Commit | Line | Data |
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416bd7a9 MA |
1 | -*- outline -*- |
2 | ||
efea6231 AD |
3 | * URGENT: Documenting C++ output |
4 | Write a first documentation for C++ output. | |
5 | ||
3ae2b51f AD |
6 | * value_components_used |
7 | Was defined but not used: where was it coming from? It can't be to | |
8 | check if %union is used, since the user is free to $<foo>n on her | |
9 | union, doesn't she? | |
10 | ||
efea6231 AD |
11 | * yyerror, yyprint interface |
12 | It should be improved, in particular when using Bison features such as | |
13 | locations, and YYPARSE_PARAMS. For the time being, it is recommended | |
14 | to #define yyerror and yyprint to steal internal variables... | |
15 | ||
ec3bc396 | 16 | * documentation |
efea6231 | 17 | Explain $axiom (and maybe change its name: BTYacc names it `goal', |
d7215705 AD |
18 | byacc `$accept' probably based on AT&T Yacc, Meta `Start'...). |
19 | Complete the glossary (item, axiom, ?). | |
ec3bc396 | 20 | |
d7215705 AD |
21 | * Error messages |
22 | Some are really funky. For instance | |
23 | ||
24 | type clash (`%s' `%s') on default action | |
25 | ||
26 | is really weird. Revisit them all. | |
27 | ||
28 | * Report documentation | |
ec3bc396 AD |
29 | Extend with error. The hard part will probably be finding the right |
30 | rule so that a single state does not exhibit to many yet undocumented | |
31 | ``features''. Maybe an empty action ought to be presented too. Shall | |
32 | we try to make a single grammar with all these features, or should we | |
33 | have several very small grammars? | |
34 | ||
d7215705 | 35 | * Documentation |
ec3bc396 AD |
36 | Some history of Bison and some bibliography would be most welcome. |
37 | Are there any Texinfo standards for bibliography? | |
38 | ||
6cbfbcc5 AD |
39 | * Several %unions |
40 | I think this is a pleasant (but useless currently) feature, but in the | |
41 | future, I want a means to %include other bits of grammars, and _then_ | |
42 | it will be important for the various bits to define their needs in | |
43 | %union. | |
76551463 | 44 | |
5c0a0514 AD |
45 | When implementing multiple-%union support, bare the following in mind: |
46 | ||
47 | - when --yacc, this must be flagged as an error. Don't make it fatal | |
48 | though. | |
49 | ||
50 | - The #line must now appear *inside* the definition of yystype. | |
51 | Something like | |
52 | ||
53 | { | |
54 | #line 12 "foo.y" | |
55 | int ival; | |
56 | #line 23 "foo.y" | |
57 | char *sval; | |
58 | } | |
59 | ||
ec3bc396 AD |
60 | * --report=conflict-path |
61 | Provide better assistance for understanding the conflicts by providing | |
d7215705 AD |
62 | a sample text exhibiting the (LALR) ambiguity. See the paper from |
63 | DeRemer and Penello: they already provide the algorithm. | |
308a2f76 | 64 | |
eaff5ee3 | 65 | * Coding system independence |
4358321a | 66 | Paul notes: |
eaff5ee3 AD |
67 | |
68 | Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is | |
69 | 255). It also assumes that the 8-bit character encoding is | |
70 | the same for the invocation of 'bison' as it is for the | |
71 | invocation of 'cc', but this is not necessarily true when | |
72 | people run bison on an ASCII host and then use cc on an EBCDIC | |
73 | host. I don't think these topics are worth our time | |
74 | addressing (unless we find a gung-ho volunteer for EBCDIC or | |
75 | PDP-10 ports :-) but they should probably be documented | |
76 | somewhere. | |
77 | ||
8b3ba7ff AD |
78 | * Output directory |
79 | Akim: | |
80 | ||
81 | | I consider this to be a bug in bison: | |
82 | | | |
83 | | /tmp % mkdir src | |
84 | | /tmp % cp ~/src/bison/tests/calc.y src | |
85 | | /tmp % mkdir build && cd build | |
86 | | /tmp/build % bison ../src/calc.y | |
87 | | /tmp/build % cd .. | |
88 | | /tmp % ls -l build src | |
89 | | build: | |
90 | | total 0 | |
91 | | | |
92 | | src: | |
93 | | total 32 | |
94 | | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c | |
95 | | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y | |
96 | | | |
97 | | | |
98 | | Would it be safe to change this behavior to something more reasonable? | |
99 | | Do you think some people depend upon this? | |
100 | ||
101 | Jim: | |
102 | ||
103 | Is it that behavior documented? | |
104 | If so, then it's probably not reasonable to change it. | |
105 | I've Cc'd the automake list, because some of automake's | |
106 | rules use bison through $(YACC) -- though I'll bet they | |
107 | all use it in yacc-compatible mode. | |
108 | ||
109 | Pavel: | |
110 | ||
111 | Hello, Jim and others! | |
112 | ||
113 | > Is it that behavior documented? | |
114 | > If so, then it's probably not reasonable to change it. | |
115 | > I've Cc'd the automake list, because some of automake's | |
116 | > rules use bison through $(YACC) -- though I'll bet they | |
117 | > all use it in yacc-compatible mode. | |
118 | ||
119 | Yes, Automake currently used bison in Automake-compatible mode, but it | |
120 | would be fair for Automake to switch to the native mode as long as the | |
121 | processed files are distributed and "missing" emulates bison. | |
122 | ||
123 | In any case, the makefiles should specify the output file explicitly | |
124 | instead of relying on weird defaults. | |
125 | ||
126 | > | src: | |
127 | > | total 32 | |
128 | > | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c | |
129 | > | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y | |
130 | ||
131 | This is not _that_ ugly as it seems - with Automake you want to put | |
132 | sources where they belong - to the source directory. | |
133 | ||
134 | > | This is not _that_ ugly as it seems - with Automake you want to put | |
135 | > | sources where they belong - to the source directory. | |
136 | > | |
137 | > The difference source/build you are referring to is based on Automake | |
138 | > concepts. They have no sense at all for tools such as bison or gcc | |
139 | > etc. They have input and output. I do not want them to try to grasp | |
140 | > source/build. I want them to behave uniformly: output *here*. | |
141 | ||
142 | I realize that. | |
143 | ||
144 | It's unfortunate that the native mode of Bison behaves in a less uniform | |
145 | way than the yacc mode. I agree with your point. Bison maintainters may | |
146 | want to fix it along with the documentation. | |
147 | ||
148 | ||
fa770c86 AD |
149 | * Unit rules |
150 | Maybe we could expand unit rules, i.e., transform | |
151 | ||
152 | exp: arith | bool; | |
153 | arith: exp '+' exp; | |
154 | bool: exp '&' exp; | |
155 | ||
156 | into | |
157 | ||
158 | exp: exp '+' exp | exp '&' exp; | |
159 | ||
160 | when there are no actions. This can significantly speed up some | |
d7215705 AD |
161 | grammars. I can't find the papers. In particular the book `LR |
162 | parsing: Theory and Practice' is impossible to find, but according to | |
163 | `Parsing Techniques: a Practical Guide', it includes information about | |
164 | this issue. Does anybody have it? | |
fa770c86 | 165 | |
51dec47b AD |
166 | * Stupid error messages |
167 | An example shows it easily: | |
168 | ||
169 | src/bison/tests % ./testsuite -k calc,location,error-verbose -l | |
170 | GNU Bison 1.49a test suite test groups: | |
171 | ||
172 | NUM: FILENAME:LINE TEST-GROUP-NAME | |
173 | KEYWORDS | |
174 | ||
175 | 51: calc.at:440 Calculator --locations --yyerror-verbose | |
176 | 52: calc.at:442 Calculator --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose | |
177 | 54: calc.at:445 Calculator --debug --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose | |
178 | src/bison/tests % ./testsuite 51 -d | |
179 | ## --------------------------- ## | |
180 | ## GNU Bison 1.49a test suite. ## | |
181 | ## --------------------------- ## | |
182 | 51: calc.at:440 ok | |
183 | ## ---------------------------- ## | |
184 | ## All 1 tests were successful. ## | |
185 | ## ---------------------------- ## | |
186 | src/bison/tests % cd ./testsuite.dir/51 | |
187 | tests/testsuite.dir/51 % echo "()" | ./calc | |
188 | 1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '(' | |
fa770c86 AD |
189 | |
190 | * read_pipe.c | |
191 | This is not portable to DOS for instance. Implement a more portable | |
192 | scheme. Sources of inspiration include GNU diff, and Free Recode. | |
193 | ||
aef1ffd5 AD |
194 | * Memory leaks in the generator |
195 | A round of memory leak clean ups would be most welcome. Dmalloc, | |
196 | Checker GCC, Electric Fence, or Valgrind: you chose your tool. | |
197 | ||
198 | * Memory leaks in the parser | |
199 | The same applies to the generated parsers. In particular, this is | |
200 | critical for user data: when aborting a parsing, when handling the | |
201 | error token etc., we often throw away yylval without giving a chance | |
202 | of cleaning it up to the user. | |
203 | ||
bcb05e75 MA |
204 | * --graph |
205 | Show reductions. [] | |
206 | ||
704a47c4 | 207 | * Broken options ? |
c3995d99 | 208 | ** %no-lines [ok] |
04a76783 | 209 | ** %no-parser [] |
fbbf9b3b | 210 | ** %pure-parser [] |
04a76783 MA |
211 | ** %token-table [] |
212 | ** Options which could use parse_dquoted_param (). | |
213 | Maybe transfered in lex.c. | |
214 | *** %skeleton [ok] | |
215 | *** %output [] | |
216 | *** %file-prefix [] | |
217 | *** %name-prefix [] | |
ec93a213 | 218 | |
fbbf9b3b | 219 | ** Skeleton strategy. [] |
c3a8cbaa MA |
220 | Must we keep %no-parser? |
221 | %token-table? | |
fbbf9b3b | 222 | *** New skeletons. [] |
416bd7a9 | 223 | |
c111e171 | 224 | * src/print_graph.c |
31b53af2 | 225 | Find the best graph parameters. [] |
63c2d5de MA |
226 | |
227 | * doc/bison.texinfo | |
1a4648ff | 228 | ** Update |
c3a8cbaa | 229 | informations about ERROR_VERBOSE. [] |
1a4648ff | 230 | ** Add explainations about |
c3a8cbaa MA |
231 | skeleton muscles. [] |
232 | %skeleton. [] | |
eeeb962b | 233 | |
704a47c4 | 234 | * testsuite |
c3a8cbaa MA |
235 | ** tests/pure-parser.at [] |
236 | New tests. | |
0f8d586a AD |
237 | |
238 | * Debugging parsers | |
239 | ||
240 | From Greg McGary: | |
241 | ||
242 | akim demaille <akim.demaille@epita.fr> writes: | |
243 | ||
244 | > With great pleasure! Nonetheless, things which are debatable | |
245 | > (or not, but just `big') should be discuss in `public': something | |
246 | > like help- or bug-bison@gnu.org is just fine. Jesse and I are there, | |
247 | > but there is also Jim and some other people. | |
248 | ||
249 | I have no idea whether it qualifies as big or controversial, so I'll | |
250 | just summarize for you. I proposed this change years ago and was | |
251 | surprised that it was met with utter indifference! | |
252 | ||
253 | This debug feature is for the programs/grammars one develops with | |
254 | bison, not for debugging bison itself. I find that the YYDEBUG | |
255 | output comes in a very inconvenient format for my purposes. | |
256 | When debugging gcc, for instance, what I want is to see a trace of | |
257 | the sequence of reductions and the line#s for the semantic actions | |
258 | so I can follow what's happening. Single-step in gdb doesn't cut it | |
259 | because to move from one semantic action to the next takes you through | |
260 | lots of internal machinery of the parser, which is uninteresting. | |
261 | ||
262 | The change I made was to the format of the debug output, so that it | |
263 | comes out in the format of C error messages, digestible by emacs | |
264 | compile mode, like so: | |
265 | ||
266 | grammar.y:1234: foo: bar(0x123456) baz(0x345678) | |
267 | ||
268 | where "foo: bar baz" is the reduction rule, whose semantic action | |
269 | appears on line 1234 of the bison grammar file grammar.y. The hex | |
270 | numbers on the rhs tokens are the parse-stack values associated with | |
271 | those tokens. Of course, yytype might be something totally | |
272 | incompatible with that representation, but for the most part, yytype | |
273 | values are single words (scalars or pointers). In the case of gcc, | |
274 | they're most often pointers to tree nodes. Come to think of it, the | |
275 | right thing to do is to make the printing of stack values be | |
276 | user-definable. It would also be useful to include the filename & | |
277 | line# of the file being parsed, but the main filename & line# should | |
278 | continue to be that of grammar.y | |
279 | ||
280 | Anyway, this feature has saved my life on numerous occasions. The way | |
281 | I customarily use it is to first run bison with the traces on, isolate | |
282 | the sequence of reductions that interests me, put those traces in a | |
283 | buffer and force it into compile-mode, then visit each of those lines | |
284 | in the grammar and set breakpoints with C-x SPACE. Then, I can run | |
285 | again under the control of gdb and stop at each semantic action. | |
286 | With the hex addresses of tree nodes, I can inspect the values | |
287 | associated with any rhs token. | |
288 | ||
289 | You like? | |
cd6a695e AD |
290 | |
291 | * input synclines | |
292 | Some users create their foo.y files, and equip them with #line. Bison | |
293 | should recognize these, and preserve them. | |
0e95c1dd AD |
294 | |
295 | * BTYacc | |
296 | See if we can integrate backtracking in Bison. Contact the BTYacc | |
297 | maintainers. | |
298 | ||
0e95c1dd AD |
299 | * RR conflicts |
300 | See if we can use precedence between rules to solve RR conflicts. See | |
301 | what POSIX says. | |
302 | ||
303 | * Precedence | |
304 | It is unfortunate that there is a total order for precedence. It | |
305 | makes it impossible to have modular precedence information. We should | |
306 | move to partial orders. | |
307 | ||
3c9160d9 AD |
308 | This will be possible with a Bison parser for the grammar, as it will |
309 | make it much easier to extend the grammar. | |
310 | ||
0e95c1dd | 311 | * Parsing grammars |
3c9160d9 | 312 | Rewrite the reader in Flex/Bison. There will be delicate parts, in |
9306c70c AD |
313 | particular, expect the scanner to be hard to write. Many interesting |
314 | features cannot be implemented without such a new reader. | |
f294a2c2 | 315 | |
d7215705 AD |
316 | I'm on it! I already have a proto that parses (but the actions are |
317 | not fully written yet). -- Akim | |
318 | ||
69991a58 AD |
319 | * $undefined |
320 | From Hans: | |
321 | - If the Bison generated parser experiences an undefined number in the | |
322 | character range, that character is written out in diagnostic messages, an | |
323 | addition to the $undefined value. | |
324 | ||
325 | Suggest: Change the name $undefined to undefined; looks better in outputs. | |
326 | ||
327 | * Default Action | |
328 | From Hans: | |
329 | - For use with my C++ parser, I transported the "switch (yyn)" statement | |
330 | that Bison writes to the bison.simple skeleton file. This way, I can remove | |
331 | the current default rule $$ = $1 implementation, which causes a double | |
332 | assignment to $$ which may not be OK under C++, replacing it with a | |
333 | "default:" part within the switch statement. | |
334 | ||
335 | Note that the default rule $$ = $1, when typed, is perfectly OK under C, | |
336 | but in the C++ implementation I made, this rule is different from | |
337 | $<type_name>$ = $<type_name>1. I therefore think that one should implement | |
338 | a Bison option where every typed default rule is explicitly written out | |
339 | (same typed ruled can of course be grouped together). | |
340 | ||
3c9160d9 AD |
341 | Note: Robert Anisko handles this. He knows how to do it. |
342 | ||
0164db68 AD |
343 | * Warnings |
344 | It would be nice to have warning support. See how Autoconf handles | |
345 | them, it is fairly well described there. It would be very nice to | |
346 | implement this in such a way that other programs could use | |
347 | lib/warnings.[ch]. | |
348 | ||
9306c70c AD |
349 | Don't work on this without first announcing you do, as I already have |
350 | thought about it, and know many of the components that can be used to | |
351 | implement it. | |
352 | ||
69991a58 AD |
353 | * Pre and post actions. |
354 | From: Florian Krohm <florian@edamail.fishkill.ibm.com> | |
355 | Subject: YYACT_EPILOGUE | |
356 | To: bug-bison@gnu.org | |
357 | X-Sent: 1 week, 4 days, 14 hours, 38 minutes, 11 seconds ago | |
358 | ||
359 | The other day I had the need for explicitly building the parse tree. I | |
360 | used %locations for that and defined YYLLOC_DEFAULT to call a function | |
361 | that returns the tree node for the production. Easy. But I also needed | |
362 | to assign the S-attribute to the tree node. That cannot be done in | |
363 | YYLLOC_DEFAULT, because it is invoked before the action is executed. | |
364 | The way I solved this was to define a macro YYACT_EPILOGUE that would | |
365 | be invoked after the action. For reasons of symmetry I also added | |
366 | YYACT_PROLOGUE. Although I had no use for that I can envision how it | |
367 | might come in handy for debugging purposes. | |
76551463 | 368 | All is needed is to add |
69991a58 AD |
369 | |
370 | #if YYLSP_NEEDED | |
371 | YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen, yyloc, (yylsp - yylen)); | |
372 | #else | |
373 | YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen); | |
374 | #endif | |
375 | ||
376 | at the proper place to bison.simple. Ditto for YYACT_PROLOGUE. | |
377 | ||
378 | I was wondering what you think about adding YYACT_PROLOGUE/EPILOGUE | |
379 | to bison. If you're interested, I'll work on a patch. | |
380 | ||
d7215705 AD |
381 | * Move to Graphviz |
382 | Well, VCG seems really dead. Move to Graphviz instead. Also, equip | |
383 | the parser with a means to create the (visual) parse tree. | |
384 | ||
f294a2c2 AD |
385 | ----- |
386 | ||
387 | Copyright (C) 2001, 2002 Free Software Foundation, Inc. | |
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