin/javac?

        AC_MSG_NOTICE([Potential Build JDK found at $BUILD_JDK did not contain bin/javac; ignoring])

        AC_MSG_NOTICE([(This might be a JRE instead of an JDK)])

        BUILD_JDK_FOUND=no

      else

        # Oh, this is looking good! We probably have found a proper JDK. Is it the correct version?

        BUILD_JDK_VERSION=`"$BUILD_JDK/bin/java" -version 2>&1 | $HEAD -n 1`

        # Extra M4 quote needed to protect [] in grep expression.

        [FOUND_CORRECT_VERSION=`echo $BUILD_JDK_VERSION | $EGREP '\"10([\.+-].*)?\"'`]