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1 # -*- Autoconf -*-
2 # This file is part of Autoconf.
3 # foreach-based replacements for recursive functions.
4 # Speeds up GNU M4 1.4.x by avoiding quadratic $@ recursion, but penalizes
5 # GNU M4 1.6 by requiring more memory and macro expansions.
6 #
7 # Copyright (C) 2008-2017 Free Software Foundation, Inc.
9 # This file is part of Autoconf. This program is free
10 # software; you can redistribute it and/or modify it under the
11 # terms of the GNU General Public License as published by the
12 # Free Software Foundation, either version 3 of the License, or
13 # (at your option) any later version.
14 #
15 # This program is distributed in the hope that it will be useful,
16 # but WITHOUT ANY WARRANTY; without even the implied warranty of
17 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 # GNU General Public License for more details.
19 #
20 # Under Section 7 of GPL version 3, you are granted additional
21 # permissions described in the Autoconf Configure Script Exception,
22 # version 3.0, as published by the Free Software Foundation.
23 #
24 # You should have received a copy of the GNU General Public License
25 # and a copy of the Autoconf Configure Script Exception along with
26 # this program; see the files COPYINGv3 and COPYING.EXCEPTION
27 # respectively. If not, see <https://www.gnu.org/licenses/>.
29 # Written by Eric Blake.
31 # In M4 1.4.x, every byte of $@ is rescanned. This means that an
32 # algorithm on n arguments that recurses with one less argument each
33 # iteration will scan n * (n + 1) / 2 arguments, for O(n^2) time. In
34 # M4 1.6, this was fixed so that $@ is only scanned once, then
35 # back-references are made to information stored about the scan.
36 # Thus, n iterations need only scan n arguments, for O(n) time.
37 # Additionally, in M4 1.4.x, recursive algorithms did not clean up
38 # memory very well, requiring O(n^2) memory rather than O(n) for n
39 # iterations.
40 #
41 # This file is designed to overcome the quadratic nature of $@
42 # recursion by writing a variant of m4_foreach that uses m4_for rather
43 # than $@ recursion to operate on the list. This involves more macro
44 # expansions, but avoids the need to rescan a quadratic number of
45 # arguments, making these replacements very attractive for M4 1.4.x.
46 # On the other hand, in any version of M4, expanding additional macros
47 # costs additional time; therefore, in M4 1.6, where $@ recursion uses
48 # fewer macros, these replacements actually pessimize performance.
49 # Additionally, the use of $10 to mean the tenth argument violates
50 # POSIX; although all versions of m4 1.4.x support this meaning, a
51 # future m4 version may switch to take it as the first argument
52 # concatenated with a literal 0, so the implementations in this file
53 # are not future-proof. Thus, this file is conditionally included as
54 # part of m4_init(), only when it is detected that M4 probably has
55 # quadratic behavior (ie. it lacks the macro __m4_version__).
56 #
57 # Please keep this file in sync with m4sugar.m4.
59 # _m4_foreach(PRE, POST, IGNORED, ARG...)
60 # ---------------------------------------
61 # Form the common basis of the m4_foreach and m4_map macros. For each
62 # ARG, expand PRE[ARG]POST[]. The IGNORED argument makes recursion
63 # easier, and must be supplied rather than implicit.
64 #
65 # This version minimizes the number of times that $@ is evaluated by
66 # using m4_for to generate a boilerplate into _m4_f then passing $@ to
67 # that temporary macro. Thus, the recursion is done in m4_for without
68 # reparsing any user input, and is not quadratic. For an idea of how
69 # this works, note that m4_foreach(i,[1,2],[i]) calls
70 # _m4_foreach([m4_define([i],],[)i],[],[1],[2])
71 # which defines _m4_f:
72 # $1[$4]$2[]$1[$5]$2[]_m4_popdef([_m4_f])
73 # then calls _m4_f([m4_define([i],],[)i],[],[1],[2]) for a net result:
74 # m4_define([i],[1])i[]m4_define([i],[2])i[]_m4_popdef([_m4_f]).
75 m4_define([_m4_foreach],
76 [m4_if([$#], [3], [],
77 [m4_pushdef([_m4_f], _m4_for([4], [$#], [1],
78 [$0_([1], [2],], [)])[_m4_popdef([_m4_f])])_m4_f($@)])])
80 m4_define([_m4_foreach_],
81 [[$$1[$$3]$$2[]]])
83 # m4_case(SWITCH, VAL1, IF-VAL1, VAL2, IF-VAL2, ..., DEFAULT)
84 # -----------------------------------------------------------
85 # Find the first VAL that SWITCH matches, and expand the corresponding
86 # IF-VAL. If there are no matches, expand DEFAULT.
87 #
88 # Use m4_for to create a temporary macro in terms of a boilerplate
89 # m4_if with final cleanup. If $# is even, we have DEFAULT; if it is
90 # odd, then rounding the last $# up in the temporary macro is
91 # harmless. For example, both m4_case(1,2,3,4,5) and
92 # m4_case(1,2,3,4,5,6) result in the intermediate _m4_case being
93 # m4_if([$1],[$2],[$3],[$1],[$4],[$5],_m4_popdef([_m4_case])[$6])
94 m4_define([m4_case],
95 [m4_if(m4_eval([$# <= 2]), [1], [$2],
96 [m4_pushdef([_$0], [m4_if(]_m4_for([2], m4_eval([($# - 1) / 2 * 2]), [2],
97 [_$0_(], [)])[_m4_popdef(
98 [_$0])]m4_dquote($m4_eval([($# + 1) & ~1]))[)])_$0($@)])])
100 m4_define([_m4_case_],
101 [$0_([1], [$1], m4_incr([$1]))])
103 m4_define([_m4_case__],
104 [[[$$1],[$$2],[$$3],]])
106 # m4_bmatch(SWITCH, RE1, VAL1, RE2, VAL2, ..., DEFAULT)
107 # -----------------------------------------------------
108 # m4 equivalent of
109 #
110 # if (SWITCH =~ RE1)
111 # VAL1;
112 # elif (SWITCH =~ RE2)
113 # VAL2;
114 # elif ...
115 # ...
116 # else
117 # DEFAULT
118 #
119 # We build the temporary macro _m4_b:
120 # m4_define([_m4_b], _m4_defn([_m4_bmatch]))_m4_b([$1], [$2], [$3])...
121 # _m4_b([$1], [$m-1], [$m])_m4_b([], [], [$m+1]_m4_popdef([_m4_b]))
122 # then invoke m4_unquote(_m4_b($@)), for concatenation with later text.
123 m4_define([m4_bmatch],
124 [m4_if([$#], 0, [m4_fatal([$0: too few arguments: $#])],
125 [$#], 1, [m4_fatal([$0: too few arguments: $#: $1])],
126 [$#], 2, [$2],
127 [m4_pushdef([_m4_b], [m4_define([_m4_b],
128 _m4_defn([_$0]))]_m4_for([3], m4_eval([($# + 1) / 2 * 2 - 1]),
129 [2], [_$0_(], [)])[_m4_b([], [],]m4_dquote([$]m4_eval(
130 [($# + 1) / 2 * 2]))[_m4_popdef([_m4_b]))])m4_unquote(_m4_b($@))])])
132 m4_define([_m4_bmatch],
133 [m4_if(m4_bregexp([$1], [$2]), [-1], [], [[$3]m4_define([$0])])])
135 m4_define([_m4_bmatch_],
136 [$0_([1], m4_decr([$1]), [$1])])
138 m4_define([_m4_bmatch__],
139 [[_m4_b([$$1], [$$2], [$$3])]])
142 # m4_cond(TEST1, VAL1, IF-VAL1, TEST2, VAL2, IF-VAL2, ..., [DEFAULT])
143 # -------------------------------------------------------------------
144 # Similar to m4_if, except that each TEST is expanded when encountered.
145 # If the expansion of TESTn matches the string VALn, the result is IF-VALn.
146 # The result is DEFAULT if no tests passed. This macro allows
147 # short-circuiting of expensive tests, where it pays to arrange quick
148 # filter tests to run first.
149 #
150 # m4_cond already guarantees either 3*n or 3*n + 1 arguments, 1 <= n.
151 # We only have to speed up _m4_cond, by building the temporary _m4_c:
152 # m4_define([_m4_c], _m4_defn([m4_unquote]))_m4_c([m4_if(($1), [($2)],
153 # [[$3]m4_define([_m4_c])])])_m4_c([m4_if(($4), [($5)],
154 # [[$6]m4_define([_m4_c])])])..._m4_c([m4_if(($m-2), [($m-1)],
155 # [[$m]m4_define([_m4_c])])])_m4_c([[$m+1]]_m4_popdef([_m4_c]))
156 # We invoke m4_unquote(_m4_c($@)), for concatenation with later text.
157 m4_define([_m4_cond],
158 [m4_pushdef([_m4_c], [m4_define([_m4_c],
159 _m4_defn([m4_unquote]))]_m4_for([2], m4_eval([$# / 3 * 3 - 1]), [3],
160 [$0_(], [)])[_m4_c(]m4_dquote(m4_dquote(
161 [$]m4_eval([$# / 3 * 3 + 1])))[_m4_popdef([_m4_c]))])m4_unquote(_m4_c($@))])
163 m4_define([_m4_cond_],
164 [$0_(m4_decr([$1]), [$1], m4_incr([$1]))])
166 m4_define([_m4_cond__],
167 [[_m4_c([m4_if(($$1), [($$2)], [[$$3]m4_define([_m4_c])])])]])
169 # m4_bpatsubsts(STRING, RE1, SUBST1, RE2, SUBST2, ...)
170 # ----------------------------------------------------
171 # m4 equivalent of
172 #
173 # $_ = STRING;
174 # s/RE1/SUBST1/g;
175 # s/RE2/SUBST2/g;
176 # ...
177 #
178 # m4_bpatsubsts already validated an odd number of arguments; we only
179 # need to speed up _m4_bpatsubsts. To avoid nesting, we build the
180 # temporary _m4_p:
181 # m4_define([_m4_p], [$1])m4_define([_m4_p],
182 # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$2], [$3]))m4_define([_m4_p],
183 # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$4], [$5]))m4_define([_m4_p],...
184 # m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$m-1], [$m]))m4_unquote(
185 # _m4_defn([_m4_p])_m4_popdef([_m4_p]))
186 m4_define([_m4_bpatsubsts],
187 [m4_pushdef([_m4_p], [m4_define([_m4_p],
188 ]m4_dquote([$]1)[)]_m4_for([3], [$#], [2], [$0_(],
189 [)])[m4_unquote(_m4_defn([_m4_p])_m4_popdef([_m4_p]))])_m4_p($@)])
191 m4_define([_m4_bpatsubsts_],
192 [$0_(m4_decr([$1]), [$1])])
194 m4_define([_m4_bpatsubsts__],
195 [[m4_define([_m4_p],
196 m4_bpatsubst(m4_dquote(_m4_defn([_m4_p])), [$$1], [$$2]))]])
198 # m4_shiftn(N, ...)
199 # -----------------
200 # Returns ... shifted N times. Useful for recursive "varargs" constructs.
201 #
202 # m4_shiftn already validated arguments; we only need to speed up
203 # _m4_shiftn. If N is 3, then we build the temporary _m4_s, defined as
204 # ,[$5],[$6],...,[$m]_m4_popdef([_m4_s])
205 # before calling m4_shift(_m4_s($@)).
206 m4_define([_m4_shiftn],
207 [m4_if(m4_incr([$1]), [$#], [], [m4_pushdef([_m4_s],
208 _m4_for(m4_eval([$1 + 2]), [$#], [1],
209 [[,]m4_dquote($], [)])[_m4_popdef([_m4_s])])m4_shift(_m4_s($@))])])
211 # m4_do(STRING, ...)
212 # ------------------
213 # This macro invokes all its arguments (in sequence, of course). It is
214 # useful for making your macros more structured and readable by dropping
215 # unnecessary dnl's and have the macros indented properly.
216 #
217 # Here, we use the temporary macro _m4_do, defined as
218 # $1[]$2[]...[]$n[]_m4_popdef([_m4_do])
219 m4_define([m4_do],
220 [m4_if([$#], [0], [],
221 [m4_pushdef([_$0], _m4_for([1], [$#], [1],
222 [$], [[[]]])[_m4_popdef([_$0])])_$0($@)])])
224 # m4_dquote_elt(ARGS)
225 # -------------------
226 # Return ARGS as an unquoted list of double-quoted arguments.
227 #
228 # _m4_foreach to the rescue.
229 m4_define([m4_dquote_elt],
230 [m4_if([$#], [0], [], [[[$1]]_m4_foreach([,m4_dquote(], [)], $@)])])
232 # m4_reverse(ARGS)
233 # ----------------
234 # Output ARGS in reverse order.
235 #
236 # Invoke _m4_r($@) with the temporary _m4_r built as
237 # [$m], [$m-1], ..., [$2], [$1]_m4_popdef([_m4_r])
238 m4_define([m4_reverse],
239 [m4_if([$#], [0], [], [$#], [1], [[$1]],
240 [m4_pushdef([_m4_r], [[$$#]]_m4_for(m4_decr([$#]), [1], [-1],
241 [[, ]m4_dquote($], [)])[_m4_popdef([_m4_r])])_m4_r($@)])])
244 # m4_map_args_pair(EXPRESSION, [END-EXPR = EXPRESSION], ARG...)
245 # -------------------------------------------------------------
246 # Perform a pairwise grouping of consecutive ARGs, by expanding
247 # EXPRESSION([ARG1], [ARG2]). If there are an odd number of ARGs, the
248 # final argument is expanded with END-EXPR([ARGn]).
249 #
250 # Build the temporary macro _m4_map_args_pair, with the $2([$m+1])
251 # only output if $# is odd:
252 # $1([$3], [$4])[]$1([$5], [$6])[]...$1([$m-1],
253 # [$m])[]m4_default([$2], [$1])([$m+1])[]_m4_popdef([_m4_map_args_pair])
254 m4_define([m4_map_args_pair],
255 [m4_if([$#], [0], [m4_fatal([$0: too few arguments: $#])],
256 [$#], [1], [m4_fatal([$0: too few arguments: $#: $1])],
257 [$#], [2], [],
258 [$#], [3], [m4_default([$2], [$1])([$3])[]],
259 [m4_pushdef([_$0], _m4_for([3],
260 m4_eval([$# / 2 * 2 - 1]), [2], [_$0_(], [)])_$0_end(
261 [1], [2], [$#])[_m4_popdef([_$0])])_$0($@)])])
263 m4_define([_m4_map_args_pair_],
264 [$0_([1], [$1], m4_incr([$1]))])
266 m4_define([_m4_map_args_pair__],
267 [[$$1([$$2], [$$3])[]]])
269 m4_define([_m4_map_args_pair_end],
270 [m4_if(m4_eval([$3 & 1]), [1], [[m4_default([$$2], [$$1])([$$3])[]]])])
272 # m4_join(SEP, ARG1, ARG2...)
273 # ---------------------------
274 # Produce ARG1SEPARG2...SEPARGn. Avoid back-to-back SEP when a given ARG
275 # is the empty string. No expansion is performed on SEP or ARGs.
276 #
277 # Use a self-modifying separator, since we don't know how many
278 # arguments might be skipped before a separator is first printed, but
279 # be careful if the separator contains $. _m4_foreach to the rescue.
280 m4_define([m4_join],
281 [m4_pushdef([_m4_sep], [m4_define([_m4_sep], _m4_defn([m4_echo]))])]dnl
282 [_m4_foreach([_$0([$1],], [)], $@)_m4_popdef([_m4_sep])])
284 m4_define([_m4_join],
285 [m4_if([$2], [], [], [_m4_sep([$1])[$2]])])
287 # m4_joinall(SEP, ARG1, ARG2...)
288 # ------------------------------
289 # Produce ARG1SEPARG2...SEPARGn. An empty ARG results in back-to-back SEP.
290 # No expansion is performed on SEP or ARGs.
291 #
292 # A bit easier than m4_join. _m4_foreach to the rescue.
293 m4_define([m4_joinall],
294 [[$2]m4_if(m4_eval([$# <= 2]), [1], [],
295 [_m4_foreach([$1], [], m4_shift($@))])])
297 # m4_list_cmp(A, B)
298 # -----------------
299 # Compare the two lists of integer expressions A and B.
300 #
301 # m4_list_cmp takes care of any side effects; we only override
302 # _m4_list_cmp_raw, where we can safely expand lists multiple times.
303 # First, insert padding so that both lists are the same length; the
304 # trailing +0 is necessary to handle a missing list. Next, create a
305 # temporary macro to perform pairwise comparisons until an inequality
306 # is found. For example, m4_list_cmp([1], [1,2]) creates _m4_cmp as
307 # m4_if(m4_eval([($1) != ($3)]), [1], [m4_cmp([$1], [$3])],
308 # m4_eval([($2) != ($4)]), [1], [m4_cmp([$2], [$4])],
309 # [0]_m4_popdef([_m4_cmp]))
310 # then calls _m4_cmp([1+0], [0*2], [1], [2+0])
311 m4_define([_m4_list_cmp_raw],
312 [m4_if([$1], [$2], 0,
313 [_m4_list_cmp($1+0_m4_list_pad(m4_count($1), m4_count($2)),
314 $2+0_m4_list_pad(m4_count($2), m4_count($1)))])])
316 m4_define([_m4_list_pad],
317 [m4_if(m4_eval($1 < $2), [1],
318 [_m4_for(m4_incr([$1]), [$2], [1], [,0*])])])
320 m4_define([_m4_list_cmp],
321 [m4_pushdef([_m4_cmp], [m4_if(]_m4_for(
322 [1], m4_eval([$# >> 1]), [1], [$0_(], [,]m4_eval([$# >> 1])[)])[
323 [0]_m4_popdef([_m4_cmp]))])_m4_cmp($@)])
325 m4_define([_m4_list_cmp_],
326 [$0_([$1], m4_eval([$1 + $2]))])
328 m4_define([_m4_list_cmp__],
329 [[m4_eval([($$1) != ($$2)]), [1], [m4_cmp([$$1], [$$2])],
330 ]])
332 # m4_max(EXPR, ...)
333 # m4_min(EXPR, ...)
334 # -----------------
335 # Return the decimal value of the maximum (or minimum) in a series of
336 # integer expressions.
337 #
338 # _m4_foreach to the rescue; we only need to replace _m4_minmax. Here,
339 # we need a temporary macro to track the best answer so far, so that
340 # the foreach expression is tractable.
341 m4_define([_m4_minmax],
342 [m4_pushdef([_m4_best], m4_eval([$2]))_m4_foreach(
343 [m4_define([_m4_best], $1(_m4_best,], [))], m4_shift($@))]dnl
344 [_m4_best[]_m4_popdef([_m4_best])])
346 # m4_set_add_all(SET, VALUE...)
347 # -----------------------------
348 # Add each VALUE into SET. This is O(n) in the number of VALUEs, and
349 # can be faster than calling m4_set_add for each VALUE.
350 #
351 # _m4_foreach to the rescue. If no deletions have occurred, then
352 # avoid the speed penalty of m4_set_add.
353 m4_define([m4_set_add_all],
354 [m4_if([$#], [0], [], [$#], [1], [],
355 [m4_define([_m4_set_size($1)], m4_eval(m4_set_size([$1])
356 + m4_len(_m4_foreach(m4_ifdef([_m4_set_cleanup($1)],
357 [[m4_set_add]], [[_$0]])[([$1],], [)], $@))))])])
359 m4_define([_m4_set_add_all],
360 [m4_ifdef([_m4_set([$1],$2)], [],
361 [m4_define([_m4_set([$1],$2)],
362 [1])m4_pushdef([_m4_set([$1])], [$2])-])])