* src/closure.c, src/print.c, src/reader.c, src/reduce.c:

[bison.git] / TODO

diff --git a/TODO b/TODO
index 62622a61a15a47fe063e05f7dd39b9b9355b76d3..a2057afb2f889d21e211cde7d245983168912840 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,11 +1,63 @@
 -*- outline -*-
 
 -*- 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                []
 ** %no-lines           [ok]
 ** %no-parser          []
 ** %pure-parser                []


@@ -23,9 +75,6 @@ Must we keep %no-parser?
             %token-table?
 *** New skeletons.     []
 
             %token-table?
 *** New skeletons.     []
 

-* src/macrotab.[ch]
-Removing warnings when compiling. (gcc-warnings).      [ok]
-

 * src/print_graph.c
 Find the best graph parameters.        []
 
 * src/print_graph.c
 Find the best graph parameters.        []
 


@@ -36,7 +85,63 @@ informations about ERROR_VERBOSE.    []
 skeleton muscles.      []
 %skeleton.             []
 
 skeleton muscles.      []
 %skeleton.             []
 

-* testsuite.
-** tests/reduce.at     [ok]
+* testsuite

 ** tests/pure-parser.at        []
 New tests.
 ** 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.