TODO: import from master.

* TODO: Copy the current version.

1 files changed, 182 insertions, 62 deletions

diff --git a/TODO b/TODO
index 5807ccdc..13c1f858 100644
--- a/TODO
+++ b/TODO
@@ -1,8 +1,133 @@
--*- outline -*-
+* Short term
+** Variable names.
+What should we name `variant' and `lex_symbol'?
+
+** Use b4_symbol in all the skeleton
+Move its definition in the more standard places and deploy it in other
+skeletons.  Then remove the older system, including the tables
+generated by output.c
+
+** Update the documentation on gnu.org
+
+** Get rid of fake #lines [Bison: ...]
+Possibly as simple as checking whether the column number is nonnegative.
+
+I have seen messages like the following from GCC.
+
+<built-in>:0: fatal error: opening dependency file .deps/libltdl/argz.Tpo: No such file or directory
+
+
+** Discuss about %printer/%destroy in the case of C++.
+It would be very nice to provide the symbol classes with an operator<<
+and a destructor.  Unfortunately the syntax we have chosen for
+%destroy and %printer make them hard to reuse.  For instance, the user
+is invited to write something like
+
+   %printer { debug_stream() << $$; } <my_type>;
+
+which is hard to reuse elsewhere since it wants to use
+"debug_stream()" to find the stream to use.  The same applies to
+%destroy: we told the user she could use the members of the Parser
+class in the printers/destructors, which is not good for an operator<<
+since it is no longer bound to a particular parser, it's just a
+(standalone symbol).
+
+** Rename LR0.cc
+as lr0.cc, why upper case?
+
+** bench several bisons.
+Enhance bench.pl with %b to run different bisons.
+
+* Various
+** Warnings
+Warnings about type tags that are used in printer and dtors, but not
+for symbols?
+
+** YYERRCODE
+Defined to 256, but not used, not documented.  Probably the token
+number for the error token, which POSIX wants to be 256, but which
+Bison might renumber if the user used number 256.  Keep fix and doc?
+Throw away?
+
+Also, why don't we output the token name of the error token in the
+output?  It is explicitly skipped:
+
+      /* Skip error token and tokens without identifier.  */
+      if (sym != errtoken && id)
+
+Of course there are issues with name spaces, but if we disable we have
+something which seems to be more simpler and more consistent instead
+of the special case YYERRCODE.
+
+   enum yytokentype {
+     error = 256,
+     // ...
+   };
+
+
+We could (should?) also treat the case of the undef_token, which is
+numbered 257 for yylex, and 2 internal.  Both appear for instance in
+toknum:
+
+  const unsigned short int
+  parser::yytoken_number_[] =
+  {
+       0,   256,   257,   258,   259,   260,   261,   262,   263,   264,
+
+while here
+
+   enum yytokentype {
+     TOK_EOF = 0,
+     TOK_EQ = 258,
+
+so both 256 and 257 are "mysterious".
+
+  const char*
+  const parser::yytname_[] =
+  {
+  "\"end of command\"", "error", "$undefined", "\"=\"", "\"break\"",
+
+
+** YYFAIL
+It is seems to be *really* obsolete now, shall we remove it?
+
+** yychar == yyempty_
+The code in yyerrlab reads:
+
+      if (yychar <= YYEOF)
+        {
+          /* Return failure if at end of input.  */
+          if (yychar == YYEOF)
+            YYABORT;
+        }
+
+There are only two yychar that can be <= YYEOF: YYEMPTY and YYEOF.
+But I can't produce the situation where yychar is YYEMPTY here, is it
+really possible?  The test suite does not exercise this case.
+
+This shows that it would be interesting to manage to install skeleton
+coverage analysis to the test suite.
+
+** Table definitions
+It should be very easy to factor the definition of the various tables,
+including the separation bw declaration and definition.  See for
+instance b4_table_define in lalr1.cc.  This way, we could even factor
+C vs. C++ definitions.
+
+* From lalr1.cc to yacc.c
+** Single stack
+Merging the three stacks in lalr1.cc simplified the code, prompted for
+other improvements and also made it faster (probably because memory
+management is performed once instead of three times).  I suggest that
+we do the same in yacc.c.
+
+** yysyntax_error
+The code bw glr.c and yacc.c is really alike, we can certainly factor
+some parts.
 
 * Header guards
 
-From Franc,ois: should we keep the directory part in the CPP guard?
+From François: should we keep the directory part in the CPP guard?
 
 
 * Yacc.c: CPP Macros
@@ -12,18 +137,19 @@ They should not: it is not documented.  But if they need to, let's
 find something clean (not like YYLSP_NEEDED...).
 
 
-* Installation
-
 * Documentation
 Before releasing, make sure the documentation ("Understanding your
 parser") refers to the current `output' format.
 
-* lalr1.cc
-** vector
-Move to using vector, drop stack.hh.
-
 * Report
 
+** Figures
+Some statistics about the grammar and the parser would be useful,
+especially when asking the user to send some information about the
+grammars she is working on.  We should probably also include some
+information about the variables (I'm not sure for instance we even
+specify what LR variant was used).
+
 **  GLR
 How would Paul like to display the conflicted actions?  In particular,
 what when two reductions are possible on a given lookahead token, but one is
@@ -56,7 +182,7 @@ DeRemer and Penello: they already provide the algorithm.
 We should find a means to provide an access to values deep in the
 stack.  For instance, instead of
 
-	baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
+        baz: qux { $$ = $<foo>-1 + $<bar>0 + $1; }
 
 we should be able to have:
 
@@ -71,9 +197,6 @@ must be in the scanner: we must not parse what is in a switched off
 part of %if.  Akim Demaille thinks it should be in the parser, so as
 to avoid falling into another CPP mistake.
 
-** -D, --define-muscle NAME=VALUE
-To define muscles via cli.  Or maybe support directly NAME=VALUE?
-
 ** XML Output
 There are couple of available extensions of Bison targeting some XML
 output.  Some day we should consider including them.  One issue is
@@ -92,13 +215,13 @@ XML output for GNU Bison
 * Unit rules
 Maybe we could expand unit rules, i.e., transform
 
-	exp: arith | bool;
-	arith: exp '+' exp;
-	bool: exp '&' exp;
+        exp: arith | bool;
+        arith: exp '+' exp;
+        bool: exp '&' exp;
 
 into
 
-	exp: exp '+' exp | exp '&' exp;
+        exp: exp '+' exp | exp '&' exp;
 
 when there are no actions.  This can significantly speed up some
 grammars.  I can't find the papers.  In particular the book `LR
@@ -114,7 +237,8 @@ this issue.  Does anybody have it?
 Some history of Bison and some bibliography would be most welcome.
 Are there any Texinfo standards for bibliography?
 
-
+** %printer
+Wow, %printer is not documented.  Clearly mark YYPRINT as obsolete.
 
 * Java, Fortran, etc.
 
@@ -122,19 +246,19 @@ Are there any Texinfo standards for bibliography?
 * Coding system independence
 Paul notes:
 
-	Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
-	255).  It also assumes that the 8-bit character encoding is
-	the same for the invocation of 'bison' as it is for the
-	invocation of 'cc', but this is not necessarily true when
-	people run bison on an ASCII host and then use cc on an EBCDIC
-	host.  I don't think these topics are worth our time
-	addressing (unless we find a gung-ho volunteer for EBCDIC or
-	PDP-10 ports :-) but they should probably be documented
-	somewhere.
+        Currently Bison assumes 8-bit bytes (i.e. that UCHAR_MAX is
+        255).  It also assumes that the 8-bit character encoding is
+        the same for the invocation of 'bison' as it is for the
+        invocation of 'cc', but this is not necessarily true when
+        people run bison on an ASCII host and then use cc on an EBCDIC
+        host.  I don't think these topics are worth our time
+        addressing (unless we find a gung-ho volunteer for EBCDIC or
+        PDP-10 ports :-) but they should probably be documented
+        somewhere.
 
-	More importantly, Bison does not currently allow NUL bytes in
-	tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
-	the source code.  This should get fixed.
+        More importantly, Bison does not currently allow NUL bytes in
+        tokens, either via escapes (e.g., "x\0y") or via a NUL byte in
+        the source code.  This should get fixed.
 
 * --graph
 Show reductions.
@@ -144,15 +268,14 @@ Show reductions.
 ** Skeleton strategy
 Must we keep %token-table?
 
-* src/print_graph.c
-Find the best graph parameters.
-
 * BTYacc
 See if we can integrate backtracking in Bison.  Charles-Henri de
-Boysson <de-boy_c@epita.fr> is working on this, and already has some
-results.  Vadim Maslow, the maintainer of BTYacc was contacted, and we
-stay in touch with him.  Adjusting the Bison grammar parser will be
-needed to support some extra BTYacc features.  This is less urgent.
+Boysson <de-boy_c@epita.fr> has been working on this, but never gave
+the results.
+
+Vadim Maslow, the maintainer of BTYacc was once contacted.  Adjusting
+the Bison grammar parser will be needed to support some extra BTYacc
+features.  This is less urgent.
 
 ** Keeping the conflicted actions
 First, analyze the differences between byacc and btyacc (I'm referring
@@ -167,9 +290,6 @@ very feasible to use the very same conflict tables.
 ** Adjust the skeletons
 Import the skeletons for C and C++.
 
-** Improve the skeletons
-Have them support yysymprint, yydestruct and so forth.
-
 
 * Precedence
 
@@ -178,15 +298,6 @@ It is unfortunate that there is a total order for precedence.  It
 makes it impossible to have modular precedence information.  We should
 move to partial orders (sounds like series/parallel orders to me).
 
-** Correlation b/w precedence and associativity
-Also, I fail to understand why we have to assign the same
-associativity to operators with the same precedence.  For instance,
-why can't I decide that the precedence of * and / is the same, but the
-latter is nonassoc?
-
-If there is really no profound motivation, we should find a new syntax
-to allow specifying this.
-
 ** RR conflicts
 See if we can use precedence between rules to solve RR conflicts.  See
 what POSIX says.
@@ -215,20 +326,6 @@ $<type_name>$ = $<type_name>1. I therefore think that one should implement
 a Bison option where every typed default rule is explicitly written out
 (same typed ruled can of course be grouped together).
 
-Note: Robert Anisko handles this.  He knows how to do it.
-
-
-* Warnings
-It would be nice to have warning support.  See how Autoconf handles
-them, it is fairly well described there.  It would be very nice to
-implement this in such a way that other programs could use
-lib/warnings.[ch].
-
-Don't work on this without first announcing you do, as I already have
-thought about it, and know many of the components that can be used to
-implement it.
-
-
 * Pre and post actions.
 From: Florian Krohm <florian@edamail.fishkill.ibm.com>
 Subject: YYACT_EPILOGUE
@@ -260,6 +357,29 @@ to bison. If you're interested, I'll work on a patch.
 * Better graphics
 Equip the parser with a means to create the (visual) parse tree.
 
+* Complaint submessage indentation.
+We already have an implementation that works fairly well for named
+reference messages, but it would be nice to use it consistently for all
+submessages from Bison.  For example, the "previous definition"
+submessage or the list of correct values for a %define variable might
+look better with indentation.
+
+However, the current implementation makes the assumption that the
+location printed on the first line is not usually much shorter than the
+locations printed on the submessage lines that follow.  That assumption
+may not hold true as often for some kinds of submessages especially if
+we ever support multiple grammar files.
+
+Here's a proposal for how a new implementation might look:
+
+  http://lists.gnu.org/archive/html/bison-patches/2009-09/msg00086.html
+
+
+Local Variables:
+mode: outline
+coding: utf-8
+End:
+
 -----
 
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