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Commit | Line | Data |
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416bd7a9 MA |
1 | -*- outline -*- |
2 | ||
6cbfbcc5 AD |
3 | * Several %unions |
4 | I think this is a pleasant (but useless currently) feature, but in the | |
5 | future, I want a means to %include other bits of grammars, and _then_ | |
6 | it will be important for the various bits to define their needs in | |
7 | %union. | |
76551463 | 8 | |
5c0a0514 AD |
9 | When implementing multiple-%union support, bare the following in mind: |
10 | ||
11 | - when --yacc, this must be flagged as an error. Don't make it fatal | |
12 | though. | |
13 | ||
14 | - The #line must now appear *inside* the definition of yystype. | |
15 | Something like | |
16 | ||
17 | { | |
18 | #line 12 "foo.y" | |
19 | int ival; | |
20 | #line 23 "foo.y" | |
21 | char *sval; | |
22 | } | |
23 | ||
eaff5ee3 | 24 | * Coding system independence |
4358321a | 25 | Paul notes: |
eaff5ee3 AD |
26 | |
27 | Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is | |
28 | 255). It also assumes that the 8-bit character encoding is | |
29 | the same for the invocation of 'bison' as it is for the | |
30 | invocation of 'cc', but this is not necessarily true when | |
31 | people run bison on an ASCII host and then use cc on an EBCDIC | |
32 | host. I don't think these topics are worth our time | |
33 | addressing (unless we find a gung-ho volunteer for EBCDIC or | |
34 | PDP-10 ports :-) but they should probably be documented | |
35 | somewhere. | |
36 | ||
8b3ba7ff AD |
37 | * Output directory |
38 | Akim: | |
39 | ||
40 | | I consider this to be a bug in bison: | |
41 | | | |
42 | | /tmp % mkdir src | |
43 | | /tmp % cp ~/src/bison/tests/calc.y src | |
44 | | /tmp % mkdir build && cd build | |
45 | | /tmp/build % bison ../src/calc.y | |
46 | | /tmp/build % cd .. | |
47 | | /tmp % ls -l build src | |
48 | | build: | |
49 | | total 0 | |
50 | | | |
51 | | src: | |
52 | | total 32 | |
53 | | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c | |
54 | | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y | |
55 | | | |
56 | | | |
57 | | Would it be safe to change this behavior to something more reasonable? | |
58 | | Do you think some people depend upon this? | |
59 | ||
60 | Jim: | |
61 | ||
62 | Is it that behavior documented? | |
63 | If so, then it's probably not reasonable to change it. | |
64 | I've Cc'd the automake list, because some of automake's | |
65 | rules use bison through $(YACC) -- though I'll bet they | |
66 | all use it in yacc-compatible mode. | |
67 | ||
68 | Pavel: | |
69 | ||
70 | Hello, Jim and others! | |
71 | ||
72 | > Is it that behavior documented? | |
73 | > If so, then it's probably not reasonable to change it. | |
74 | > I've Cc'd the automake list, because some of automake's | |
75 | > rules use bison through $(YACC) -- though I'll bet they | |
76 | > all use it in yacc-compatible mode. | |
77 | ||
78 | Yes, Automake currently used bison in Automake-compatible mode, but it | |
79 | would be fair for Automake to switch to the native mode as long as the | |
80 | processed files are distributed and "missing" emulates bison. | |
81 | ||
82 | In any case, the makefiles should specify the output file explicitly | |
83 | instead of relying on weird defaults. | |
84 | ||
85 | > | src: | |
86 | > | total 32 | |
87 | > | -rw-r--r-- 1 akim lrde 27553 oct 2 16:31 calc.tab.c | |
88 | > | -rw-r--r-- 1 akim lrde 3335 oct 2 16:31 calc.y | |
89 | ||
90 | This is not _that_ ugly as it seems - with Automake you want to put | |
91 | sources where they belong - to the source directory. | |
92 | ||
93 | > | This is not _that_ ugly as it seems - with Automake you want to put | |
94 | > | sources where they belong - to the source directory. | |
95 | > | |
96 | > The difference source/build you are referring to is based on Automake | |
97 | > concepts. They have no sense at all for tools such as bison or gcc | |
98 | > etc. They have input and output. I do not want them to try to grasp | |
99 | > source/build. I want them to behave uniformly: output *here*. | |
100 | ||
101 | I realize that. | |
102 | ||
103 | It's unfortunate that the native mode of Bison behaves in a less uniform | |
104 | way than the yacc mode. I agree with your point. Bison maintainters may | |
105 | want to fix it along with the documentation. | |
106 | ||
107 | ||
fa770c86 AD |
108 | * Unit rules |
109 | Maybe we could expand unit rules, i.e., transform | |
110 | ||
111 | exp: arith | bool; | |
112 | arith: exp '+' exp; | |
113 | bool: exp '&' exp; | |
114 | ||
115 | into | |
116 | ||
117 | exp: exp '+' exp | exp '&' exp; | |
118 | ||
119 | when there are no actions. This can significantly speed up some | |
120 | grammars. | |
121 | ||
51dec47b AD |
122 | * Stupid error messages |
123 | An example shows it easily: | |
124 | ||
125 | src/bison/tests % ./testsuite -k calc,location,error-verbose -l | |
126 | GNU Bison 1.49a test suite test groups: | |
127 | ||
128 | NUM: FILENAME:LINE TEST-GROUP-NAME | |
129 | KEYWORDS | |
130 | ||
131 | 51: calc.at:440 Calculator --locations --yyerror-verbose | |
132 | 52: calc.at:442 Calculator --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose | |
133 | 54: calc.at:445 Calculator --debug --defines --locations --name-prefix=calc --verbose --yacc --yyerror-verbose | |
134 | src/bison/tests % ./testsuite 51 -d | |
135 | ## --------------------------- ## | |
136 | ## GNU Bison 1.49a test suite. ## | |
137 | ## --------------------------- ## | |
138 | 51: calc.at:440 ok | |
139 | ## ---------------------------- ## | |
140 | ## All 1 tests were successful. ## | |
141 | ## ---------------------------- ## | |
142 | src/bison/tests % cd ./testsuite.dir/51 | |
143 | tests/testsuite.dir/51 % echo "()" | ./calc | |
144 | 1.2-1.3: parse error, unexpected ')', expecting error or "number" or '-' or '(' | |
fa770c86 | 145 | |
01c56de4 AD |
146 | * yyerror, yyprint interface |
147 | It should be improved, in particular when using Bison features such as | |
148 | locations, and YYPARSE_PARAMS. For the time being, it is recommended | |
149 | to #define yyerror and yyprint to steal internal variables... | |
150 | ||
fa770c86 AD |
151 | * read_pipe.c |
152 | This is not portable to DOS for instance. Implement a more portable | |
153 | scheme. Sources of inspiration include GNU diff, and Free Recode. | |
154 | ||
aef1ffd5 AD |
155 | * Memory leaks in the generator |
156 | A round of memory leak clean ups would be most welcome. Dmalloc, | |
157 | Checker GCC, Electric Fence, or Valgrind: you chose your tool. | |
158 | ||
159 | * Memory leaks in the parser | |
160 | The same applies to the generated parsers. In particular, this is | |
161 | critical for user data: when aborting a parsing, when handling the | |
162 | error token etc., we often throw away yylval without giving a chance | |
163 | of cleaning it up to the user. | |
164 | ||
bcb05e75 MA |
165 | * --graph |
166 | Show reductions. [] | |
167 | ||
704a47c4 | 168 | * Broken options ? |
c3995d99 | 169 | ** %no-lines [ok] |
04a76783 | 170 | ** %no-parser [] |
fbbf9b3b | 171 | ** %pure-parser [] |
04a76783 MA |
172 | ** %token-table [] |
173 | ** Options which could use parse_dquoted_param (). | |
174 | Maybe transfered in lex.c. | |
175 | *** %skeleton [ok] | |
176 | *** %output [] | |
177 | *** %file-prefix [] | |
178 | *** %name-prefix [] | |
ec93a213 | 179 | |
fbbf9b3b | 180 | ** Skeleton strategy. [] |
c3a8cbaa MA |
181 | Must we keep %no-parser? |
182 | %token-table? | |
fbbf9b3b | 183 | *** New skeletons. [] |
416bd7a9 | 184 | |
c111e171 | 185 | * src/print_graph.c |
31b53af2 | 186 | Find the best graph parameters. [] |
63c2d5de MA |
187 | |
188 | * doc/bison.texinfo | |
1a4648ff | 189 | ** Update |
c3a8cbaa | 190 | informations about ERROR_VERBOSE. [] |
1a4648ff | 191 | ** Add explainations about |
c3a8cbaa MA |
192 | skeleton muscles. [] |
193 | %skeleton. [] | |
eeeb962b | 194 | |
704a47c4 | 195 | * testsuite |
c3a8cbaa MA |
196 | ** tests/pure-parser.at [] |
197 | New tests. | |
0f8d586a AD |
198 | |
199 | * Debugging parsers | |
200 | ||
201 | From Greg McGary: | |
202 | ||
203 | akim demaille <akim.demaille@epita.fr> writes: | |
204 | ||
205 | > With great pleasure! Nonetheless, things which are debatable | |
206 | > (or not, but just `big') should be discuss in `public': something | |
207 | > like help- or bug-bison@gnu.org is just fine. Jesse and I are there, | |
208 | > but there is also Jim and some other people. | |
209 | ||
210 | I have no idea whether it qualifies as big or controversial, so I'll | |
211 | just summarize for you. I proposed this change years ago and was | |
212 | surprised that it was met with utter indifference! | |
213 | ||
214 | This debug feature is for the programs/grammars one develops with | |
215 | bison, not for debugging bison itself. I find that the YYDEBUG | |
216 | output comes in a very inconvenient format for my purposes. | |
217 | When debugging gcc, for instance, what I want is to see a trace of | |
218 | the sequence of reductions and the line#s for the semantic actions | |
219 | so I can follow what's happening. Single-step in gdb doesn't cut it | |
220 | because to move from one semantic action to the next takes you through | |
221 | lots of internal machinery of the parser, which is uninteresting. | |
222 | ||
223 | The change I made was to the format of the debug output, so that it | |
224 | comes out in the format of C error messages, digestible by emacs | |
225 | compile mode, like so: | |
226 | ||
227 | grammar.y:1234: foo: bar(0x123456) baz(0x345678) | |
228 | ||
229 | where "foo: bar baz" is the reduction rule, whose semantic action | |
230 | appears on line 1234 of the bison grammar file grammar.y. The hex | |
231 | numbers on the rhs tokens are the parse-stack values associated with | |
232 | those tokens. Of course, yytype might be something totally | |
233 | incompatible with that representation, but for the most part, yytype | |
234 | values are single words (scalars or pointers). In the case of gcc, | |
235 | they're most often pointers to tree nodes. Come to think of it, the | |
236 | right thing to do is to make the printing of stack values be | |
237 | user-definable. It would also be useful to include the filename & | |
238 | line# of the file being parsed, but the main filename & line# should | |
239 | continue to be that of grammar.y | |
240 | ||
241 | Anyway, this feature has saved my life on numerous occasions. The way | |
242 | I customarily use it is to first run bison with the traces on, isolate | |
243 | the sequence of reductions that interests me, put those traces in a | |
244 | buffer and force it into compile-mode, then visit each of those lines | |
245 | in the grammar and set breakpoints with C-x SPACE. Then, I can run | |
246 | again under the control of gdb and stop at each semantic action. | |
247 | With the hex addresses of tree nodes, I can inspect the values | |
248 | associated with any rhs token. | |
249 | ||
250 | You like? | |
cd6a695e AD |
251 | |
252 | * input synclines | |
253 | Some users create their foo.y files, and equip them with #line. Bison | |
254 | should recognize these, and preserve them. | |
0e95c1dd AD |
255 | |
256 | * BTYacc | |
257 | See if we can integrate backtracking in Bison. Contact the BTYacc | |
258 | maintainers. | |
259 | ||
260 | * Automaton report | |
261 | Display more clearly the lookaheads for each item. | |
262 | ||
263 | * RR conflicts | |
264 | See if we can use precedence between rules to solve RR conflicts. See | |
265 | what POSIX says. | |
266 | ||
267 | * Precedence | |
268 | It is unfortunate that there is a total order for precedence. It | |
269 | makes it impossible to have modular precedence information. We should | |
270 | move to partial orders. | |
271 | ||
3c9160d9 AD |
272 | This will be possible with a Bison parser for the grammar, as it will |
273 | make it much easier to extend the grammar. | |
274 | ||
0e95c1dd | 275 | * Parsing grammars |
3c9160d9 | 276 | Rewrite the reader in Flex/Bison. There will be delicate parts, in |
9306c70c AD |
277 | particular, expect the scanner to be hard to write. Many interesting |
278 | features cannot be implemented without such a new reader. | |
f294a2c2 | 279 | |
20c37f21 AD |
280 | * Presentation of the report file |
281 | From: "Baum, Nathan I" <s0009525@chelt.ac.uk> | |
282 | Subject: Token Alias Bug | |
283 | To: "'bug-bison@gnu.org'" <bug-bison@gnu.org> | |
284 | ||
285 | I've also noticed something, that whilst not *wrong*, is inconvienient: I | |
286 | use the verbose mode to help find the causes of unresolved shift/reduce | |
287 | conflicts. However, this mode insists on starting the .output file with a | |
288 | list of *resolved* conflicts, something I find quite useless. Might it be | |
289 | possible to define a -v mode, and a -vv mode -- Where the -vv mode shows | |
290 | everything, but the -v mode only tells you what you need for examining | |
291 | conflicts? (Or, perhaps, a "*** This state has N conflicts ***" marker above | |
292 | each state with conflicts.) | |
293 | ||
69991a58 AD |
294 | * $undefined |
295 | From Hans: | |
296 | - If the Bison generated parser experiences an undefined number in the | |
297 | character range, that character is written out in diagnostic messages, an | |
298 | addition to the $undefined value. | |
299 | ||
300 | Suggest: Change the name $undefined to undefined; looks better in outputs. | |
301 | ||
302 | * Default Action | |
303 | From Hans: | |
304 | - For use with my C++ parser, I transported the "switch (yyn)" statement | |
305 | that Bison writes to the bison.simple skeleton file. This way, I can remove | |
306 | the current default rule $$ = $1 implementation, which causes a double | |
307 | assignment to $$ which may not be OK under C++, replacing it with a | |
308 | "default:" part within the switch statement. | |
309 | ||
310 | Note that the default rule $$ = $1, when typed, is perfectly OK under C, | |
311 | but in the C++ implementation I made, this rule is different from | |
312 | $<type_name>$ = $<type_name>1. I therefore think that one should implement | |
313 | a Bison option where every typed default rule is explicitly written out | |
314 | (same typed ruled can of course be grouped together). | |
315 | ||
3c9160d9 AD |
316 | Note: Robert Anisko handles this. He knows how to do it. |
317 | ||
318 | * Documenting C++ output | |
319 | Write a first documentation for C++ output. | |
320 | ||
0164db68 AD |
321 | * Warnings |
322 | It would be nice to have warning support. See how Autoconf handles | |
323 | them, it is fairly well described there. It would be very nice to | |
324 | implement this in such a way that other programs could use | |
325 | lib/warnings.[ch]. | |
326 | ||
9306c70c AD |
327 | Don't work on this without first announcing you do, as I already have |
328 | thought about it, and know many of the components that can be used to | |
329 | implement it. | |
330 | ||
69991a58 AD |
331 | * Pre and post actions. |
332 | From: Florian Krohm <florian@edamail.fishkill.ibm.com> | |
333 | Subject: YYACT_EPILOGUE | |
334 | To: bug-bison@gnu.org | |
335 | X-Sent: 1 week, 4 days, 14 hours, 38 minutes, 11 seconds ago | |
336 | ||
337 | The other day I had the need for explicitly building the parse tree. I | |
338 | used %locations for that and defined YYLLOC_DEFAULT to call a function | |
339 | that returns the tree node for the production. Easy. But I also needed | |
340 | to assign the S-attribute to the tree node. That cannot be done in | |
341 | YYLLOC_DEFAULT, because it is invoked before the action is executed. | |
342 | The way I solved this was to define a macro YYACT_EPILOGUE that would | |
343 | be invoked after the action. For reasons of symmetry I also added | |
344 | YYACT_PROLOGUE. Although I had no use for that I can envision how it | |
345 | might come in handy for debugging purposes. | |
76551463 | 346 | All is needed is to add |
69991a58 AD |
347 | |
348 | #if YYLSP_NEEDED | |
349 | YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen, yyloc, (yylsp - yylen)); | |
350 | #else | |
351 | YYACT_EPILOGUE (yyval, (yyvsp - yylen), yylen); | |
352 | #endif | |
353 | ||
354 | at the proper place to bison.simple. Ditto for YYACT_PROLOGUE. | |
355 | ||
356 | I was wondering what you think about adding YYACT_PROLOGUE/EPILOGUE | |
357 | to bison. If you're interested, I'll work on a patch. | |
358 | ||
f294a2c2 AD |
359 | ----- |
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