autoconf/libm4.m4

divert(-1)                                                   -*- Autoconf -*-
# This file is part of Autoconf.
# Base m4 layer.
# Requires GNU m4.
# Copyright (C) 1999 Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program 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 for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
#
# As a special exception, the Free Software Foundation gives unlimited
# permission to copy, distribute and modify the configure scripts that
# are the output of Autoconf.  You need not follow the terms of the GNU
# General Public License when using or distributing such scripts, even
# though portions of the text of Autoconf appear in them.  The GNU
# General Public License (GPL) does govern all other use of the material
# that constitutes the Autoconf program.
#
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# (in certain cases, depending on the input) into the output of
# Autoconf.  We call these the "data" portions.  The rest of the Autoconf
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# of the data portions to output in any given case.  We call these
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# such potential, you must delete any notice of this special exception
# to the GPL from your modified version.
#
# Written by Akim Demaille.
#

changequote([, ])

# Some old m4's don't support m4exit.  But they provide
# equivalent functionality by core dumping because of the
# long macros we define.
ifdef([__gnu__], ,
[errprint(Autoconf requires GNU m4. Install it before installing Autoconf or
set the M4 environment variable to its path name.)
m4exit(2)])



## --------------------------------- ##
## Defining macros and name spaces.  ##
## --------------------------------- ##

# Name spaces.

# Sometimes we want to disable some *set* of macros, and restore them
# later.  We provide support for this via name spaces.

# There are basically three characters playing this scene: defining a
# macro in a namespace, disabling a namespace, and restoring a namespace
# (i.e., all the definitions it holds).

# Technically, to define a MACRO in NAMESPACE means to define the
# macro named `NAMESPACE::MACRO' to the VALUE.  At the same time, we
# append `undefine(NAME)' in the macro named `m4_disable(NAMESPACE)',
# and similarly a binding of NAME to the value of `NAMESPACE::MACRO'
# in `m4_enable(NAMESPACE)'.  These mechanisms allow to bind the
# macro of NAMESPACE and to unbind them at will.

# Of course this implementation is not really efficient: m4 has to
# grow strings which can become quickly huge, which slows it
# significantly.  A better implementation should be a list of the
# symbols associated to the name space, and m4_enable?m4_disable
# would just loop over this list.  Unfortunately loops of active
# symbols are extremely delicate in m4, and I'm still unsure of the
# implementation I want.  So, until we reach a perfect agreement on
# foreach loops implementation, I prefer to use the brute force.

# It should be noted that one should avoid as much as possible to use
# `define' for temporaries.  Now that `define' as quite a complex
# meaning, it is an expensive operations that should be limited to
# macros.  Use `m4_define' for temporaries.

# Private copies of the macros we used in entering / exiting the
# libm4 name space.  It is much more convenient than fighting with
# the renamed version of define etc.

define([m4_changequote], defn([changequote]))
define([m4_define],      defn([define]))
define([m4_defn],        defn([defn]))
define([m4_dnl],         defn([dnl]))
define([m4_indir],       defn([indir]))
define([m4_popdef],      defn([popdef]))
define([m4_pushdef],     defn([pushdef]))
define([m4_undefine],    defn([undefine]))


m4_define([m4_namespace_push], [m4_pushdef([m4_namespace], [$1])])
m4_define([m4_namespace_pop],  [m4_popdef([m4_namespace])])

m4_namespace_push([libm4])



# m4_namespace_register(NAMESPACE, NAME)
# --------------------------------------
#
# Register NAME in NAMESPACE, i.e., append the binding/unbinding in
# `m4_disable(NAMESPACE)'/`m4_enable(NAMESPACE)'.
m4_define([m4_namespace_register],
[m4_define([m4_disable($1)],
           m4_defn([m4_disable($1)])[m4_undefine([$2])])dnl
m4_define([m4_enable($1)],
           m4_defn([m4_enable($1)])[m4_define([$2], m4_defn([$1::$2]))])dnl
])


# m4_namespace_define(NAMESPACE, NAME, VALUE)
# -------------------------------------------
#
# Assign VALUE to NAME in NAMESPACE, and register it.
m4_define([m4_namespace_define],
[m4_define([$1::$2], [$3])dnl
m4_namespace_register([$1], [$2])dnl
])


# define(NAME, VALUE)
# -------------------
#
# Assign VALUE to NAME in the current name space, and bind it at top level.
m4_define([define],
[m4_namespace_define(m4_namespace, [$1], [$2])dnl
m4_define([$1], [$2])dnl
])

# Register define too.
m4_namespace_define(libm4, [define], defn([define]))


# Put the m4 builtins into the `libm4' name space.  We cannot use `define'
# here because of the very special handling of `defn' for builtins.

# The following macro is useless but here, so undefine once done.
m4_define(m4_namespace_builtin,
[m4_define([libm4::$1], defn([$1]))
m4_namespace_register(libm4, [$1])])

m4_namespace_builtin([builtin])
m4_namespace_builtin([changequote])
m4_namespace_builtin([defn])
m4_namespace_builtin([dnl])
m4_namespace_builtin([esyscmd])
m4_namespace_builtin([ifdef])
m4_namespace_builtin([ifelse])
m4_namespace_builtin([indir])
m4_namespace_builtin([patsubst])
m4_namespace_builtin([popdef])
m4_namespace_builtin([pushdef])
m4_namespace_builtin([regexp])
m4_namespace_builtin([undefine])
m4_namespace_builtin([syscmd])
m4_namespace_builtin([sysval])

m4_undefine([m4_namespace_builtin])


# m4_disable(NAMESPACE)
# ---------------------
#
# Undefine all the macros of NAMESPACE.
m4_define([m4_disable], [m4_indir([m4_disable($1)])])


# m4_enable(NAMESPACE)
# --------------------
#
# Restore all the macros of NAMESPACE.
m4_define([m4_enable], [m4_indir([m4_enable($1)])])


# m4_rename(SRC, DST)
# -------------------
#
# Rename the macro SRC as DST.
define([m4_rename],
[m4_define([$2], m4_defn([$1]))m4_undefine([$1])])

# Some m4 internals have names colliding with tokens we might use.
# Rename them a` la `m4 --prefix-builtins'.
m4_rename([eval],   [m4_eval])
m4_rename([shift],  [m4_shift])
m4_rename([format], [m4_format])


## --------------------------------------------- ##
## Move some m4 builtins to a safer name space.  ##
## --------------------------------------------- ##

# m4_errprint(MSG)
# ----------------
# Same as `errprint', but reports the file and line.
define(m4_errprint, [errprint(__file__:__line__: [$1
])])


# m4_warn(MSG)
# ------------
# Warn the user.
define(m4_warn, [m4_errprint([warning: $1])])


# m4_fatal(MSG, [EXIT-STATUS])
# ----------------------------
# Fatal the user.                                                      :)
define(m4_fatal,
[m4_errprint([error: $1])dnl
m4exit(ifelse([$2],, 1, [$2]))])



# We also want to neutralize include (and sinclude for symmetry),
# but we want to extend them slightly: warn when a file is included
# several times.  This is in general a dangerous operation because
# quite nobody quotes the first argument of define.
#
# For instance in the following case:
#   define(foo, [bar])
# then a second reading will turn into
#   define(bar, [bar])
# which is certainly not what was meant.

# m4_include_unique(FILE)
# -----------------------
# Declare that the FILE was loading; and warn if it has already
# been included.
define(m4_include_unique,
[ifdef([m4_include($1)],
       [m4_warn([file `$1' included several times])])dnl
define([m4_include($1)])])


# m4_include(FILE)
# ----------------
# As the builtin include, but warns against multiple inclusions.
define(m4_include,
[m4_include_unique([$1])dnl
builtin([include], [$1])])


# m4_sinclude(FILE)
# -----------------
# As the builtin sinclude, but warns against multiple inclusions.
define(m4_sinclude,
[m4_include_unique([$1])dnl
builtin([sinclude], [$1])])

# Neutralize include and sinclude.
undefine([include])
undefine([sinclude])


## --------------------------------------- ##
## Some additional m4 structural control.  ##
## --------------------------------------- ##

# Both `ifval' and `ifset' tests against the empty string.  The
# difference is that `ifset' is specialized on macros.
#
# In case of arguments of macros, eg $[1], it makes little difference.
# In the case of a macro `FOO', you don't want to check `ifval(FOO,
# TRUE)', because if `FOO' expands with commas, there is a shifting of
# the arguments.  So you want to run `ifval([FOO])', but then you just
# compare the *string* `FOO' against `', which, of course fails.
#
# So you want a variation of `ifset' that expects a macro name as $[1].
# If this macro is both defined and defined to a non empty value, then
# it runs TRUE etc.


# ifval(COND, IF-TRUE[, IF-FALSE])
# --------------------------------
# If COND is not the empty string, expand IF-TRUE, otherwise IF-FALSE.
# Comparable to ifdef.
define([ifval], [ifelse([$1],[],[$3],[$2])])


# ifset(MACRO, IF-TRUE[, IF-FALSE])
# --------------------------------
# If MACRO has no definition, or of its definition is the empty string,
# expand IF-FALSE, otherwise IF-TRUE.
define([ifset],
[ifdef([$1],
       [ifelse(defn([$1]), [], [$3], [$2])],
       [$3])])


# m4_default(EXP1, EXP2)
# ----------------------
# Returns EXP1 if non empty, otherwise EXP2.
define([m4_default], [ifval([$1], [$1], [$2])])


# m4_case(SWITCH, VAL1, IF-VAL1, VAL2, IF-VAL2, ..., DEFAULT)
# -----------------------------------------------------------
# m4 equivalent of
# switch (SWITCH)
# {
#   case VAL1:
#     IF-VAL1;
#     break;
#   case VAL2:
#     IF-VAL2;
#     break;
#   ...
#   default:
#     DEFAULT;
#     break;
# }.
# All the values are optional, and the macro is robust to active
# symbols properly quoted.
define(m4_case,
[ifelse([$#], 0, [],
	[$#], 1, [],
	[$#], 2, [$2],
        [$1], [$2], [$3],
        [m4_case([$1], m4_shift(m4_shift(m4_shift($@))))])])


# m4_match(SWITCH, RE1, VAL1, RE2, VAL2, ..., DEFAULT)
# ----------------------------------------------------
# m4 equivalent of
#
# if (SWITCH =~ RE1)
#   VAL1;
# elif (SWITCH =~ RE2)
#   VAL2;
# elif ...
#   ...
# else
#   DEFAULT
#
# All the values are optional, and the macro is robust to active symbols
# properly quoted.
define(m4_match,
[ifelse([$#], 0, [],
	[$#], 1, [],
	[$#], 2, [$2],
        regexp([$1], [$2]), -1, [m4_match([$1],
                                          m4_shift(m4_shift(m4_shift($@))))],
        [$3])])


## --------------------- ##
## Implementing m4 loops ##
## --------------------- ##


# m4_for(VARIABLE, FROM, TO, EXPRESSION)
# --------------------------------------
# Expand EXPRESSION defining VARIABLE to FROM, FROM + 1, ..., TO.
# Both limits are included.
define([m4_for],
[pushdef([$1], [$2])_m4_for([$1], [$2], [$3], [$4])popdef([$1])])

# Low level macros used to define m4_for.
# Use m4_define for temporaries.
define([_m4_for],
[$4[]ifelse($1, [$3], [],
            [m4_define([$1], incr($1))_m4_for([$1], [$2], [$3], [$4])])])



# Implementing `foreach' loops in m4 is much more tricky than it may
# seem.  Actually, the example of a `foreach' loop in the m4
# documentation is wrong: it does not quote the arguments properly,
# which leads to undesired expansions.
#
# The example in the documentation is:
#
# | # foreach(x, (item_1, item_2, ..., item_n), stmt)
# | define(`foreach',
# |        `pushdef(`$1', `')_foreach(`$1', `$2', `$3')popdef(`$1')')
# | define(`_arg1', `$1')
# | define(`_foreach',
# | 	  `ifelse(`$2', `()', ,
# | 		  `define(`$1', _arg1$2)$3`'_foreach(`$1', (shift$2), `$3')')')
#
# But then if you run
#
# | define(a, 1)
# | define(b, 2)
# | define(c, 3)
# | foreach(`f', `(`a', `(b', `c)')', `echo f
# | ')
#
# it gives
#
#  => echo 1
#  => echo (2,3)
#
# which is not what is expected.
#
# Once you understood this, you turn yourself into a quoting wizard,
# and come up with the following solution:
#
# | # foreach(x, (item_1, item_2, ..., item_n), stmt)
# | define(`foreach', `pushdef(`$1', `')_foreach($@)popdef(`$1')')
# | define(`_arg1', ``$1'')
# | define(`_foreach',
# |  `ifelse($2, `()', ,
# | 	     `define(`$1', `_arg1$2')$3`'_foreach(`$1', `(shift$2)', `$3')')')
#
# which this time answers
#
#  => echo a
#  => echo (b
#  => echo c)
#
# Bingo!


# m4_foreach(VARIABLE, LIST, EXPRESSION)
# --------------------------------------
# Expand EXPRESSION assigning to VARIABLE each value of the LIST
# (LIST should have the form `[(item_1, item_2, ..., item_n)]'),
# i.e. the whole list should be *quoted*.  Quote members too if
# you don't want them to be expanded.
#
# This macro is robust to active symbols:
#    define(active, ACTIVE)
#    m4_foreach([Var], [([active], [b], [active])], [-Var-])end
#    => -active--b--active-end
define(m4_foreach,
[pushdef([$1], [])_m4_foreach($@)popdef([$1])])

# Low level macros used to define m4_foreach.
# Use m4_define for temporaries.
define(m4_car, [[$1]])
define(_m4_foreach,
[ifelse($2, [()], ,
        [m4_define([$1], [m4_car$2])$3[]_m4_foreach([$1],
                                                    [(m4_shift$2)],
                                                    [$3])])])


## ----------------------- ##
## Text processing in m4.  ##
## ----------------------- ##

# m4_quote(STRING)
# ----------------
# Return STRING quoted.
#
# It is important to realize the difference between `quote(exp)' and
# `[exp]': in the first case you obtain the quoted *result* of the
# expansion of EXP, while in the latter you just obtain the string
# `exp'.
define([m4_quote], [[$@]])


# m4_split(STRING, [REGEXP])
# --------------------------
#
# Split STRING into an m4 list of quoted elements.  The elements are
# quoted with [ and ].  Beginning spaces and end spaces *are kept*.
# Use m4_strip to remove them.
#
# REGEXP specifies where to split.  Default is [\t ]+.
#
# Pay attention to the changequotes.  Inner changequotes exist for
# obvious reasons (we want to insert square brackets).  Outer
# changequotes are needed because otherwise the m4 parser, when it
# sees the closing bracket we add to the result, believes it is the
# end of the body of the macro we define.  And since the active quote
# when `define' is called are not the ones which were used in its
# definition, we cannot use `define' as defined above.  Therefore,
# using m4's builtin `m4_define', which is indepedent from the
# current quotes, to define `m4_split', and then register `m4_split'
# in libm4.
#
# Also, notice that $1 is quoted twice, since we want the result to
# be quoted.  Then you should understand that the argument of
# patsubst is ``STRING'' (i.e., with additional `` and '').
#
# This macro is safe on active symbols, i.e.:
#   define(active, ACTIVE)
#   m4_split([active active ])end
#   => [active], [active], []end

changequote(<<, >>)
m4_define(m4_split,
<<changequote(``, '')dnl
[dnl Can't use m4_default here instead of ifelse, because m4_default uses
dnl [ and ] as quotes.
patsubst(````$1'''',
	  ifelse(``$2'',, ``[   ]+'', ``$2''),
	  ``], ['')]dnl
changequote([, ])>>)
changequote([, ])
changequote(<<, >>)

m4_namespace_register(m4_split, [libm4])



# m4_join(STRING)
# ---------------
# If STRING contains end of lines, replace them with spaces.  If there
# are backslashed end of lines, remove them.  This macro is safe with
# active symbols.
#    define(active, ACTIVE)
#    m4_join([active
#    act\
#    ive])end
#    => active activeend
define([m4_join],
[translit(patsubst([[[$1]]], [\\
]), [
], [ ])])


# m4_strip(STRING)
# ----------------
# Expands into STRING with tabs and spaces singled out into a single
# space, and removing leading and trailing spaces.
#
# This macro is robust to active symbols.
#    define(active, ACTIVE)
#    m4_strip([  active  		active ])end
#    => active activeend
#
# This macro is fun!  Because we want to preserve active symbols, STRING
# must be quoted for each evaluation, which explains there are 4 levels
# of brackets around $1 (don't forget that the result must be quoted
# too, hence one more quoting than applications).
#
# Then notice the patsubst of the middle: it is in charge of removing
# the leading space.  Why not just `patsubst(..., [^ ])'?  Because this
# macro will receive the output of the preceding patsubst, i.e. more or
# less [[STRING]].  So if there is a leading space in STRING, then it is
# the *third* character, since there are two leading `['; Equally for
# the outer patsubst.
define([m4_strip],
[patsubst(patsubst(patsubst([[[[$1]]]],
                            [[ 	]+], [ ]),
                   [^\(..\) ], [\1]),
          [ \(.\)$], [\1])])



# m4_append(MACRO-NAME, STRING)
# -----------------------------
# Redefine MACRO-NAME to hold its former content plus STRING at the
# end.  It is valid to use this macro with MACRO-NAME undefined.
#
# This macro is robust to active symbols.  It can be used to grow
# strings.
#
#    | define(active, ACTIVE)
#    | m4_append([sentence], [This is an])
#    | m4_append([sentence], [ active ])
#    | m4_append([sentence], [symbol.])
#    | sentence
#    | undefine([active])dnl
#    | sentence
#    => This is an ACTIVE symbol.
#    => This is an active symbol.
#
# It can be used to define hooks.
#
#    | define(active, ACTIVE)
#    | m4_append([hooks], [define([act1], [act2])])
#    | m4_append([hooks], [define([act2], [active])])
#    | undefine([active])
#    | act1
#    | hooks
#    | act1
#    => act1
#    =>
#    => active
define(m4_append,
[define([$1],
ifdef([$1], [defn([$1])])[$2])])


# m4_list_append(MACRO-NAME, STRING)
# ----------------------------------
# Same as `m4_append', but each element is separated by `, '.
define(m4_list_append,
[define([$1],
ifdef([$1], [defn([$1]), ])[$2])])




## ----------------------------------- ##
## Helping macros to display strings.  ##
## ----------------------------------- ##


# m4_wrap(STRING, [PREFIX], [FIRST-PREFIX], [WIDTH])
# --------------------------------------------------
# Expands into STRING wrapped to hold in WIDTH columns (default = 79).
# If prefix is set, each line is prefixed with it.  If FIRST-PREFIX is
# specified, then the first line is prefixed with it.  As a special
# case, if the length of the first prefix is greater than that of
# PREFIX, then FIRST-PREFIX will be left alone on the first line.
#
# Typical outputs are:
#
# m4_wrap([Short string */], [   ], [/* ], 20)
#  => /* Short string */
#
# m4_wrap([Much longer string */], [   ], [/* ], 20)
#  => /* Much longer
#  =>    string */
#
# m4_wrap([Short doc.], [          ], [  --short ], 30)
#  =>   --short Short doc.
#
# m4_wrap([Short doc.], [          ], [  --too-wide ], 30)
#  =>   --too-wide
#  =>           Short doc.
#
# m4_wrap([Super long documentation.], [          ], [  --too-wide ], 30)
#  =>   --too-wide
#  => 	  Super long
#  => 	  documentation.
#
# FIXME: there is no checking of a longer PREFIX than WIDTH, but do
# we really want to bother with people trying each single corner
# of a software?
#
# This macro does not leave a trailing space behind the last word,
# what complicates it a bit.  The algorithm is stupid simple: all the
# words are preceded by m4_Separator which is defined to empty for the
# first word, and then ` ' (single space) for all the others.
define([m4_wrap],
[pushdef([m4_Prefix], m4_default([$2], []))dnl
pushdef([m4_Prefix1], m4_default([$3], [m4_Prefix]))dnl
pushdef([m4_Width], m4_default([$4], 79))dnl
pushdef([m4_Cursor], len(m4_Prefix1))dnl
pushdef([m4_Separator], [])dnl
m4_Prefix1[]dnl
ifelse(m4_eval(m4_Cursor > len(m4_Prefix)),
       1, [define([m4_Cursor], len(m4_Prefix))
m4_Prefix])[]dnl
m4_foreach([m4_Word], (m4_split(m4_strip(m4_join([$1])))),
[m4_define([m4_Cursor], m4_eval(m4_Cursor + len(m4_Word) + 1))dnl
dnl New line if too long, else insert a space unless it is the first
dnl of the words.
ifelse(m4_eval(m4_Cursor > m4_Width),
       1, [define([m4_Cursor], m4_eval(len(m4_Prefix) + len(m4_Word) + 1))]
m4_Prefix,
       [m4_Separator])[]dnl
m4_Word[]dnl
m4_define([m4_Separator], [ ])])dnl
popdef([m4_Separator])dnl
popdef([m4_Cursor])dnl
popdef([m4_Width])dnl
popdef([m4_Prefix1])dnl
popdef([m4_Prefix])dnl
])