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Commit | Line | Data |
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6780ca7a DM |
1 | Bison News |
2 | ---------- | |
3af4feb2 | 3 | |
35fe0834 PE |
4 | Changes in version 2.3a+ (????-??-??): |
5 | ||
6 | * The -g and --graph options now output graphs in Graphviz DOT format, | |
7 | not VCG format. | |
8 | ||
0e021770 PE |
9 | * An experimental directive %language specifies the language of the |
10 | generated parser, which can be C (the default) or C++. This | |
11 | directive affects the skeleton used, and the names of the generated | |
12 | files if the grammar file's name ends in ".y". | |
13 | ||
02975b9a JD |
14 | * The grammar file may now specify the name of the parser header file using |
15 | %defines. For example: | |
16 | ||
17 | %defines "parser.h" | |
18 | ||
16dc6a9e | 19 | * The `=' that used to be required in the following directives is now |
02975b9a JD |
20 | deprecated: |
21 | ||
22 | %file-prefix "parser" | |
23 | %name-prefix "c_" | |
24 | %output "parser.c" | |
25 | ||
16dc6a9e JD |
26 | * The quotes around NAME that used to be required in the following directive |
27 | are now deprecated: | |
28 | ||
29 | %define NAME "VALUE" | |
30 | ||
8e0a5e9e JD |
31 | * Bison 2.3a provided a new set of directives as a more flexible alternative to |
32 | the traditional Yacc prologue blocks. Those have now been consolidated into | |
33 | a single %code directive with an optional qualifier field, which identifies | |
34 | the purpose of the code and thus the location(s) where Bison should generate | |
35 | it: | |
36 | ||
16dc6a9e JD |
37 | 1. `%code {CODE}' replaces `%after-header {CODE}' |
38 | 2. `%code requires {CODE}' replaces `%start-header {CODE}' | |
39 | 3. `%code provides {CODE}' replaces `%end-header {CODE}' | |
40 | 4. `%code top {CODE}' replaces `%before-header {CODE}' | |
8e0a5e9e JD |
41 | |
42 | See the %code entries in `Appendix A Bison Symbols' in the Bison manual for a | |
43 | summary of the new functionality. See the new section `Prologue | |
44 | Alternatives' for a detailed discussion including the advantages of %code | |
45 | over the traditional Yacc prologues. | |
46 | ||
47 | The prologue alternatives are experimental. More user feedback will help to | |
48 | determine whether they should become permanent features. | |
49 | ||
17bd8a73 JD |
50 | * Revised warning: unset or unused mid-rule values |
51 | ||
52 | Since Bison 2.2, Bison has warned about mid-rule values that are set but not | |
53 | used within any of the actions of the parent rule. For example, Bison warns | |
54 | about unused $2 in: | |
55 | ||
56 | exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; }; | |
57 | ||
58 | Now, Bison also warns about mid-rule values that are used but not set. For | |
59 | example, Bison warns about unset $$ in the mid-rule action in: | |
60 | ||
61 | exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; }; | |
62 | ||
63 | However, Bison now disables both of these warnings by default since they | |
64 | sometimes prove to be false alarms in existing grammars employing the Yacc | |
65 | constructs $0 or $-N (where N is some positive integer). | |
66 | ||
67 | To enable these warnings, specify the flag `--warnings=midrule-values' or | |
68 | `-W', which is a synonym for `--warnings=all'. | |
69 | ||
12e35840 JD |
70 | * Bison now recognizes two separate kinds of default %destructor's and |
71 | %printer's: | |
72 | ||
73 | 1. Place `<*>' in a %destructor/%printer symbol list to define a default | |
74 | %destructor/%printer for all grammar symbols for which you have formally | |
75 | declared semantic type tags. | |
76 | ||
3ebecc24 | 77 | 2. Place `<>' in a %destructor/%printer symbol list to define a default |
12e35840 JD |
78 | %destructor/%printer for all grammar symbols without declared semantic |
79 | type tags. | |
80 | ||
81 | Bison no longer supports the `%symbol-default' notation from Bison 2.3a. | |
3ebecc24 | 82 | `<*>' and `<>' combined achieve the same effect with one exception: Bison no |
12e35840 JD |
83 | longer applies any %destructor to a mid-rule value if that mid-rule value is |
84 | not actually ever referenced using either $$ or $n in a semantic action. | |
85 | ||
85894313 JD |
86 | The default %destructor's and %printer's are experimental. More user |
87 | feedback will help to determine whether they should become permanent | |
88 | features. | |
89 | ||
12e35840 JD |
90 | See the section `Freeing Discarded Symbols' in the Bison manual for further |
91 | details. | |
92 | ||
21fe08ca | 93 | Changes in version 2.3a, 2006-09-13: |
742e4900 | 94 | |
ddc8ede1 PE |
95 | * Instead of %union, you can define and use your own union type |
96 | YYSTYPE if your grammar contains at least one <type> tag. | |
97 | Your YYSTYPE need not be a macro; it can be a typedef. | |
98 | This change is for compatibility with other Yacc implementations, | |
99 | and is required by POSIX. | |
100 | ||
cd48d21d AD |
101 | * Locations columns and lines start at 1. |
102 | In accordance with the GNU Coding Standards and Emacs. | |
103 | ||
b2a0b7ca | 104 | * You may now declare per-type and default %destructor's and %printer's: |
ec5479ce JD |
105 | |
106 | For example: | |
107 | ||
b2a0b7ca JD |
108 | %union { char *string; } |
109 | %token <string> STRING1 | |
110 | %token <string> STRING2 | |
111 | %type <string> string1 | |
112 | %type <string> string2 | |
113 | %union { char character; } | |
114 | %token <character> CHR | |
115 | %type <character> chr | |
116 | %destructor { free ($$); } %symbol-default | |
117 | %destructor { free ($$); printf ("%d", @$.first_line); } STRING1 string1 | |
118 | %destructor { } <character> | |
119 | ||
120 | guarantees that, when the parser discards any user-defined symbol that has a | |
121 | semantic type tag other than `<character>', it passes its semantic value to | |
122 | `free'. However, when the parser discards a `STRING1' or a `string1', it | |
123 | also prints its line number to `stdout'. It performs only the second | |
124 | `%destructor' in this case, so it invokes `free' only once. | |
ec5479ce | 125 | |
85894313 JD |
126 | [Although we failed to mention this here in the 2.3a release, the default |
127 | %destructor's and %printer's were experimental, and they were rewritten in | |
128 | future versions.] | |
129 | ||
b931235e JD |
130 | * Except for LALR(1) parsers in C with POSIX Yacc emulation enabled (with `-y', |
131 | `--yacc', or `%yacc'), Bison no longer generates #define statements for | |
132 | associating token numbers with token names. Removing the #define statements | |
133 | helps to sanitize the global namespace during preprocessing, but POSIX Yacc | |
134 | requires them. Bison still generates an enum for token names in all cases. | |
135 | ||
34f98f46 JD |
136 | * Handling of traditional Yacc prologue blocks is now more consistent but |
137 | potentially incompatible with previous releases of Bison. | |
9bc0dd67 JD |
138 | |
139 | As before, you declare prologue blocks in your grammar file with the | |
140 | `%{ ... %}' syntax. To generate the pre-prologue, Bison concatenates all | |
34f98f46 JD |
141 | prologue blocks that you've declared before the first %union. To generate |
142 | the post-prologue, Bison concatenates all prologue blocks that you've | |
ddc8ede1 | 143 | declared after the first %union. |
9bc0dd67 | 144 | |
34f98f46 | 145 | Previous releases of Bison inserted the pre-prologue into both the header |
9bc0dd67 JD |
146 | file and the code file in all cases except for LALR(1) parsers in C. In the |
147 | latter case, Bison inserted it only into the code file. For parsers in C++, | |
148 | the point of insertion was before any token definitions (which associate | |
149 | token numbers with names). For parsers in C, the point of insertion was | |
150 | after the token definitions. | |
151 | ||
152 | Now, Bison never inserts the pre-prologue into the header file. In the code | |
153 | file, it always inserts it before the token definitions. | |
154 | ||
34f98f46 JD |
155 | * Bison now provides a more flexible alternative to the traditional Yacc |
156 | prologue blocks: %before-header, %start-header, %end-header, and | |
157 | %after-header. | |
158 | ||
159 | For example, the following declaration order in the grammar file reflects the | |
160 | order in which Bison will output these code blocks. However, you are free to | |
161 | declare these code blocks in your grammar file in whatever order is most | |
162 | convenient for you: | |
163 | ||
164 | %before-header { | |
165 | /* Bison treats this block like a pre-prologue block: it inserts it into | |
166 | * the code file before the contents of the header file. It does *not* | |
167 | * insert it into the header file. This is a good place to put | |
168 | * #include's that you want at the top of your code file. A common | |
169 | * example is `#include "system.h"'. */ | |
170 | } | |
171 | %start-header { | |
172 | /* Bison inserts this block into both the header file and the code file. | |
173 | * In both files, the point of insertion is before any Bison-generated | |
174 | * token, semantic type, location type, and class definitions. This is a | |
175 | * good place to define %union dependencies, for example. */ | |
9bc0dd67 JD |
176 | } |
177 | %union { | |
34f98f46 JD |
178 | /* Unlike the traditional Yacc prologue blocks, the output order for the |
179 | * new %*-header blocks is not affected by their declaration position | |
180 | * relative to any %union in the grammar file. */ | |
9bc0dd67 | 181 | } |
34f98f46 JD |
182 | %end-header { |
183 | /* Bison inserts this block into both the header file and the code file. | |
184 | * In both files, the point of insertion is after the Bison-generated | |
185 | * definitions. This is a good place to declare or define public | |
186 | * functions or data structures that depend on the Bison-generated | |
187 | * definitions. */ | |
9bc0dd67 | 188 | } |
34f98f46 JD |
189 | %after-header { |
190 | /* Bison treats this block like a post-prologue block: it inserts it into | |
191 | * the code file after the contents of the header file. It does *not* | |
192 | * insert it into the header file. This is a good place to declare or | |
193 | * define internal functions or data structures that depend on the | |
194 | * Bison-generated definitions. */ | |
195 | } | |
196 | ||
197 | If you have multiple occurrences of any one of the above declarations, Bison | |
198 | will concatenate the contents in declaration order. | |
9bc0dd67 | 199 | |
85894313 JD |
200 | [Although we failed to mention this here in the 2.3a release, the prologue |
201 | alternatives were experimental, and they were rewritten in future versions.] | |
202 | ||
742e4900 | 203 | * The option `--report=look-ahead' has been changed to `--report=lookahead'. |
9e6e7ed2 PE |
204 | The old spelling still works, but is not documented and may be removed |
205 | in a future release. | |
742e4900 | 206 | |
4ad3ed84 PE |
207 | Changes in version 2.3, 2006-06-05: |
208 | ||
209 | * GLR grammars should now use `YYRECOVERING ()' instead of `YYRECOVERING', | |
210 | for compatibility with LALR(1) grammars. | |
211 | ||
212 | * It is now documented that any definition of YYSTYPE or YYLTYPE should | |
213 | be to a type name that does not contain parentheses or brackets. | |
214 | ||
ab8d9dc5 | 215 | Changes in version 2.2, 2006-05-19: |
193d7c70 PE |
216 | |
217 | * The distribution terms for all Bison-generated parsers now permit | |
218 | using the parsers in nonfree programs. Previously, this permission | |
219 | was granted only for Bison-generated LALR(1) parsers in C. | |
5f4236a0 | 220 | |
aa08666d AD |
221 | * %name-prefix changes the namespace name in C++ outputs. |
222 | ||
223 | * The C++ parsers export their token_type. | |
5f4236a0 | 224 | |
d6ca7905 PE |
225 | * Bison now allows multiple %union declarations, and concatenates |
226 | their contents together. | |
227 | ||
affac613 | 228 | * New warning: unused values |
4d7bc38c PE |
229 | Right-hand side symbols whose values are not used are reported, |
230 | if the symbols have destructors. For instance: | |
affac613 | 231 | |
8f3596a6 | 232 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; } |
721be13c PE |
233 | | exp "+" exp |
234 | ; | |
affac613 | 235 | |
8f3596a6 AD |
236 | will trigger a warning about $$ and $5 in the first rule, and $3 in |
237 | the second ($1 is copied to $$ by the default rule). This example | |
4e26c69e | 238 | most likely contains three errors, and could be rewritten as: |
affac613 | 239 | |
4e26c69e PE |
240 | exp: exp "?" exp ":" exp |
241 | { $$ = $1 ? $3 : $5; free ($1 ? $5 : $3); free ($1); } | |
242 | | exp "+" exp | |
243 | { $$ = $1 ? $1 : $3; if ($1) free ($3); } | |
721be13c | 244 | ; |
affac613 | 245 | |
4e26c69e PE |
246 | However, if the original actions were really intended, memory leaks |
247 | and all, the warnings can be suppressed by letting Bison believe the | |
248 | values are used, e.g.: | |
721be13c | 249 | |
8f3596a6 | 250 | exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); } |
721be13c PE |
251 | | exp "+" exp { $$ = $1; (void) $3; } |
252 | ; | |
253 | ||
84866159 AD |
254 | If there are mid-rule actions, the warning is issued if no action |
255 | uses it. The following triggers no warning: $1 and $3 are used. | |
256 | ||
257 | exp: exp { push ($1); } '+' exp { push ($3); sum (); }; | |
258 | ||
721be13c PE |
259 | The warning is intended to help catching lost values and memory leaks. |
260 | If a value is ignored, its associated memory typically is not reclaimed. | |
affac613 | 261 | |
9d9b8b70 PE |
262 | * %destructor vs. YYABORT, YYACCEPT, and YYERROR. |
263 | Destructors are now called when user code invokes YYABORT, YYACCEPT, | |
264 | and YYERROR, for all objects on the stack, other than objects | |
265 | corresponding to the right-hand side of the current rule. | |
a85284cf | 266 | |
035aa4a0 PE |
267 | * %expect, %expect-rr |
268 | Incorrect numbers of expected conflicts are now actual errors, | |
269 | instead of warnings. | |
270 | ||
4b367315 | 271 | * GLR, YACC parsers. |
4e26c69e PE |
272 | The %parse-params are available in the destructors (and the |
273 | experimental printers) as per the documentation. | |
4b367315 | 274 | |
302c0aee | 275 | * Bison now warns if it finds a stray `$' or `@' in an action. |
ad6a9b97 | 276 | |
b50d2359 | 277 | * %require "VERSION" |
4e26c69e PE |
278 | This specifies that the grammar file depends on features implemented |
279 | in Bison version VERSION or higher. | |
b50d2359 | 280 | |
fb9712a9 | 281 | * lalr1.cc: The token and value types are now class members. |
e14d0ab6 AD |
282 | The tokens were defined as free form enums and cpp macros. YYSTYPE |
283 | was defined as a free form union. They are now class members: | |
fb9712a9 AD |
284 | tokens are enumerations of the `yy::parser::token' struct, and the |
285 | semantic values have the `yy::parser::semantic_type' type. | |
286 | ||
287 | If you do not want or can update to this scheme, the directive | |
288 | `%define "global_tokens_and_yystype" "1"' triggers the global | |
b50d2359 AD |
289 | definition of tokens and YYSTYPE. This change is suitable both |
290 | for previous releases of Bison, and this one. | |
fb9712a9 | 291 | |
b50d2359 | 292 | If you wish to update, then make sure older version of Bison will |
ab8d9dc5 | 293 | fail using `%require "2.2"'. |
fb9712a9 | 294 | |
302c0aee | 295 | * DJGPP support added. |
193d7c70 | 296 | \f |
1bd0deda | 297 | Changes in version 2.1, 2005-09-16: |
1ce59070 | 298 | |
e14d0ab6 AD |
299 | * The C++ lalr1.cc skeleton supports %lex-param. |
300 | ||
a7db4add | 301 | * Bison-generated parsers now support the translation of diagnostics like |
baf785db PE |
302 | "syntax error" into languages other than English. The default |
303 | language is still English. For details, please see the new | |
0410a6e0 PE |
304 | Internationalization section of the Bison manual. Software |
305 | distributors should also see the new PACKAGING file. Thanks to | |
306 | Bruno Haible for this new feature. | |
1ce59070 | 307 | |
1a059451 PE |
308 | * Wording in the Bison-generated parsers has been changed slightly to |
309 | simplify translation. In particular, the message "memory exhausted" | |
310 | has replaced "parser stack overflow", as the old message was not | |
311 | always accurate for modern Bison-generated parsers. | |
312 | ||
258b75ca PE |
313 | * Destructors are now called when the parser aborts, for all symbols left |
314 | behind on the stack. Also, the start symbol is now destroyed after a | |
315 | successful parse. In both cases, the behavior was formerly inconsistent. | |
316 | ||
a7db4add | 317 | * When generating verbose diagnostics, Bison-generated parsers no longer |
72f000b0 PE |
318 | quote the literal strings associated with tokens. For example, for |
319 | a syntax error associated with '%token NUM "number"' they might | |
320 | print 'syntax error, unexpected number' instead of 'syntax error, | |
321 | unexpected "number"'. | |
193d7c70 | 322 | \f |
82de6b0d | 323 | Changes in version 2.0, 2004-12-25: |
efeed023 | 324 | |
82de6b0d | 325 | * Possibly-incompatible changes |
d7e14fc0 | 326 | |
82de6b0d PE |
327 | - Bison-generated parsers no longer default to using the alloca function |
328 | (when available) to extend the parser stack, due to widespread | |
329 | problems in unchecked stack-overflow detection. You can "#define | |
330 | YYSTACK_USE_ALLOCA 1" to require the use of alloca, but please read | |
331 | the manual to determine safe values for YYMAXDEPTH in that case. | |
8dd162d3 | 332 | |
82de6b0d PE |
333 | - Error token location. |
334 | During error recovery, the location of the syntax error is updated | |
335 | to cover the whole sequence covered by the error token: it includes | |
336 | the shifted symbols thrown away during the first part of the error | |
337 | recovery, and the lookahead rejected during the second part. | |
18d192f0 | 338 | |
82de6b0d PE |
339 | - Semicolon changes: |
340 | . Stray semicolons are no longer allowed at the start of a grammar. | |
341 | . Semicolons are now required after in-grammar declarations. | |
e342c3be | 342 | |
82de6b0d PE |
343 | - Unescaped newlines are no longer allowed in character constants or |
344 | string literals. They were never portable, and GCC 3.4.0 has | |
345 | dropped support for them. Better diagnostics are now generated if | |
346 | forget a closing quote. | |
8dd162d3 | 347 | |
82de6b0d | 348 | - NUL bytes are no longer allowed in Bison string literals, unfortunately. |
f74b6f91 | 349 | |
82de6b0d | 350 | * New features |
1452af69 | 351 | |
82de6b0d | 352 | - GLR grammars now support locations. |
4febdd96 | 353 | |
82de6b0d PE |
354 | - New directive: %initial-action. |
355 | This directive allows the user to run arbitrary code (including | |
356 | initializing @$) from yyparse before parsing starts. | |
1452af69 | 357 | |
82de6b0d PE |
358 | - A new directive "%expect-rr N" specifies the expected number of |
359 | reduce/reduce conflicts in GLR parsers. | |
1452af69 | 360 | |
82de6b0d PE |
361 | - %token numbers can now be hexadecimal integers, e.g., `%token FOO 0x12d'. |
362 | This is a GNU extension. | |
4febdd96 | 363 | |
82de6b0d | 364 | - The option `--report=lookahead' was changed to `--report=look-ahead'. |
9e6e7ed2 | 365 | [However, this was changed back after 2.3.] |
1452af69 | 366 | |
82de6b0d | 367 | - Experimental %destructor support has been added to lalr1.cc. |
1452af69 | 368 | |
82de6b0d PE |
369 | - New configure option --disable-yacc, to disable installation of the |
370 | yacc command and -ly library introduced in 1.875 for POSIX conformance. | |
6040d338 | 371 | |
82de6b0d | 372 | * Bug fixes |
d5a3fe37 | 373 | |
82de6b0d PE |
374 | - For now, %expect-count violations are now just warnings, not errors. |
375 | This is for compatibility with Bison 1.75 and earlier (when there are | |
376 | reduce/reduce conflicts) and with Bison 1.30 and earlier (when there | |
377 | are too many or too few shift/reduce conflicts). However, in future | |
378 | versions of Bison we plan to improve the %expect machinery so that | |
379 | these violations will become errors again. | |
3473d0f8 | 380 | |
82de6b0d PE |
381 | - Within Bison itself, numbers (e.g., goto numbers) are no longer |
382 | arbitrarily limited to 16-bit counts. | |
d600ee67 | 383 | |
82de6b0d | 384 | - Semicolons are now allowed before "|" in grammar rules, as POSIX requires. |
d600ee67 | 385 | \f |
dc546b0f | 386 | Changes in version 1.875, 2003-01-01: |
963fcc17 | 387 | |
dc546b0f PE |
388 | * The documentation license has been upgraded to version 1.2 |
389 | of the GNU Free Documentation License. | |
75eb3bc4 | 390 | |
dc546b0f | 391 | * syntax error processing |
75eb3bc4 | 392 | |
dc546b0f PE |
393 | - In Yacc-style parsers YYLLOC_DEFAULT is now used to compute error |
394 | locations too. This fixes bugs in error-location computation. | |
75eb3bc4 | 395 | |
dc546b0f PE |
396 | - %destructor |
397 | It is now possible to reclaim the memory associated to symbols | |
398 | discarded during error recovery. This feature is still experimental. | |
20daca06 | 399 | |
dc546b0f PE |
400 | - %error-verbose |
401 | This new directive is preferred over YYERROR_VERBOSE. | |
74724a70 | 402 | |
dc546b0f PE |
403 | - #defining yyerror to steal internal variables is discouraged. |
404 | It is not guaranteed to work forever. | |
d1de5372 | 405 | |
dc546b0f | 406 | * POSIX conformance |
d1de5372 | 407 | |
dc546b0f PE |
408 | - Semicolons are once again optional at the end of grammar rules. |
409 | This reverts to the behavior of Bison 1.33 and earlier, and improves | |
410 | compatibility with Yacc. | |
74724a70 | 411 | |
dc546b0f PE |
412 | - `parse error' -> `syntax error' |
413 | Bison now uniformly uses the term `syntax error'; formerly, the code | |
414 | and manual sometimes used the term `parse error' instead. POSIX | |
415 | requires `syntax error' in diagnostics, and it was thought better to | |
416 | be consistent. | |
74724a70 | 417 | |
dc546b0f PE |
418 | - The documentation now emphasizes that yylex and yyerror must be |
419 | declared before use. C99 requires this. | |
d1de5372 | 420 | |
dc546b0f PE |
421 | - Bison now parses C99 lexical constructs like UCNs and |
422 | backslash-newline within C escape sequences, as POSIX 1003.1-2001 requires. | |
d1de5372 | 423 | |
dc546b0f PE |
424 | - File names are properly escaped in C output. E.g., foo\bar.y is |
425 | output as "foo\\bar.y". | |
6780ca7a | 426 | |
dc546b0f PE |
427 | - Yacc command and library now available |
428 | The Bison distribution now installs a `yacc' command, as POSIX requires. | |
429 | Also, Bison now installs a small library liby.a containing | |
430 | implementations of Yacc-compatible yyerror and main functions. | |
431 | This library is normally not useful, but POSIX requires it. | |
6e649e65 | 432 | |
dc546b0f | 433 | - Type clashes now generate warnings, not errors. |
6e649e65 | 434 | |
dc546b0f PE |
435 | - If the user does not define YYSTYPE as a macro, Bison now declares it |
436 | using typedef instead of defining it as a macro. | |
437 | For consistency, YYLTYPE is also declared instead of defined. | |
9501dc6e | 438 | |
dc546b0f | 439 | * Other compatibility issues |
886a425c | 440 | |
dc546b0f PE |
441 | - %union directives can now have a tag before the `{', e.g., the |
442 | directive `%union foo {...}' now generates the C code | |
443 | `typedef union foo { ... } YYSTYPE;'; this is for Yacc compatibility. | |
444 | The default union tag is `YYSTYPE', for compatibility with Solaris 9 Yacc. | |
445 | For consistency, YYLTYPE's struct tag is now `YYLTYPE' not `yyltype'. | |
446 | This is for compatibility with both Yacc and Bison 1.35. | |
72f889cc | 447 | |
dc546b0f PE |
448 | - `;' is output before the terminating `}' of an action, for |
449 | compatibility with Bison 1.35. | |
886a425c | 450 | |
dc546b0f PE |
451 | - Bison now uses a Yacc-style format for conflict reports, e.g., |
452 | `conflicts: 2 shift/reduce, 1 reduce/reduce'. | |
437c2d80 | 453 | |
dc546b0f PE |
454 | - `yystype' and `yyltype' are now obsolescent macros instead of being |
455 | typedefs or tags; they are no longer documented and are planned to be | |
456 | withdrawn in a future release. | |
2a8d363a | 457 | |
dc546b0f | 458 | * GLR parser notes |
2a8d363a | 459 | |
dc546b0f PE |
460 | - GLR and inline |
461 | Users of Bison have to decide how they handle the portability of the | |
462 | C keyword `inline'. | |
959e5f51 | 463 | |
dc546b0f PE |
464 | - `parsing stack overflow...' -> `parser stack overflow' |
465 | GLR parsers now report `parser stack overflow' as per the Bison manual. | |
900c5db5 | 466 | |
dc546b0f PE |
467 | * Bison now warns if it detects conflicting outputs to the same file, |
468 | e.g., it generates a warning for `bison -d -o foo.h foo.y' since | |
469 | that command outputs both code and header to foo.h. | |
6e40b4eb | 470 | |
dc546b0f PE |
471 | * #line in output files |
472 | - --no-line works properly. | |
6e40b4eb AD |
473 | |
474 | * Bison can no longer be built by a K&R C compiler; it requires C89 or | |
475 | later to be built. This change originally took place a few versions | |
476 | ago, but nobody noticed until we recently asked someone to try | |
477 | building Bison with a K&R C compiler. | |
d600ee67 | 478 | \f |
5c16c6b1 | 479 | Changes in version 1.75, 2002-10-14: |
7933f2b5 PE |
480 | |
481 | * Bison should now work on 64-bit hosts. | |
482 | ||
b7195100 | 483 | * Indonesian translation thanks to Tedi Heriyanto. |
7933f2b5 | 484 | |
f50adbbd AD |
485 | * GLR parsers |
486 | Fix spurious parse errors. | |
487 | ||
488 | * Pure parsers | |
489 | Some people redefine yyerror to steal yyparse' private variables. | |
490 | Reenable this trick until an official feature replaces it. | |
491 | ||
d90c934c AD |
492 | * Type Clashes |
493 | In agreement with POSIX and with other Yaccs, leaving a default | |
494 | action is valid when $$ is untyped, and $1 typed: | |
495 | ||
496 | untyped: ... typed; | |
497 | ||
498 | but the converse remains an error: | |
499 | ||
500 | typed: ... untyped; | |
501 | ||
502 | * Values of mid-rule actions | |
503 | The following code: | |
504 | ||
505 | foo: { ... } { $$ = $1; } ... | |
506 | ||
507 | was incorrectly rejected: $1 is defined in the second mid-rule | |
508 | action, and is equal to the $$ of the first mid-rule action. | |
d600ee67 | 509 | \f |
420f93c8 | 510 | Changes in version 1.50, 2002-10-04: |
adc8c848 | 511 | |
676385e2 PH |
512 | * GLR parsing |
513 | The declaration | |
514 | %glr-parser | |
515 | causes Bison to produce a Generalized LR (GLR) parser, capable of handling | |
516 | almost any context-free grammar, ambiguous or not. The new declarations | |
e8832397 | 517 | %dprec and %merge on grammar rules allow parse-time resolution of |
676385e2 PH |
518 | ambiguities. Contributed by Paul Hilfinger. |
519 | ||
7933f2b5 | 520 | Unfortunately Bison 1.50 does not work properly on 64-bit hosts |
420f93c8 PE |
521 | like the Alpha, so please stick to 32-bit hosts for now. |
522 | ||
8c165d89 AD |
523 | * Output Directory |
524 | When not in Yacc compatibility mode, when the output file was not | |
e88dbdbf | 525 | specified, running `bison foo/bar.y' created `foo/bar.c'. It |
8c165d89 AD |
526 | now creates `bar.c'. |
527 | ||
007a50a4 AD |
528 | * Undefined token |
529 | The undefined token was systematically mapped to 2 which prevented | |
e88dbdbf | 530 | the use of 2 by the user. This is no longer the case. |
007a50a4 | 531 | |
77714df2 | 532 | * Unknown token numbers |
e88dbdbf | 533 | If yylex returned an out of range value, yyparse could die. This is |
007a50a4 AD |
534 | no longer the case. |
535 | ||
23c5a174 | 536 | * Error token |
e88dbdbf | 537 | According to POSIX, the error token must be 256. |
23c5a174 AD |
538 | Bison extends this requirement by making it a preference: *if* the |
539 | user specified that one of her tokens is numbered 256, then error | |
540 | will be mapped onto another number. | |
541 | ||
217598da | 542 | * Verbose error messages |
e88dbdbf | 543 | They no longer report `..., expecting error or...' for states where |
217598da AD |
544 | error recovery is possible. |
545 | ||
546 | * End token | |
547 | Defaults to `$end' instead of `$'. | |
548 | ||
68cd8af3 PE |
549 | * Error recovery now conforms to documentation and to POSIX |
550 | When a Bison-generated parser encounters a syntax error, it now pops | |
551 | the stack until it finds a state that allows shifting the error | |
552 | token. Formerly, it popped the stack until it found a state that | |
553 | allowed some non-error action other than a default reduction on the | |
554 | error token. The new behavior has long been the documented behavior, | |
555 | and has long been required by POSIX. For more details, please see | |
337116ba PE |
556 | Paul Eggert, "Reductions during Bison error handling" (2002-05-20) |
557 | <http://lists.gnu.org/archive/html/bug-bison/2002-05/msg00038.html>. | |
68cd8af3 | 558 | |
5504898e AD |
559 | * Traces |
560 | Popped tokens and nonterminals are now reported. | |
561 | ||
a861a339 PE |
562 | * Larger grammars |
563 | Larger grammars are now supported (larger token numbers, larger grammar | |
564 | size (= sum of the LHS and RHS lengths), larger LALR tables). | |
565 | Formerly, many of these numbers ran afoul of 16-bit limits; | |
566 | now these limits are 32 bits on most hosts. | |
355e7c1c | 567 | |
77714df2 | 568 | * Explicit initial rule |
643a5994 AD |
569 | Bison used to play hacks with the initial rule, which the user does |
570 | not write. It is now explicit, and visible in the reports and | |
571 | graphs as rule 0. | |
23c5a174 | 572 | |
77714df2 | 573 | * Useless rules |
643a5994 | 574 | Before, Bison reported the useless rules, but, although not used, |
77714df2 | 575 | included them in the parsers. They are now actually removed. |
23c5a174 | 576 | |
6b98e4b5 AD |
577 | * Useless rules, useless nonterminals |
578 | They are now reported, as a warning, with their locations. | |
579 | ||
e8832397 AD |
580 | * Rules never reduced |
581 | Rules that can never be reduced because of conflicts are now | |
582 | reported. | |
583 | ||
77714df2 | 584 | * Incorrect `Token not used' |
11652ab3 AD |
585 | On a grammar such as |
586 | ||
587 | %token useless useful | |
588 | %% | |
589 | exp: '0' %prec useful; | |
590 | ||
591 | where a token was used to set the precedence of the last rule, | |
592 | bison reported both `useful' and `useless' as useless tokens. | |
593 | ||
77714df2 AD |
594 | * Revert the C++ namespace changes introduced in 1.31 |
595 | as they caused too many portability hassles. | |
0179dd65 | 596 | |
b2d52318 AD |
597 | * Default locations |
598 | By an accident of design, the default computation of @$ was | |
599 | performed after another default computation was performed: @$ = @1. | |
600 | The latter is now removed: YYLLOC_DEFAULT is fully responsible of | |
601 | the computation of @$. | |
adc8c848 | 602 | |
b7c49edf AD |
603 | * Token end-of-file |
604 | The token end of file may be specified by the user, in which case, | |
605 | the user symbol is used in the reports, the graphs, and the verbose | |
a861a339 | 606 | error messages instead of `$end', which remains being the default. |
b7c49edf | 607 | For instance |
7bd6c77e | 608 | %token MYEOF 0 |
b7c49edf | 609 | or |
7bd6c77e | 610 | %token MYEOF 0 "end of file" |
fdbcd8e2 AD |
611 | |
612 | * Semantic parser | |
613 | This old option, which has been broken for ages, is removed. | |
614 | ||
a861a339 PE |
615 | * New translations |
616 | Brazilian Portuguese, thanks to Alexandre Folle de Menezes. | |
84614e13 AD |
617 | Croatian, thanks to Denis Lackovic. |
618 | ||
77714df2 | 619 | * Incorrect token definitions |
e88dbdbf | 620 | When given `%token 'a' "A"', Bison used to output `#define 'a' 65'. |
b87f8b21 | 621 | |
77714df2 AD |
622 | * Token definitions as enums |
623 | Tokens are output both as the traditional #define's, and, provided | |
624 | the compiler supports ANSI C or is a C++ compiler, as enums. | |
e88dbdbf | 625 | This lets debuggers display names instead of integers. |
77714df2 | 626 | |
ec3bc396 AD |
627 | * Reports |
628 | In addition to --verbose, bison supports --report=THINGS, which | |
629 | produces additional information: | |
b408954b AD |
630 | - itemset |
631 | complete the core item sets with their closure | |
9e6e7ed2 PE |
632 | - lookahead [changed to `look-ahead' in 1.875e through 2.3, but changed back] |
633 | explicitly associate lookahead tokens to items | |
b408954b AD |
634 | - solved |
635 | describe shift/reduce conflicts solving. | |
636 | Bison used to systematically output this information on top of | |
637 | the report. Solved conflicts are now attached to their states. | |
ec3bc396 | 638 | |
9af3fbce AD |
639 | * Type clashes |
640 | Previous versions don't complain when there is a type clash on | |
641 | the default action if the rule has a mid-rule action, such as in: | |
642 | ||
643 | %type <foo> bar | |
644 | %% | |
645 | bar: '0' {} '0'; | |
646 | ||
647 | This is fixed. | |
a861a339 PE |
648 | |
649 | * GNU M4 is now required when using Bison. | |
f987e9d2 | 650 | \f |
76551463 AD |
651 | Changes in version 1.35, 2002-03-25: |
652 | ||
653 | * C Skeleton | |
654 | Some projects use Bison's C parser with C++ compilers, and define | |
655 | YYSTYPE as a class. The recent adjustment of C parsers for data | |
656 | alignment and 64 bit architectures made this impossible. | |
657 | ||
658 | Because for the time being no real solution for C++ parser | |
659 | generation exists, kludges were implemented in the parser to | |
660 | maintain this use. In the future, when Bison has C++ parsers, this | |
661 | kludge will be disabled. | |
662 | ||
663 | This kludge also addresses some C++ problems when the stack was | |
664 | extended. | |
76551463 AD |
665 | \f |
666 | Changes in version 1.34, 2002-03-12: | |
667 | ||
668 | * File name clashes are detected | |
669 | $ bison foo.y -d -o foo.x | |
670 | fatal error: header and parser would both be named `foo.x' | |
671 | ||
672 | * A missing `;' at the end of a rule triggers a warning | |
673 | In accordance with POSIX, and in agreement with other | |
674 | Yacc implementations, Bison will mandate this semicolon in the near | |
675 | future. This eases the implementation of a Bison parser of Bison | |
676 | grammars by making this grammar LALR(1) instead of LR(2). To | |
677 | facilitate the transition, this release introduces a warning. | |
678 | ||
679 | * Revert the C++ namespace changes introduced in 1.31, as they caused too | |
680 | many portability hassles. | |
681 | ||
682 | * DJGPP support added. | |
683 | ||
684 | * Fix test suite portability problems. | |
685 | \f | |
686 | Changes in version 1.33, 2002-02-07: | |
687 | ||
688 | * Fix C++ issues | |
689 | Groff could not be compiled for the definition of size_t was lacking | |
690 | under some conditions. | |
691 | ||
692 | * Catch invalid @n | |
693 | As is done with $n. | |
694 | \f | |
695 | Changes in version 1.32, 2002-01-23: | |
696 | ||
697 | * Fix Yacc output file names | |
698 | ||
699 | * Portability fixes | |
700 | ||
701 | * Italian, Dutch translations | |
702 | \f | |
52d1aeee MA |
703 | Changes in version 1.31, 2002-01-14: |
704 | ||
705 | * Many Bug Fixes | |
706 | ||
707 | * GNU Gettext and %expect | |
708 | GNU Gettext asserts 10 s/r conflicts, but there are 7. Now that | |
709 | Bison dies on incorrect %expectations, we fear there will be | |
710 | too many bug reports for Gettext, so _for the time being_, %expect | |
711 | does not trigger an error when the input file is named `plural.y'. | |
712 | ||
713 | * Use of alloca in parsers | |
714 | If YYSTACK_USE_ALLOCA is defined to 0, then the parsers will use | |
715 | malloc exclusively. Since 1.29, but was not NEWS'ed. | |
716 | ||
717 | alloca is used only when compiled with GCC, to avoid portability | |
718 | problems as on AIX. | |
719 | ||
b47dbebe PE |
720 | * yyparse now returns 2 if memory is exhausted; formerly it dumped core. |
721 | ||
52d1aeee MA |
722 | * When the generated parser lacks debugging code, YYDEBUG is now 0 |
723 | (as POSIX requires) instead of being undefined. | |
724 | ||
725 | * User Actions | |
726 | Bison has always permitted actions such as { $$ = $1 }: it adds the | |
727 | ending semicolon. Now if in Yacc compatibility mode, the semicolon | |
728 | is no longer output: one has to write { $$ = $1; }. | |
729 | ||
730 | * Better C++ compliance | |
731 | The output parsers try to respect C++ namespaces. | |
76551463 | 732 | [This turned out to be a failed experiment, and it was reverted later.] |
52d1aeee MA |
733 | |
734 | * Reduced Grammars | |
735 | Fixed bugs when reporting useless nonterminals. | |
736 | ||
737 | * 64 bit hosts | |
738 | The parsers work properly on 64 bit hosts. | |
739 | ||
740 | * Error messages | |
741 | Some calls to strerror resulted in scrambled or missing error messages. | |
742 | ||
743 | * %expect | |
744 | When the number of shift/reduce conflicts is correct, don't issue | |
745 | any warning. | |
746 | ||
747 | * The verbose report includes the rule line numbers. | |
748 | ||
749 | * Rule line numbers are fixed in traces. | |
750 | ||
751 | * Swedish translation | |
752 | ||
753 | * Parse errors | |
754 | Verbose parse error messages from the parsers are better looking. | |
755 | Before: parse error: unexpected `'/'', expecting `"number"' or `'-'' or `'('' | |
756 | Now: parse error: unexpected '/', expecting "number" or '-' or '(' | |
757 | ||
758 | * Fixed parser memory leaks. | |
759 | When the generated parser was using malloc to extend its stacks, the | |
760 | previous allocations were not freed. | |
761 | ||
762 | * Fixed verbose output file. | |
763 | Some newlines were missing. | |
764 | Some conflicts in state descriptions were missing. | |
765 | ||
766 | * Fixed conflict report. | |
767 | Option -v was needed to get the result. | |
768 | ||
769 | * %expect | |
770 | Was not used. | |
771 | Mismatches are errors, not warnings. | |
772 | ||
773 | * Fixed incorrect processing of some invalid input. | |
774 | ||
775 | * Fixed CPP guards: 9foo.h uses BISON_9FOO_H instead of 9FOO_H. | |
776 | ||
777 | * Fixed some typos in the documentation. | |
778 | ||
779 | * %token MY_EOF 0 is supported. | |
780 | Before, MY_EOF was silently renumbered as 257. | |
781 | ||
782 | * doc/refcard.tex is updated. | |
783 | ||
784 | * %output, %file-prefix, %name-prefix. | |
785 | New. | |
786 | ||
787 | * --output | |
788 | New, aliasing `--output-file'. | |
789 | \f | |
76551463 | 790 | Changes in version 1.30, 2001-10-26: |
342b8b6e | 791 | |
fdac0091 PE |
792 | * `--defines' and `--graph' have now an optional argument which is the |
793 | output file name. `-d' and `-g' do not change; they do not take any | |
342b8b6e AD |
794 | argument. |
795 | ||
796 | * `%source_extension' and `%header_extension' are removed, failed | |
797 | experiment. | |
798 | ||
f987e9d2 AD |
799 | * Portability fixes. |
800 | \f | |
9f4503d6 | 801 | Changes in version 1.29, 2001-09-07: |
342b8b6e AD |
802 | |
803 | * The output file does not define const, as this caused problems when used | |
804 | with common autoconfiguration schemes. If you still use ancient compilers | |
805 | that lack const, compile with the equivalent of the C compiler option | |
806 | `-Dconst='. autoconf's AC_C_CONST macro provides one way to do this. | |
807 | ||
808 | * Added `-g' and `--graph'. | |
f87a2205 | 809 | |
f2b5126e PB |
810 | * The Bison manual is now distributed under the terms of the GNU FDL. |
811 | ||
f1c63ced | 812 | * The input and the output files has automatically a similar extension. |
234a3be3 | 813 | |
f87a2205 JT |
814 | * Russian translation added. |
815 | ||
816 | * NLS support updated; should hopefully be less troublesome. | |
817 | ||
818 | * Added the old Bison reference card. | |
c33638bb AD |
819 | |
820 | * Added `--locations' and `%locations'. | |
6deb4447 | 821 | |
cd5bd6ac AD |
822 | * Added `-S' and `--skeleton'. |
823 | ||
62ab6972 AD |
824 | * `%raw', `-r', `--raw' is disabled. |
825 | ||
cd5bd6ac AD |
826 | * Special characters are escaped when output. This solves the problems |
827 | of the #line lines with path names including backslashes. | |
828 | ||
6deb4447 | 829 | * New directives. |
4ecbf796 MA |
830 | `%yacc', `%fixed_output_files', `%defines', `%no_parser', `%verbose', |
831 | `%debug', `%source_extension' and `%header_extension'. | |
f987e9d2 AD |
832 | |
833 | * @$ | |
834 | Automatic location tracking. | |
f87a2205 | 835 | \f |
9f4503d6 | 836 | Changes in version 1.28, 1999-07-06: |
d2e00347 JT |
837 | |
838 | * Should compile better now with K&R compilers. | |
839 | ||
840 | * Added NLS. | |
841 | ||
842 | * Fixed a problem with escaping the double quote character. | |
843 | ||
844 | * There is now a FAQ. | |
845 | \f | |
5c31c3c2 JT |
846 | Changes in version 1.27: |
847 | ||
848 | * The make rule which prevented bison.simple from being created on | |
849 | some systems has been fixed. | |
850 | \f | |
851 | Changes in version 1.26: | |
4be07551 JT |
852 | |
853 | * Bison now uses automake. | |
854 | ||
855 | * New mailing lists: <bug-bison@gnu.org> and <help-bison@gnu.org>. | |
856 | ||
857 | * Token numbers now start at 257 as previously documented, not 258. | |
858 | ||
859 | * Bison honors the TMPDIR environment variable. | |
860 | ||
861 | * A couple of buffer overruns have been fixed. | |
f51dbca1 JT |
862 | |
863 | * Problems when closing files should now be reported. | |
864 | ||
865 | * Generated parsers should now work even on operating systems which do | |
866 | not provide alloca(). | |
4be07551 | 867 | \f |
9f4503d6 | 868 | Changes in version 1.25, 1995-10-16: |
df8878c5 RS |
869 | |
870 | * Errors in the input grammar are not fatal; Bison keeps reading | |
871 | the grammar file, and reports all the errors found in it. | |
8c44d3ec | 872 | |
df8878c5 RS |
873 | * Tokens can now be specified as multiple-character strings: for |
874 | example, you could use "<=" for a token which looks like <=, instead | |
875 | of chosing a name like LESSEQ. | |
876 | ||
877 | * The %token_table declaration says to write a table of tokens (names | |
878 | and numbers) into the parser file. The yylex function can use this | |
879 | table to recognize multiple-character string tokens, or for other | |
880 | purposes. | |
881 | ||
882 | * The %no_lines declaration says not to generate any #line preprocessor | |
883 | directives in the parser file. | |
884 | ||
885 | * The %raw declaration says to use internal Bison token numbers, not | |
886 | Yacc-compatible token numbers, when token names are defined as macros. | |
887 | ||
888 | * The --no-parser option produces the parser tables without including | |
889 | the parser engine; a project can now use its own parser engine. | |
890 | The actions go into a separate file called NAME.act, in the form of | |
891 | a switch statement body. | |
892 | \f | |
6780ca7a DM |
893 | Changes in version 1.23: |
894 | ||
4d019228 DM |
895 | The user can define YYPARSE_PARAM as the name of an argument to be |
896 | passed into yyparse. The argument should have type void *. It should | |
897 | actually point to an object. Grammar actions can access the variable | |
898 | by casting it to the proper pointer type. | |
6780ca7a | 899 | |
6780ca7a | 900 | Line numbers in output file corrected. |
6780ca7a DM |
901 | \f |
902 | Changes in version 1.22: | |
903 | ||
904 | --help option added. | |
6780ca7a DM |
905 | \f |
906 | Changes in version 1.20: | |
907 | ||
908 | Output file does not redefine const for C++. | |
9f4503d6 AD |
909 | |
910 | Local Variables: | |
911 | mode: outline | |
912 | End: | |
76551463 AD |
913 | |
914 | ----- | |
915 | ||
d6ca7905 | 916 | Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, |
279cabb6 | 917 | 2004, 2005, 2006, 2007 Free Software Foundation, Inc. |
76551463 | 918 | |
75eb3bc4 | 919 | This file is part of Bison, the GNU Compiler Compiler. |
76551463 | 920 | |
75eb3bc4 | 921 | Bison is free software; you can redistribute it and/or modify |
76551463 AD |
922 | it under the terms of the GNU General Public License as published by |
923 | the Free Software Foundation; either version 2, or (at your option) | |
924 | any later version. | |
925 | ||
75eb3bc4 | 926 | Bison is distributed in the hope that it will be useful, |
76551463 AD |
927 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
928 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
929 | GNU General Public License for more details. | |
930 | ||
931 | You should have received a copy of the GNU General Public License | |
932 | along with autoconf; see the file COPYING. If not, write to | |
0fb669f9 PE |
933 | the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, |
934 | Boston, MA 02110-1301, USA. |