util.m4

#
# Copyright (c) 2011, 2020, 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.
#

m4_include([util_paths.m4])
m4_include([util_windows.m4])

###############################################################################
# Create a function/macro that takes a series of named arguments. The call is
# similar to AC_DEFUN, but the setup of the function looks like this:
# UTIL_DEFUN_NAMED([MYFUNC], [FOO *BAR], [$@], [
# ... do something
#   AC_MSG_NOTICE([Value of BAR is ARG_BAR])
# ])
# A star (*) in front of a named argument means that it is required and it's
# presence will be verified. To pass e.g. the first value as a normal indexed
# argument, use [m4_shift($@)] as the third argument instead of [$@]. These
# arguments are referenced in the function by their name prefixed by ARG_, e.g.
# "ARG_FOO".
#
# The generated function can be called like this:
# MYFUNC(FOO: [foo-val],
#     BAR: [
#         $ECHO hello world
#     ])
# Note that the argument value must start on the same line as the argument name.
#
# Argument 1: Name of the function to define
# Argument 2: List of legal named arguments, with a * prefix for required arguments
# Argument 3: Argument array to treat as named, typically $@
# Argument 4: The main function body
AC_DEFUN([UTIL_DEFUN_NAMED],
[
  AC_DEFUN($1, [
    m4_foreach(arg, m4_split(m4_normalize($2)), [
      m4_if(m4_bregexp(arg, [^\*]), -1,
        [
          m4_set_add(legal_named_args, arg)
        ],
        [
          m4_set_add(legal_named_args, m4_substr(arg, 1))
          m4_set_add(required_named_args, m4_substr(arg, 1))
        ]
      )
    ])

    m4_foreach([arg], [$3], [
      m4_if(m4_bregexp(arg, [: ]), -1, m4_define([arg], m4_bpatsubst(arg, [:], [: ])))
      m4_define(arg_name, m4_substr(arg, 0, m4_bregexp(arg, [: ])))
      m4_set_contains(legal_named_args, arg_name, [],[AC_MSG_ERROR([Internal error: m4_if(arg_name, , arg, arg_name) is not a valid named argument to [$1]. Valid arguments are 'm4_set_contents(defined_args, [ ]) m4_set_contents(legal_named_args, [ ])'.])])
      m4_set_remove(required_named_args, arg_name)
      m4_set_remove(legal_named_args, arg_name)
      m4_pushdef([ARG_][]arg_name, m4_bpatsubst(m4_substr(arg, m4_incr(m4_incr(m4_bregexp(arg, [: ])))), [^\s*], []))
      m4_set_add(defined_args, arg_name)
      m4_undefine([arg_name])
    ])
    m4_set_empty(required_named_args, [], [
      AC_MSG_ERROR([Internal error: Required named arguments are missing for [$1]. Missing arguments: 'm4_set_contents(required_named_args, [ ])'])
    ])
    m4_foreach([arg], m4_indir([m4_dquote]m4_set_listc([legal_named_args])), [
      m4_pushdef([ARG_][]arg, [])
      m4_set_add(defined_args, arg)
    ])
    m4_set_delete(legal_named_args)
    m4_set_delete(required_named_args)

    # Execute function body
    $4

    m4_foreach([arg], m4_indir([m4_dquote]m4_set_listc([defined_args])), [
      m4_popdef([ARG_][]arg)
    ])

    m4_set_delete(defined_args)
  ])
])

###############################################################################
# Assert that a programmatic condition holds. If not, exit with an error message.
# Check that a shell expression gives return code 0
#
# $1: The shell expression to evaluate
# $2: A message to describe the expression in case of failure
# $2: An message to print in case of failure [optional]
#
AC_DEFUN([UTIL_ASSERT_SHELL_TEST],
[
  ASSERTION_MSG="m4_normalize([$3])"
  if $1; then
    $ECHO Assertion failed: $2
    if test "x$3" != x; then
      $ECHO Assertion message: "$3"
    fi
    exit 1
  fi
])


###############################################################################
# Assert that a programmatic condition holds. If not, exit with an error message.
# Check that two strings are equal.
#
# $1: The actual string found
# $2: The expected string
# $3: An message to print in case of failure [optional]
#
AC_DEFUN([UTIL_ASSERT_STRING_EQUALS],
[
  UTIL_ASSERT_SHELL_TEST(
      [test "x[$1]" != "x[$2]"],
      [Actual value '[$1]' \("[$1]"\) did not match expected value '[$2]' \("[$2]"\)],
      $3)
])

###############################################################################
# Assert that a programmatic condition holds. If not, exit with an error message.
# Check that two strings not are equal.
#
# $1: The actual string found
# $2: The expected string
# $3: An message to print in case of failure [optional]
#
AC_DEFUN([UTIL_ASSERT_STRING_NOT_EQUALS],
[
  UTIL_ASSERT_SHELL_TEST(
      [test "x[$1]" = "x[$2]"],
      [Actual value '[$1]' \("[$1]"\) unexpectedly matched '[$2]' \("[$2]"\)],
      $3)
])

###############################################################################
# Assert that a programmatic condition holds. If not, exit with an error message.
# Check that the given expression evaluates to the string 'true'
#
# $1: The expression to evaluate
# $2: An message to print in case of failure [optional]
#
AC_DEFUN([UTIL_ASSERT_TRUE],
[
  UTIL_ASSERT_STRING_EQUALS($1, true, $3)
])

###############################################################################
# Assert that a programmatic condition holds. If not, exit with an error message.
# Check that the given expression does not evaluate to the string 'true'
#
# $1: The expression to evaluate
# $2: An message to print in case of failure [optional]
#
AC_DEFUN([UTIL_ASSERT_NOT_TRUE],
[
  UTIL_ASSERT_STRING_NOT_EQUALS($1, true, $3)
])

###############################################################################
# Check if a list of space-separated words are selected only from a list of
# space-separated legal words. Typical use is to see if a user-specified
# set of words is selected from a set of legal words.
#
# Sets the specified variable to list of non-matching (offending) words, or to
# the empty string if all words are matching the legal set.
#
# $1: result variable name
# $2: list of values to check
# $3: list of legal values
AC_DEFUN([UTIL_GET_NON_MATCHING_VALUES],
[
  # grep filter function inspired by a comment to http://stackoverflow.com/a/1617326
  # Notice that the original variant fails on SLES 10 and 11
  # Some grep versions (at least bsd) behaves strangely on the base case with
  # no legal_values, so make it explicit.
  values_to_check=`$ECHO $2 | $TR ' ' '\n'`
  legal_values=`$ECHO $3 | $TR ' ' '\n'`
  if test -z "$legal_values"; then
    $1="$2"
  else
    result=`$GREP -Fvx "$legal_values" <<< "$values_to_check" | $GREP -v '^$'`
    $1=${result//$'\n'/ }
  fi
])

###############################################################################
# Check if a list of space-separated words contains any word(s) from a list of
# space-separated illegal words. Typical use is to see if a user-specified
# set of words contains any from a set of illegal words.
#
# Sets the specified variable to list of matching illegal words, or to
# the empty string if no words are matching the illegal set.
#
# $1: result variable name
# $2: list of values to check
# $3: list of illegal values
AC_DEFUN([UTIL_GET_MATCHING_VALUES],
[
  # grep filter function inspired by a comment to http://stackoverflow.com/a/1617326
  # Notice that the original variant fails on SLES 10 and 11
  # Some grep versions (at least bsd) behaves strangely on the base case with
  # no legal_values, so make it explicit.
  values_to_check=`$ECHO $2 | $TR ' ' '\n'`
  illegal_values=`$ECHO $3 | $TR ' ' '\n'`
  if test -z "$illegal_values"; then
    $1=""
  else
    result=`$GREP -Fx "$illegal_values" <<< "$values_to_check" | $GREP -v '^$'`
    $1=${result//$'\n'/ }
  fi
])

###############################################################################
# Converts an ISO-8601 date/time string to a unix epoch timestamp. If no
# suitable conversion method was found, an empty string is returned.
#
# Sets the specified variable to the resulting list.
#
# $1: result variable name
# $2: input date/time string
AC_DEFUN([UTIL_GET_EPOCH_TIMESTAMP],
[
  timestamp=$($DATE --utc --date=$2 +"%s" 2> /dev/null)
  if test "x$timestamp" = x; then
    # GNU date format did not work, try BSD date options
    timestamp=$($DATE -j -f "%F %T" "$2" "+%s" 2> /dev/null)
    if test "x$timestamp" = x; then
      # Perhaps the time was missing
      timestamp=$($DATE -j -f "%F %T" "$2 00:00:00" "+%s" 2> /dev/null)
      # If this did not work, we give up and return the empty string
    fi
  fi
  $1=$timestamp
])

###############################################################################
# Sort a space-separated list, and remove duplicates.
#
# Sets the specified variable to the resulting list.
#
# $1: result variable name
# $2: list of values to sort
AC_DEFUN([UTIL_SORT_LIST],
[
  values_to_sort=`$ECHO $2 | $TR ' ' '\n'`
  result=`$SORT -u <<< "$values_to_sort" | $GREP -v '^$'`
  $1=${result//$'\n'/ }
])

###############################################################################
# Test if $1 is a valid argument to $3 (often is $JAVA passed as $3)
# If so, then append $1 to $2 \
# Also set JVM_ARG_OK to true/false depending on outcome.
AC_DEFUN([UTIL_ADD_JVM_ARG_IF_OK],
[
  $ECHO "Check if jvm arg is ok: $1" >&AS_MESSAGE_LOG_FD
  $ECHO "Command: $3 $1 -version" >&AS_MESSAGE_LOG_FD
  OUTPUT=`$3 $1 $USER_BOOT_JDK_OPTIONS -version 2>&1`
  FOUND_WARN=`$ECHO "$OUTPUT" | $GREP -i warn`
  FOUND_VERSION=`$ECHO $OUTPUT | $GREP " version \""`
  if test "x$FOUND_VERSION" != x && test "x$FOUND_WARN" = x; then
    $2="[$]$2 $1"
    JVM_ARG_OK=true
  else
    $ECHO "Arg failed:" >&AS_MESSAGE_LOG_FD
    $ECHO "$OUTPUT" >&AS_MESSAGE_LOG_FD
    JVM_ARG_OK=false
  fi
])

###############################################################################
# Register a --with argument but mark it as deprecated
# $1: The name of the with argument to deprecate, not including --with-
AC_DEFUN([UTIL_DEPRECATED_ARG_WITH],
[
  AC_ARG_WITH($1, [AS_HELP_STRING([--with-$1],
      [Deprecated. Option is kept for backwards compatibility and is ignored])],
      [AC_MSG_WARN([Option --with-$1 is deprecated and will be ignored.])])
])

###############################################################################
# Register a --enable argument but mark it as deprecated
# $1: The name of the with argument to deprecate, not including --enable-
AC_DEFUN([UTIL_DEPRECATED_ARG_ENABLE],
[
  AC_ARG_ENABLE($1, [AS_HELP_STRING([--enable-$1],
      [Deprecated. Option is kept for backwards compatibility and is ignored])],
      [AC_MSG_WARN([Option --enable-$1 is deprecated and will be ignored.])])
])

###############################################################################
# Register an --enable-* argument as an alias for another argument.
# $1: The name of the enable argument for the new alias, not including --enable-
# $2: The full name of the argument of which to make this an alias, including
#     --enable- or --with-.
AC_DEFUN([UTIL_ALIASED_ARG_ENABLE],
[
  AC_ARG_ENABLE($1, [AS_HELP_STRING([--enable-$1], [alias for $2])], [
    # Use m4 to strip initial -- from target ($2), convert - to _, prefix enable_
    # to new alias name, and create a shell variable assignment,
    # e.g.: enable_old_style="$enable_new_alias"
    m4_translit(m4_bpatsubst($2, --), -, _)="$[enable_]m4_translit($1, -, _)"
  ])
])

###############################################################################
# Creates a command-line option using the --enable-* pattern. Will return a
# value of 'true' or 'false' in the RESULT variable, depending on whether the
# option was enabled or not by the user. The option can not be turned on if it
# is not available, as specified by AVAILABLE and/or AVAILABLE_CHECK.
#
# Arguments:
#   NAME: The base name of this option (i.e. what follows --enable-). Required.
#   RESULT: The name of the variable to set to the result. Defaults to
#     <NAME in uppercase>_RESULT.
#   DEFAULT: The default value for this option. Can be true, false or auto.
#     Defaults to true.
#   AVAILABLE: If true, this option is allowed to be selected. Defaults to true.
#   DESC: A description of this option. Defaults to a generic and unhelpful
#     string.
#   DEFAULT_DESC: A message describing the default value, for the help. Defaults
#     to the literal value of DEFAULT.
#   CHECKING_MSG: The message to present to user when checking this option.
#     Defaults to a generic message.
#   CHECK_AVAILABLE: An optional code block to execute to determine if the
#     option should be available. Must set AVAILABLE to 'false' if not.
#   IF_GIVEN:  An optional code block to execute if the option was given on the
#     command line (regardless of the value).
#   IF_NOT_GIVEN:  An optional code block to execute if the option was not given
#     on the command line (regardless of the value).
#   IF_ENABLED:  An optional code block to execute if the option is turned on.
#   IF_DISABLED:  An optional code block to execute if the option is turned off.
#
UTIL_DEFUN_NAMED([UTIL_ARG_ENABLE],
    [*NAME RESULT DEFAULT AVAILABLE DESC DEFAULT_DESC CHECKING_MSG
    CHECK_AVAILABLE IF_GIVEN IF_NOT_GIVEN IF_ENABLED IF_DISABLED], [$@],
[
  ##########################
  # Part 1: Set up m4 macros
  ##########################

  # If DEFAULT is not specified, set it to 'true'.
  m4_define([ARG_DEFAULT], m4_if(ARG_DEFAULT, , true, ARG_DEFAULT))

  # If AVAILABLE is not specified, set it to 'true'.
  m4_define([ARG_AVAILABLE], m4_if(ARG_AVAILABLE, , true, ARG_AVAILABLE))

  # If DEFAULT_DESC is not specified, calculate it from DEFAULT.
  m4_define([ARG_DEFAULT_DESC], m4_if(ARG_DEFAULT_DESC, , m4_if(ARG_DEFAULT, true, enabled, m4_if(ARG_DEFAULT, false, disabled, ARG_DEFAULT)), ARG_DEFAULT_DESC))

  # If RESULT is not specified, set it to 'ARG_NAME[_ENABLED]'.
  m4_define([ARG_RESULT], m4_if(ARG_RESULT, , m4_translit(ARG_NAME, [a-z-], [A-Z_])[_ENABLED], ARG_RESULT))
  # Construct shell variable names for the option
  m4_define(ARG_OPTION, [enable_]m4_translit(ARG_NAME, [-], [_]))
  m4_define(ARG_GIVEN, m4_translit(ARG_NAME, [a-z-], [A-Z_])[_GIVEN])

  # If DESC is not specified, set it to a generic description.
  m4_define([ARG_DESC], m4_if(ARG_DESC, , [Enable the ARG_NAME feature], m4_normalize(ARG_DESC)))

  # If CHECKING_MSG is not specified, set it to a generic description.
  m4_define([ARG_CHECKING_MSG], m4_if(ARG_CHECKING_MSG, , [for --enable-ARG_NAME], ARG_CHECKING_MSG))

  # If the code blocks are not given, set them to the empty statements to avoid
  # tripping up bash.
  m4_define([ARG_CHECK_AVAILABLE], m4_if(ARG_CHECK_AVAILABLE, , :, ARG_CHECK_AVAILABLE))
  m4_define([ARG_IF_GIVEN], m4_if(ARG_IF_GIVEN, , :, ARG_IF_GIVEN))
  m4_define([ARG_IF_NOT_GIVEN], m4_if(ARG_IF_NOT_GIVEN, , :, ARG_IF_NOT_GIVEN))
  m4_define([ARG_IF_ENABLED], m4_if(ARG_IF_ENABLED, , :, ARG_IF_ENABLED))
  m4_define([ARG_IF_DISABLED], m4_if(ARG_IF_DISABLED, , :, ARG_IF_DISABLED))

  ##########################
  # Part 2: Set up autoconf shell code
  ##########################

  # Check that DEFAULT has a valid value
  if test "[x]ARG_DEFAULT" != xtrue && test "[x]ARG_DEFAULT" != xfalse && \
      test "[x]ARG_DEFAULT" != xauto ; then
    AC_MSG_ERROR([Internal error: Argument DEFAULT to [UTIL_ARG_ENABLE] can only be true, false or auto, was: 'ARG_DEFAULT'])
  fi

  # Check that AVAILABLE has a valid value
  if test "[x]ARG_AVAILABLE" != xtrue && test "[x]ARG_AVAILABLE" != xfalse; then
    AC_MSG_ERROR([Internal error: Argument AVAILABLE to [UTIL_ARG_ENABLE] can only be true or false, was: 'ARG_AVAILABLE'])
  fi

  AC_ARG_ENABLE(ARG_NAME, AS_HELP_STRING([--enable-]ARG_NAME,
      [ARG_DESC [ARG_DEFAULT_DESC]]), [ARG_GIVEN=true], [ARG_GIVEN=false])

  # Check if the option is available
  AVAILABLE=ARG_AVAILABLE
  # Run the available check block (if any), which can overwrite AVAILABLE.
  ARG_CHECK_AVAILABLE

  # Check if the option should be turned on
  AC_MSG_CHECKING(ARG_CHECKING_MSG)
  if test x$ARG_GIVEN = xfalse; then
    if test ARG_DEFAULT = auto; then
      # If not given, and default is auto, set it to true iff it's available.
      ARG_RESULT=$AVAILABLE
      REASON="from default 'auto'"
    else
      ARG_RESULT=ARG_DEFAULT
      REASON="default"
    fi
  else
    if test x$ARG_OPTION = xyes; then
      ARG_RESULT=true
      REASON="from command line"
    elif test x$ARG_OPTION = xno; then
      ARG_RESULT=false
      REASON="from command line"
    elif test x$ARG_OPTION = xauto; then
      if test ARG_DEFAULT = auto; then
        # If both given and default is auto, set it to true iff it's available.
        ARG_RESULT=$AVAILABLE
      else
        ARG_RESULT=ARG_DEFAULT
      fi
      REASON="from command line 'auto'"
    else
      AC_MSG_ERROR([Option [--enable-]ARG_NAME can only be 'yes', 'no' or 'auto'])
    fi
  fi

  if test x$ARG_RESULT = xtrue; then
    AC_MSG_RESULT([enabled, $REASON])
    if test x$AVAILABLE = xfalse; then
      AC_MSG_ERROR([Option [--enable-]ARG_NAME is not available])
    fi
  else
    AC_MSG_RESULT([disabled, $REASON])
  fi

  # Execute result payloads, if present
  if test x$ARG_GIVEN = xtrue; then
    ARG_IF_GIVEN
  else
    ARG_IF_NOT_GIVEN
  fi

  if test x$ARG_RESULT = xtrue; then
    ARG_IF_ENABLED
  else
    ARG_IF_DISABLED
  fi
])

###############################################################################
# Test that variable $1 denoting a program is not empty. If empty, exit with an error.
# $1: variable to check
AC_DEFUN([UTIL_CHECK_NONEMPTY],
[
  if test "x[$]$1" = x; then
    AC_MSG_ERROR([Could not find required tool for $1])
  fi
])

###############################################################################
# Setup a tool for the given variable. If correctly specified by the user,
# use that value, otherwise search for the tool using the supplied code snippet.
# $1: variable to set
# $2: code snippet to call to look for the tool
# $3: code snippet to call if variable was used to find tool
AC_DEFUN([UTIL_SETUP_TOOL],
[
  # Publish this variable in the help.
  AC_ARG_VAR($1, [Override default value for $1])

  if [[ -z "${$1+x}" ]]; then
    # The variable is not set by user, try to locate tool using the code snippet
    $2
  else
    # The variable is set, but is it from the command line or the environment?

    # Try to remove the string !$1! from our list.
    try_remove_var=${CONFIGURE_OVERRIDDEN_VARIABLES//!$1!/}
    if test "x$try_remove_var" = "x$CONFIGURE_OVERRIDDEN_VARIABLES"; then
      # If it failed, the variable was not from the command line. Ignore it,
      # but warn the user (except for BASH, which is always set by the calling BASH).
      if test "x$1" != xBASH; then
        AC_MSG_WARN([Ignoring value of $1 from the environment. Use command line variables instead.])
      fi
      # Try to locate tool using the code snippet
      $2
    else
      # If it succeeded, then it was overridden by the user. We will use it
      # for the tool.

      # First remove it from the list of overridden variables, so we can test
      # for unknown variables in the end.
      CONFIGURE_OVERRIDDEN_VARIABLES="$try_remove_var"

      tool_override=[$]$1
      AC_MSG_NOTICE([User supplied override $1="$tool_override"])

      # Check if we try to supply an empty value
      if test "x$tool_override" = x; then
        AC_MSG_CHECKING([for $1])
        AC_MSG_RESULT([disabled])
      else
        # Split up override in command part and argument part
        tool_and_args=($tool_override)
        [ tool_command=${tool_and_args[0]} ]
        [ unset 'tool_and_args[0]' ]
        [ tool_args=${tool_and_args[@]} ]

        # Check if the provided tool contains a complete path.
        tool_basename="${tool_command##*/}"
        if test "x$tool_basename" = "x$tool_command"; then
          # A command without a complete path is provided, search $PATH.
          AC_MSG_NOTICE([Will search for user supplied tool "$tool_basename"])
          AC_PATH_PROG($1, $tool_basename)
          if test "x[$]$1" = x; then
            AC_MSG_ERROR([User supplied tool $1="$tool_basename" could not be found])
          fi
        else
          # Otherwise we believe it is a complete path. Use it as it is.
          AC_MSG_NOTICE([Will use user supplied tool "$tool_command"])
          AC_MSG_CHECKING([for $tool_command])
          if test ! -x "$tool_command" && test ! -x "$tool_command.exe"; then
            AC_MSG_RESULT([not found])
            AC_MSG_ERROR([User supplied tool $1="$tool_command" does not exist or is not executable])
          fi
           $1="$tool_command"
          AC_MSG_RESULT([found])
        fi
        if test "x$tool_args" != x; then
          # If we got arguments, re-append them to the command after the fixup.
          $1="[$]$1 $tool_args"
        fi
      fi
    fi
    $3
  fi
])

###############################################################################
# Call UTIL_SETUP_TOOL with AC_PATH_PROGS to locate the tool
# $1: variable to set
# $2: executable name (or list of names) to look for
# $3: [path]
AC_DEFUN([UTIL_PATH_PROGS],
[
  UTIL_SETUP_TOOL($1, [AC_PATH_PROGS($1, $2, , $3)])
])

###############################################################################
# Call UTIL_SETUP_TOOL with AC_CHECK_TOOLS to locate the tool
# $1: variable to set
# $2: executable name (or list of names) to look for
AC_DEFUN([UTIL_CHECK_TOOLS],
[
  UTIL_SETUP_TOOL($1, [AC_CHECK_TOOLS($1, $2)])
])

###############################################################################
# Like UTIL_PATH_PROGS but fails if no tool was found.
# $1: variable to set
# $2: executable name (or list of names) to look for
# $3: [path]
AC_DEFUN([UTIL_REQUIRE_PROGS],
[
  UTIL_PATH_PROGS($1, $2, , $3)
  UTIL_CHECK_NONEMPTY($1)
])

###############################################################################
# Like UTIL_SETUP_TOOL but fails if no tool was found.
# $1: variable to set
# $2: autoconf macro to call to look for the special tool
AC_DEFUN([UTIL_REQUIRE_SPECIAL],
[
  UTIL_SETUP_TOOL($1, [$2])
  UTIL_CHECK_NONEMPTY($1)
])

###############################################################################
# Like UTIL_REQUIRE_PROGS but also allows for bash built-ins
# $1: variable to set
# $2: executable name (or list of names) to look for
# $3: [path]
AC_DEFUN([UTIL_REQUIRE_BUILTIN_PROGS],
[
  UTIL_SETUP_TOOL($1, [AC_PATH_PROGS($1, $2, , $3)])
  if test "x[$]$1" = x; then
    AC_MSG_NOTICE([Required tool $2 not found in PATH, checking built-in])
    if type -p $2 > /dev/null 2>&1; then
      AC_MSG_NOTICE([Found $2 as shell built-in. Using it])
      $1="$2"
    else
      AC_MSG_ERROR([Required tool $2 also not found as built-in.])
    fi
  fi
  UTIL_CHECK_NONEMPTY($1)
])