not-autoshell.m4

dnl  **************************************************************************
dnl         _   _       _      ___        _        _              _     
dnl        | \ | |     | |    / _ \      | |      | |            | |    
dnl        |  \| | ___ | |_  / /_\ \_   _| |_ ___ | |_ ___   ___ | |___ 
dnl        | . ` |/ _ \| __| |  _  | | | | __/ _ \| __/ _ \ / _ \| / __|
dnl        | |\  | (_) | |_  | | | | |_| | || (_) | || (_) | (_) | \__ \
dnl        \_| \_/\___/ \__| \_| |_/\__,_|\__\___/ \__\___/ \___/|_|___/
dnl
dnl              A collection of useful m4 macros for GNU Autotools
dnl
dnl                                               -- Released under GNU GPL3 --
dnl
dnl                                  https://github.com/madmurphy/not-autotools
dnl  **************************************************************************



dnl  **************************************************************************
dnl  S H E L L - A G N O S T I C   M 4   A B S T R A C T I O N S
dnl  **************************************************************************



dnl  NS_SETVARS(var1[, val1][, var2[, val2][, ... varN[, valN]]])
dnl  **************************************************************************
dnl
dnl  M4 sugar to set the value of many shell variables altogether
dnl
dnl  Same as `var1=val1 var2=val2 ... varN=valN`.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_SETVARS],
	[m4_if([$#], [0], [],
		[AS_VAR_SET([$1], [$2])[]m4_if([$#], [1], [], [$#], [2], [],
			[m4_newline()NS_SETVARS(m4_shift2($@))])])])


dnl  NS_GETVAR(var)
dnl  **************************************************************************
dnl
dnl  M4 sugar to get the value of a shell variable
dnl
dnl  Same as `$var`.
dnl
dnl  Example:
dnl
dnl      NS_SETVARS([MY_MESSAGE], ['This is a test'])
dnl      AC_MSG_NOTICE([My message --> NS_GETVAR([MY_MESSAGE])])
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.1.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_GETVAR],
	[AS_LITERAL_WORD_IF([$1], [${$1}], [$(eval echo "\${$1}")])])


dnl  NS_GETOUT(command)
dnl  **************************************************************************
dnl
dnl  M4 sugar to get the output of a command
dnl
dnl  Same as `$(command)`. This macro works exactly like `m4_esyscmd()`, but
dnl  instead of executing a command during the `autoreconf` process, it
dnl  executes it during the `configure` process, when all M4 macros have been
dnl  already expanded. The returned value cannot therefore be stored in another
dnl  macro, but must be stored in a shell variable.
dnl
dnl  Example:
dnl
dnl      AC_MSG_NOTICE([Today is NS_GETOUT([date])])
dnl      AC_MSG_NOTICE([NS_GETOUT([echo 'This is a test'])])
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_GETOUT], [@S|@@{:@$1@:}@])


dnl  NS_UNSET(var1[, var2[, var3[, ... varN]]])
dnl  **************************************************************************
dnl
dnl  Like `AS_UNSET()`, but allows to unset many variables altogether
dnl
dnl  For example:
dnl
dnl      NS_SETVARS([FIRST_VAR], ['first value'],
dnl          [SECOND_VAR], ['second value'],
dnl          [THIRD_VAR], ['third value'])
dnl
dnl      NS_UNSET([FIRST_VAR], [SECOND_VAR], [THIRD_VAR])
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_UNSET],
	[m4_if([$#], [0], [],
		[AS_UNSET(m4_normalize([$1]))])[]m4_if([$#], [1], [],
			[m4_newline()[]NS_UNSET(m4_shift($@))])])


dnl  NS_MOVEVAR(destination, source)
dnl  **************************************************************************
dnl
dnl  Copies the value of `source` into the shell variable `destination`, then
dnl  unsets `source` if this is set
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_MOVEVAR],
	[AS_VAR_COPY([$1], [$2])[]m4_newline()[]AS_UNSET([$2])])


dnl  NS_REPLACEVAR(destination, source)
dnl  **************************************************************************
dnl
dnl  If `source` is set, copies the value of `source` into the shell variable
dnl  `destination` then unsets `source`; if `source` is not set but
dnl  `destination` is set, unsets `destination`
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.1.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_REPLACEVAR],
	[AS_VAR_SET_IF([$2],
		[AS_VAR_COPY([$1], [$2])[]m4_newline()[]AS_UNSET([$2])],
		[AS_UNSET([$1])])])


dnl  NS_IF(test1, run1[, test2, run2[, testN, runN]][, run-if-false])
dnl  **************************************************************************
dnl
dnl  Shell `if` / `else`
dnl
dnl  This macro is a clone of `AS_IF()` written with the main purpose of being
dnl  safely used by the `NS_PP_IF()` macro families. It has been designed as M4
dnl  sugar to be used internally by the **Not Autotools** project, but can be
dnl  safely invoked by the final user. Usage is identical to `AS_IF()`.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_IF],
[m4_if([$#], [0], [],
[$#], [1], [],
[$#], [2], [if [$1]
then :
	$2
fi],
[$#], [3],
[if [$1]
then :
	$2[]m4_ifnblank([$3], [
else :
	$3])
fi],
[if [$1]
then :
	$2
el[]NS_IF(m4_shift2($@))])])


dnl  NS_PP_IF(macro, test1, run1[, test2, run2[, testN, runN]][, run-if-false])
dnl  **************************************************************************
dnl
dnl  Shell `if` / `else`, preprocessing each `runN` argument with `macro`
dnl
dnl  Example:
dnl
dnl      AS_VAR_SET([TESTNUM], [31])
dnl
dnl      NS_PP_IF([AC_MSG_NOTICE],
dnl          [test "${TESTNUM}" -eq 44],
dnl              [Number is 44],
dnl          [test "${TESTNUM}" -eq 31],
dnl              [Number is 31],
dnl              [Invalid number])
dnl
dnl  Prints:
dnl
dnl      configure: Number is 31
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: `NS_IF()`
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_PP_IF],
	[NS_IF(m4_shift(m4_for([__argn__], [3], m4_eval([(($# + 1) >> 1) << 1]),
		[2], [, m4_argn(m4_decr(__argn__), $@), $1(m4_argn(__argn__,
		$@))])[])[]m4_if(m4_eval([($# >> 1) << 1]), [$#],
		[, $1(m4_argn($#, $@))]))])


dnl  NS_STDOUT([text])
dnl  **************************************************************************
dnl
dnl  A version of `AS_ECHO()` guaranteed to output immediatelly to the Standard
dnl  Output
dnl
dnl  As in `AS_ECHO()` the `text` argument is passed verbatim, without shell
dnl  quoting. For a version that treats the `text` argument in the same way as
dnl  `AC_MSG_NOTICE()` does, please see `NS_STDOUT_UNQUOTED()`.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_STDOUT],
	[echo $1])


dnl  NS_STDOUT_UNQUOTED([text])
dnl  **************************************************************************
dnl
dnl  A version of `AS_ECHO()` guaranteed to output immediatelly to the Standard
dnl  Output, with backquote expansion protection
dnl
dnl  This is a quote-safe version of `NS_STDOUT()`. The `text` argument does
dnl  not need shell quotes, which will be escaped if found.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_STDOUT_UNQUOTED],
	[echo "_AS_QUOTE([$1])"])


dnl  NS_STRING_IF(test1, str1[, test2, str2[, testN, strN]][, string-if-false])
dnl  **************************************************************************
dnl
dnl  A ternary-operator-like macro for shell strings
dnl
dnl  Example:
dnl
dnl      AS_VAR_SET([TESTNUM], ['31'])
dnl
dnl      AS_VAR_SET([NUMSTATUS],
dnl          NS_STRING_IF([test "${TESTNUM}" -eq 44],
dnl                  ['valid'],
dnl              [test "${TESTNUM}" -eq 31],
dnl                  ['mostly valid'],
dnl                  ["invalid (${TESTNUM})"]))
dnl
dnl      AC_MSG_NOTICE([Status is "${NUMSTATUS}"])
dnl
dnl  Prints:
dnl
dnl      configure: Status is "mostly valid"
dnl
dnl  The `strN` arguments are passed verbatim, without shell quoting. For a
dnl  version that treats the `strN` arguments in the same way as
dnl  `AC_MSG_NOTICE()` does, please see `NS_STRING_IF_UNQUOTED()`.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: `NS_PP_IF()` and `NS_STDOUT()`
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_STRING_IF],
	["@S|@@{:@{ NS_PP_IF([NS_STDOUT], $@) }@:}@"])


dnl  NS_STRING_IF_UNQUOTED(test1, str1[, testN, strN][, string-if-false])
dnl  **************************************************************************
dnl
dnl  A ternary-operator-like macro for shell strings, with backquote expansion
dnl  protection
dnl
dnl  This is a quote-safe version of `NS_STRING_IF()`. The `strN` arguments do
dnl  not need shell quotes, which will be escaped if found.
dnl
dnl  Example:
dnl
dnl      AS_VAR_SET([NUMSTATUS],
dnl          NS_STRING_IF_UNQUOTED([test "${TESTNUM}" -eq 44],
dnl                  [valid],
dnl              [test "${TESTNUM}" -eq 31],
dnl                  [mostly valid],
dnl                  [invalid (${TESTNUM})]))
dnl
dnl      AC_MSG_NOTICE([Status is "${NUMSTATUS}"])
dnl
dnl  Prints:
dnl
dnl      configure: Status is "mostly valid"
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: `NS_PP_IF()` and `NS_STDOUT_UNQUOTED()`
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_STRING_IF_UNQUOTED],
	["@S|@@{:@{ NS_PP_IF([NS_STDOUT_UNQUOTED], $@) }@:}@"])


dnl  NS_FOR(initialization, statement)
dnl  **************************************************************************
dnl
dnl  M4 sugar to create a "for" shell loop
dnl
dnl  For example:
dnl
dnl      # Iterate over all `configure` arguments and check if `--docdir` has
dnl      # been given
dnl      NS_FOR([_this_arg_],
dnl          [AS_CASE([${_this_arg_}], [--docdir=*], [
dnl              AS_VAR_SET([is_auto_docdir], [no])
dnl              NS_BREAK
dnl          ])])
dnl
dnl      AS_IF([test "x${is_auto_docdir}" != xno],
dnl          [AC_MSG_NOTICE([Using default value for <docdir>])],
dnl          [AC_MSG_NOTICE([Using user-given value for <docdir>])])
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_FOR],
	[{ for $1; do[]m4_newline()$2[]m4_newline()done }])


dnl  NS_WHILE(initialization, statement)
dnl  **************************************************************************
dnl
dnl  M4 sugar to create a "while" shell loop
dnl
dnl  See `NS_FOR()` for an example -- the syntax is identical.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_WHILE],
	[{ while $1; do[]m4_newline()$2[]m4_newline()done }])


dnl  NS_UNTIL(initialization, statement)
dnl  **************************************************************************
dnl
dnl  M4 sugar to create an "until" shell loop
dnl
dnl  See `NS_FOR()` for an example -- the syntax is identical.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_UNTIL],
	[{ until $1; do[]m4_newline()$2[]m4_newline()done }])


dnl  NS_BREAK()
dnl  **************************************************************************
dnl
dnl  M4 sugar that expands to a shell "break" command, to be used within loops
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
AC_DEFUN([NS_BREAK],
	[m4_newline()break;m4_newline()])


dnl  NS_CONTINUE()
dnl  **************************************************************************
dnl
dnl  M4 sugar that expands to a shell "continue" command, to be used within
dnl  loops
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
AC_DEFUN([NS_CONTINUE],
	[m4_newline()continue;m4_newline()])


dnl  NS_TEST_EQ(left1, right1[, left2, right2[, ... leftN, rightN]])
dnl  **************************************************************************
dnl
dnl  Checks if all equality tests have succeeded and triggers `true` or `false`
dnl  accordingly
dnl
dnl  For example,
dnl
dnl      AS_VAR_SET([first], [yes])
dnl      AS_VAR_SET([second], [no])
dnl
dnl      AS_IF([NS_TEST_EQ(
dnl              [${first}], [yes],
dnl              [${second}], [no])],
dnl          [AC_MSG_NOTICE([Test passed])],
dnl          [AC_MSG_NOTICE([Test not passed])])
dnl
dnl  will print
dnl
dnl      Test passed
dnl
dnl  To understand how the macro works, the following code
dnl
dnl      NS_TEST_EQ([one], [two], [three], [four])
dnl
dnl  expands to
dnl
dnl      test "?one?three" = "?two?four"
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEST_EQ],
	[m4_if([$#], [0], [:], [$#], [1], [:], [$#], [2],
		[test "_AS_QUOTE([[?$1]])" != "_AS_QUOTE([[?$2]])"],
		[NS_TEST_EQ([$1?$3], [$2?$4]m4_if([$#], [3], [], [$#], [4], [],
			[, m4_shift3(m4_shift($@))]))])])


dnl  NS_TEST_NE(left1, right1[, left2, right2[, ... leftN, rightN]])
dnl  **************************************************************************
dnl
dnl  Checks if at least one equality test has failed and triggers `true` or
dnl  `false` accordingly
dnl
dnl  For example,
dnl
dnl      AS_VAR_SET([first], [yes])
dnl      AS_VAR_SET([second], [no])
dnl
dnl      AS_IF([NS_TEST_NE(
dnl              [${first}], [yes],
dnl              [${second}], [no])],
dnl          [AC_MSG_NOTICE([Test passed])],
dnl          [AC_MSG_NOTICE([Test not passed])])
dnl
dnl  will print
dnl
dnl      Test not passed
dnl
dnl  All arguments do not need shell quotes, which will be escaped if found.
dnl
dnl  To understand how the macro works, the following code
dnl
dnl      NS_TEST_NE([one], [two], [three], [four])
dnl
dnl  expands to
dnl
dnl      test "?one?three" != "?two?four"
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEST_NE],
	[m4_if([$#], [0], [:], [$#], [1], [:], [$#], [2],
		[test "_AS_QUOTE([[?$1]])" != "_AS_QUOTE([[?$2]])"],
		[NS_TEST_NE([$1?$3], [$2?$4]m4_if([$#], [3], [], [$#], [4], [],
			[, m4_shift3(m4_shift($@))]))])])


dnl  NS_TEST_AEQ(string1, string2[, string3[, ... stringN]])
dnl  **************************************************************************
dnl
dnl  Check if all arguments expand to the same string and triggers `true` or
dnl  `false` accordingly
dnl
dnl  For example,
dnl
dnl      AC_HEADER_STDBOOL
dnl
dnl      AC_CHECK_HEADERS([stddef.h stdint.h stdio.h stdlib.h])
dnl
dnl      AS_IF([NS_TEST_AEQ([yes],
dnl          [${ac_cv_header_stdio_h}], [${ac_cv_header_stddef_h}],
dnl          [${ac_cv_header_stdbool_h}], [${ac_cv_header_stdint_h}],
dnl          [${ac_cv_header_stdlib_h}])],
dnl              [AC_MSG_NOTICE([Test passed])],
dnl              [AC_MSG_ERROR([Test not passed])])
dnl
dnl  will likely print
dnl
dnl      Test passed
dnl
dnl  All arguments do not need shell quotes, which will be escaped if found.
dnl
dnl  To understand how the macro works, the following code
dnl
dnl      NS_TEST_AEQ([one], [two], [three], [four])
dnl
dnl  expands to
dnl
dnl      test "?two?three?four" != "?one?one?one"
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.2
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEST_AEQ],
	[m4_if([$#], [0], [:], [$#], [1], [:],
		[test "_AS_QUOTE(m4_dquote([?]m4_joinall([?], m4_shift($@))))" = "_AS_QUOTE(m4_dquote(m4_for([], [2], [$#], [1], [[?$1]])))"])])


dnl  NS_TEST_NAE(string1, string2[, string3[, ... stringN]])
dnl  **************************************************************************
dnl
dnl  Check if all arguments do **not** expand to the same string and triggers
dnl  `true` or `false` accordingly
dnl
dnl  For example,
dnl
dnl      AC_HEADER_STDBOOL
dnl
dnl      AC_CHECK_HEADERS([stddef.h stdint.h stdio.h stdlib.h])
dnl
dnl      AS_IF([NS_TEST_NAE([yes],
dnl          [${ac_cv_header_stdio_h}], [${ac_cv_header_stddef_h}],
dnl          [${ac_cv_header_stdbool_h}], [${ac_cv_header_stdint_h}],
dnl          [${ac_cv_header_stdlib_h}])],
dnl              [AC_MSG_ERROR([Test not passed])],
dnl              [AC_MSG_NOTICE([Test passed])])
dnl
dnl  will likely print
dnl
dnl      Test passed
dnl
dnl  All arguments do not need shell quotes, which will be escaped if found.
dnl
dnl  To understand how the macro works, the following code
dnl
dnl      NS_TEST_NAE([one], [two], [three], [four])
dnl
dnl  expands to
dnl
dnl      test "?two?three?four" != "?one?one?one"
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.2
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEST_NAE],
	[m4_if([$#], [0], [:], [$#], [1], [:],
		[test "_AS_QUOTE(m4_dquote([?]m4_joinall([?], m4_shift($@))))" != "_AS_QUOTE(m4_dquote(m4_for([], [2], [$#], [1], [[?$1]])))"])])


dnl  NS_TEXT_WRAP(text[, max-width=79])
dnl  **************************************************************************
dnl
dnl  M4 sugar to wrap a text into a fixed-width column
dnl
dnl  This macro is similar to the Unix `fmt` command, but it is implemented
dnl  using only `sed`. The `text` argument is passed verbatim, without shell
dnl  quoting. For a version that treats the `text` argument in the same way as
dnl  `AC_MSG_NOTICE()` does, please see `NS_TEXT_WRAP_UNQUOTED()`.
dnl
dnl  For example, the following code:
dnl
dnl      AS_VAR_SET([INCIPIT],
dnl          ['Lorem ipsum dolor sit amet, consectetur adipiscing elit.'])
dnl
dnl      NS_TEXT_WRAP(["${INCIPIT}"' Phasellus sit amet enim ac tellus aliquam
dnl      lacinia. Nullam iaculis imperdiet lorem, ac consectetur nisi vulputate
dnl      et. Proin a eros at orci pharetra fringilla non accumsan nulla. Fusce
dnl      sem dolor, facilisis ac vestibulum a, lacinia sed arcu.'], [40])
dnl
dnl  will generate the following shell output:
dnl
dnl      Lorem ipsum dolor sit amet, consectetur
dnl      adipiscing elit. Phasellus sit amet enim
dnl      ac tellus aliquam lacinia. Nullam
dnl      iaculis imperdiet lorem, ac consectetur
dnl      nisi vulputate et. Proin a eros at orci
dnl      pharetra fringilla non accumsan nulla.
dnl      Fusce sem dolor, facilisis ac vestibulum
dnl      a, lacinia sed arcu.
dnl
dnl  The shell code produced by this macro is safely contained within curly
dnl  brackets, so that its output can be easily captured or piped, as in the
dnl  following example,
dnl
dnl      AS_VAR_SET([FOO],
dnl          ["$(NS_TEXT_WRAP(['Hello world!'], [6]))"])
dnl
dnl      AS_ECHO("${FOO}")
dnl
dnl  which will print the following text:
dnl
dnl      Hello
dnl      world!
dnl
dnl  If `text` does not contain any shell expansions you should use
dnl  `AS_ECHO(['m4_text_wrap(m4_quote(m4_bpatsubst([TEXT GOES HERE], ['], ['\\''])),,, [MAX-WIDTH GOES HERE])'])`
dnl  instead of `NS_TEXT_WRAP()`, so that the `configure` script receives a
dnl  literal instead of a `sed` substitution to perform each time it is run.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.1
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEXT_WRAP], [{
	AC_REQUIRE([AC_PROG_SED])
	_newtxt_=$1
	while :; do
		_oldtxt_="${_newtxt_}"
		_newtxt_="$(echo -n "${_oldtxt_}" | ${SED} '
			s/^..\{'m4_default_nblank_quoted([$2], ['79'])'\}/&\x00/;
			s/^\(\S\+\)\x00\(\S*\)\s\|\(^\|\s\)\(\S*\)\x00/\1\2\x00\4/;
			s/^\x00//;
			s/\x00/\n/;
		')"
		test "x${_newtxt_}" != "x${_oldtxt_}" || break
	done
	echo "${_newtxt_}"
}])


dnl  NS_TEXT_WRAP_UNQUOTED(text[, max-width=79])
dnl  **************************************************************************
dnl
dnl  M4 sugar to wrap a text into a fixed-width column, with backquote
dnl  expansion protection
dnl
dnl  This is a quote-safe version of `NS_TEXT_WRAP()`. The `text` argument does
dnl  not need shell quotes, which will be escaped if found.
dnl
dnl  For example, the following code:
dnl
dnl      AS_VAR_SET([INCIPIT],
dnl          ['Lorem ipsum dolor sit amet, consectetur adipiscing elit.'])
dnl
dnl      NS_TEXT_WRAP_UNQUOTED([${INCIPIT} Phasellus sit amet enim ac tellus
dnl      aliquam lacinia. Nullam iaculis imperdiet lorem, ac consectetur nisi
dnl      vulputate et. Proin a eros at orci pharetra fringilla non accumsan
dnl      nulla. Fusce sem dolor, facilisis ac vestibulum a, lacinia sed arcu.],
dnl      [40])
dnl
dnl  will generate the following shell output:
dnl
dnl      Lorem ipsum dolor sit amet, consectetur
dnl      adipiscing elit. Phasellus sit amet enim
dnl      ac tellus aliquam lacinia. Nullam
dnl      iaculis imperdiet lorem,ac consectetur
dnl      nisi vulputate et. Proin a eros at orci
dnl      pharetra fringilla non accumsan nulla.
dnl      Fusce sem dolor,facilisis ac vestibulum
dnl      a,lacinia sed arcu.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: `NS_TEXT_WRAP()`
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEXT_WRAP_UNQUOTED],
	[m4_if([$#], [0],
		[NS_TEXT_WRAP],
		[NS_TEXT_WRAP(["]m4_dquote(_AS_QUOTE([[$1]]))["]m4_if([$#], [1], [], [, $2]))])])


dnl  NS_TEXT_WRAP_CENTER(text[, max-width=60[, screen-width=79]])
dnl  **************************************************************************
dnl
dnl  M4 sugar to wrap a text into a centered fixed-width column
dnl
dnl  This macro calls `NS_TEXT_WRAP()` and then centers each line. The `text`
dnl  argument is passed verbatim, without shell quoting.
dnl
dnl  For example, the following code:
dnl
dnl      AS_VAR_SET([INCIPIT],
dnl          ['Lorem ipsum dolor sit amet, consectetur adipiscing elit.'])
dnl
dnl      NS_TEXT_WRAP_CENTER(["${INCIPIT}"' Phasellus sit amet enim ac tellus
dnl      aliquam lacinia. Nullam iaculis imperdiet lorem, ac consectetur nisi
dnl      vulputate et. Proin a eros at orci pharetra fringilla non accumsan
dnl      nulla. Fusce sem dolor, facilisis ac vestibulum a, lacinia sed arcu.'],
dnl      [40], [70])
dnl
dnl  will generate the following shell output:
dnl
dnl                     Lorem ipsum dolor sit amet, consectetur
dnl                     adipiscing elit. Phasellus sit amet enim
dnl                        ac tellus aliquam lacinia. Nullam
dnl                     iaculis imperdiet lorem, ac consectetur
dnl                     nisi vulputate et. Proin a eros at orci
dnl                      pharetra fringilla non accumsan nulla.
dnl                     Fusce sem dolor, facilisis ac vestibulum
dnl                               a, lacinia sed arcu.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: `NS_TEXT_WRAP()`
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_TEXT_WRAP_CENTER],
	[{ NS_TEXT_WRAP([$1], m4_ifblank([$2], [['60']], [[$2]])) | while read _line_; do test "${@%:@_line_}" -ge m4_ifblank([$3], ['79'], [$3]) && echo "${_line_}" || echo "$(printf "%$(expr '(' m4_ifblank([$3], ['79'], [$3]) '-' "${@%:@_line_}" ')' '/' 2)s")${_line_}"
done; }])


dnl  NS_LITERAL_HEREDOC(content[, end-keyword])
dnl  **************************************************************************
dnl
dnl  M4 sugar to launch `cat << 'END_HEREDOC' ...`
dnl
dnl  Example
dnl
dnl      NS_LITERAL_HEREDOC([
dnl      Welcome to the build system of Foo package.
dnl
dnl      If you need help, please type ./configure --help
dnl      ])
dnl
dnl  By default, the end keyword chosen is `NS_END_HEREDOC`. You can use a
dnl  different keyword by using the optional `end-keyword` argument.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_LITERAL_HEREDOC],
	[{ cat << 'm4_default_nblank_quoted([$2], [NS_END_HEREDOC])'m4_newline()$1[]m4_newline()m4_default_nblank_quoted([$2], [NS_END_HEREDOC])[]m4_newline() }])


dnl  NS_HEREDOC(content[, end-keyword])
dnl  **************************************************************************
dnl
dnl  M4 sugar to launch `cat << END_HEREDOC ...`
dnl
dnl  Example
dnl
dnl      NS_HEREDOC([
dnl      Welcome to the build system of Foo package.
dnl      
dnl      If you need help, please type ${0} --help
dnl      ])
dnl
dnl  By default, the end keyword chosen is `NS_END_HEREDOC`. You can use a
dnl  different keyword by using the optional `end-keyword` argument.
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_HEREDOC],
	[{ cat << m4_default_nblank_quoted([$2], [NS_END_HEREDOC])[]m4_newline()$1[]m4_newline()m4_default_nblank_quoted([$2], [NS_END_HEREDOC])[]m4_newline() }])


dnl  NS_CATCH(shell-code[, stdout-var-name[, stderr-var-name]])
dnl  **************************************************************************
dnl
dnl  Execute custom shell code and save `stdout` and `stderr` into shell
dnl  variables
dnl
dnl  Both `stdout-var-name` and `stderr-var-name` can be left empty, and in
dnl  that case the respective file descriptor will be normally flushed.
dnl  Alternatively, they can be set to a hyphen (`-`), and in that case the
dnl  respective file descriptor will be redirected to `/dev/null`.
dnl
dnl  A few examples:
dnl
dnl      # Save both `stdout` and `stderr` into two variables
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [MY_STDOUT], [MY_STDERR])
dnl
dnl      # Save `stdout` into a variable and silence `stderr`
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [MY_STDOUT], [-])
dnl
dnl      # Save `stdout` into a variable and print `stderr` normally
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [MY_STDOUT])
dnl
dnl      # Save `stderr` into a variable and silence `stdout`
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [-], [MY_STDERR])
dnl
dnl      # Save `stderr` into a variable and print `stdout` normally
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [], [MY_STDERR])
dnl
dnl      # Silence both `stdout` and `stderr`
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [-], [-])
dnl
dnl      # Silence `stderr`, print only `stdout`
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [], [-])
dnl
dnl      # Silence `stdout`, print only `stderr`
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ], [-])
dnl
dnl      # Print both `stdout` and `stderr` normally
dnl      NS_CATCH([
dnl          echo 'This is stderr' 1>&2
dnl          echo 'This is stdout'
dnl      ])
dnl
dnl  This macro may be invoked before `AC_INIT()`.
dnl
dnl  NOTE:  `NS_CATCH()` incorporates an answer of mine on stackoverflow
dnl         (https://stackoverflow.com/a/59592881, "10. The POSIX-compliant
dnl         version #2").
dnl
dnl  Expansion type: shell code
dnl  Requires: nothing
dnl  Version: 1.0.0
dnl  Author: madmurphy
dnl
dnl  **************************************************************************
AC_DEFUN([NS_CATCH],
	[m4_if([$2$3], [],
			[{m4_newline()[]$1[]m4_newline()}],			
		[$2$3], [--],
			[{m4_newline(){m4_newline()[]$1[]m4_newline()} 1> /dev/null 2>&1[]m4_newline()}],
		[$2], [],
			[m4_if([$3], [-],
				[{m4_newline(){m4_newline()[]$1[]m4_newline()} 2> /dev/null[]m4_newline()}],
				[{m4_newline()[]AS_VAR_SET([$3], ["$({]m4_newline()[$1]m4_newline()[} 3>&2 2>&1 1>&3 3>&-)"])[]m4_newline()} 2>&1])],
		[$2], [-],
			[m4_if([$3], [],
				[{m4_newline(){m4_newline()[]$1[]m4_newline()} 1> /dev/null[]m4_newline()}],
				[{m4_newline()[]AS_VAR_SET([$3], ["$({]m4_newline()[$1]m4_newline()[} 3>&2 2>&1 1>&3 3>&-)"])[]m4_newline()} 2> /dev/null])],
		[$3], [],
			[AS_VAR_SET([$2], ["$({]m4_newline()[$1]m4_newline()[})"])],
		[$3], [-],
			[AS_VAR_SET([$2], ["$({]m4_newline()[$1]m4_newline()[} 2> /dev/null)"])],
			[# See https://stackoverflow.com/a/59592881
__sep__=$'\cZ'
{

	IFS=$'\n'"${__sep__}" read -r -d "${__sep__}" "$2";
	IFS=$'\n'"${__sep__}" read -r -d "${__sep__}" "$3";
	(IFS=$'\n'"${__sep__}" read -r -d "${__sep__}" __errno__; exit ${__errno__});
} <<__NA_EOF__
$((printf "${__sep__}%s${__sep__}%d${__sep__}" "$(((({ {m4_newline()[]$1[]m4_newline()}m4_newline()[]echo "${?}" 1>&3-; } | cut -z -d"${__sep__}" -f1 | tr -d '\0' 1>&4-) 4>&2- 2>&1- | cut -z -d"${__sep__}" -f1 | tr -d '\0' 1>&4-) 3>&1- | exit "$(cat)") 4>&1-)" "${?}" 1>&2) 2>&1)
__NA_EOF__
AS_UNSET([__sep__])
])])



dnl  **************************************************************************
dnl  NOTE:  The `NS_` prefix (which stands for "Not autoShell") is used with
dnl         the purpose of avoiding collisions with the default Autotools
dnl         prefixes `AC_`, `AM_`, `AS_`, `AX_`, `LT_`.
dnl  **************************************************************************



dnl  EOF