-*- outline -*-
-* tokendefs
-This muscle should not exist: the information it contains should be
-available from the rest of bison. Once the information public, get
-rid of it.
+* Unit rules
+Maybe we could expand unit rules, i.e., transform
-* Broken options ?.
+ exp: arith | bool;
+ arith: exp '+' exp;
+ bool: exp '&' exp;
+
+into
+
+ exp: exp '+' exp | exp '&' exp;
+
+when there are no actions. This can significantly speed up some
+grammars.
+
+* Useless rules
+We have all the needed material to actually remove them. Do it.
+Or maybe not, but at least do not include them in the automaton.
+
+* read_pipe.c
+This is not portable to DOS for instance. Implement a more portable
+scheme. Sources of inspiration include GNU diff, and Free Recode.
+
+* NEWS
+Sort from 1.31 NEWS.
+
+* Prologue
+The %union is declared after the user C declarations. It can be
+a problem if YYSTYPE is declared after the user part. []
+
+Actually, the real problem seems that the %union ought to be output
+where it was defined. For instance, in gettext/intl/plural.y, we
+have:
+
+ %{
+ ...
+ #include "gettextP.h"
+ ...
+ %}
+
+ %union {
+ unsigned long int num;
+ enum operator op;
+ struct expression *exp;
+ }
+
+ %{
+ ...
+ static int yylex PARAMS ((YYSTYPE *lval, const char **pexp));
+ ...
+ %}
+
+Where the first part defines struct expression, the second uses it to
+define YYSTYPE, and the last uses YYSTYPE. Only this order is valid.
+
+* --graph
+Show reductions. []
+
+* Broken options ?
** %no-lines [ok]
** %no-parser []
** %pure-parser []
%token-table?
*** New skeletons. []
-* src/macrotab.[ch]
-Removing warnings when compiling. (gcc-warnings). [ok]
-
* src/print_graph.c
Find the best graph parameters. []
skeleton muscles. []
%skeleton. []
-* testsuite.
-** tests/reduce.at [ok]
+* testsuite
** tests/pure-parser.at []
New tests.
+
+* Debugging parsers
+
+From Greg McGary:
+
+akim demaille <akim.demaille@epita.fr> writes:
+
+> With great pleasure! Nonetheless, things which are debatable
+> (or not, but just `big') should be discuss in `public': something
+> like help- or bug-bison@gnu.org is just fine. Jesse and I are there,
+> but there is also Jim and some other people.
+
+I have no idea whether it qualifies as big or controversial, so I'll
+just summarize for you. I proposed this change years ago and was
+surprised that it was met with utter indifference!
+
+This debug feature is for the programs/grammars one develops with
+bison, not for debugging bison itself. I find that the YYDEBUG
+output comes in a very inconvenient format for my purposes.
+When debugging gcc, for instance, what I want is to see a trace of
+the sequence of reductions and the line#s for the semantic actions
+so I can follow what's happening. Single-step in gdb doesn't cut it
+because to move from one semantic action to the next takes you through
+lots of internal machinery of the parser, which is uninteresting.
+
+The change I made was to the format of the debug output, so that it
+comes out in the format of C error messages, digestible by emacs
+compile mode, like so:
+
+grammar.y:1234: foo: bar(0x123456) baz(0x345678)
+
+where "foo: bar baz" is the reduction rule, whose semantic action
+appears on line 1234 of the bison grammar file grammar.y. The hex
+numbers on the rhs tokens are the parse-stack values associated with
+those tokens. Of course, yytype might be something totally
+incompatible with that representation, but for the most part, yytype
+values are single words (scalars or pointers). In the case of gcc,
+they're most often pointers to tree nodes. Come to think of it, the
+right thing to do is to make the printing of stack values be
+user-definable. It would also be useful to include the filename &
+line# of the file being parsed, but the main filename & line# should
+continue to be that of grammar.y
+
+Anyway, this feature has saved my life on numerous occasions. The way
+I customarily use it is to first run bison with the traces on, isolate
+the sequence of reductions that interests me, put those traces in a
+buffer and force it into compile-mode, then visit each of those lines
+in the grammar and set breakpoints with C-x SPACE. Then, I can run
+again under the control of gdb and stop at each semantic action.
+With the hex addresses of tree nodes, I can inspect the values
+associated with any rhs token.
+
+You like?
+
+* input synclines
+Some users create their foo.y files, and equip them with #line. Bison
+should recognize these, and preserve them.
projects / bison.git / blobdiff