This was demanded several times. See for instance:
- David M. Warme
https://lists.gnu.org/archive/html/help-bison/2011-04/msg00003.html
- box12009
http://lists.gnu.org/archive/html/bug-bison/2016-10/msg00001.html
Basically, this reverts:
- commit 3d3bc1fe30
Get rid of (yy)rhs and (yy)prhs
- commit d333175f63
Avoid compiler warning.
Note that since these tables are not needed in the generated parsers,
no skeleton requests them. This change only brings back their
definition to M4, making it possible to user-defined skeletons to use
these tables.
* src/output.c (muscle_insert_item_number_table): Define.
(prepare_rules): Generate the rhs and prhs tables.
Reported by Rici Lake.
http://lists.gnu.org/archive/html/bug-bison/2018-10/msg00000.html
* src/complain.h: Formatting change.
* src/parse-gram.y (id): Reject character literals used in a context
for non-terminals.
* tests/input.at (Invalid %nterm uses): Check that.
Reported by Uxio Prego.
https://lists.gnu.org/archive/html/help-bison/2018-11/msg00031.html
We also need to move the unreachable 'goto' to a reachable place,
otherwise clang complains about the code being unreachable anyway.
See also https://bugs.llvm.org/show_bug.cgi?id=39736.
Interestingly, we don't have to apply that trick to
`#define YYCDEBUG if (false) std::cerr`, clang does not warn when the
code comes from macro expansion.
* configure.ac: Use -Wunreachable-code when supported.
* data/lalr1.cc, data/yacc.c: Pacify clang's warning about `if (0)`
by using a macro.
Another possibility was to move this statement to a reachable place.
* tests/actions.at, tests/c++.at: Avoid generating unreachable code.
We should probably introduce some struct and functions to deal with
stack management, rather than open coding it. yyparse would be much
nicer to read, and a better model for possible other skeletons.
* data/yacc.c (yyparse::yysetstate): Avoid generating code when
neither yyoverflow nor YYSTACK_RELOCATE is defined.
Currently on a grammar such as
exp : a '1' | a '2' | a '3' | b '1' | b '2' | b '3'
a:
b:
we count only one rr-conflict on the `b:` rule, i.e., we expect:
b: %expect-rr 1
although there are 3 conflicts in total. That's because in the
conflicted state we count only a single conflict, not three (one for
each of the lookaheads: '1', '2', '3').
State 0
0 $accept: . exp $end
1 exp: . a '1'
2 | . a '2'
3 | . a '3'
4 | . b '1'
5 | . b '2'
6 | . b '3'
7 a: . %empty ['1', '2', '3']
8 b: . %empty ['1', '2', '3']
'1' reduce using rule 7 (a)
'1' [reduce using rule 8 (b)]
'2' reduce using rule 7 (a)
'2' [reduce using rule 8 (b)]
'3' reduce using rule 7 (a)
'3' [reduce using rule 8 (b)]
$default reduce using rule 7 (a)
exp go to state 1
a go to state 2
b go to state 3
See https://lists.gnu.org/archive/html/bison-patches/2013-02/msg00106.html.
* src/conflicts.c (rule_has_state_rr_conflicts): Rename as...
(count_rule_state_sr_conflicts): this.
DWIM.
(count_rule_rr_conflicts): Adjust.
* tests/conflicts.at (%expect-rr in grammar rules)
(%expect-rr too much in grammar rules)
(%expect-rr not enough in grammar rules): New.
On a grammar such as
exp: "num" | "num" | "num"
we currently report only one RR conflict, instead of two.
This bug is present since the origins of Bison
commit 08089d5d35
Author: David MacKenzie <djm@djmnet.org>
Date: Tue Apr 20 05:42:52 1993 +0000
Initial revision
and was preserved in
commit 676385e29c
Author: Paul Hilfinger <Hilfinger@CS.Berkeley.EDU>
Date: Fri Jun 28 02:26:44 2002 +0000
Initial check-in introducing experimental GLR parsing. See entry in
ChangeLog dated 2002-06-27 from Paul Hilfinger for details.
See
https://lists.gnu.org/archive/html/bison-patches/2018-11/msg00011.html
* src/conflicts.h, src/conflicts.c (count_state_rr_conflicts)
(count_rr_conflicts): Use only the correct count of conflicts.
* tests/glr-regression.at: Fix expectations.
Currently on a grammar such as
exp: "number" | exp "+" exp | exp "*" exp
we count only one sr-conflict for both binary rules, i.e., we expect:
exp: "number" | exp "+" exp %expect 1 | exp "*" exp %expect 1
although there are 4 conflicts in total. That's because in the states
in conflict, for instance that for the "+" rule:
State 6
2 exp: exp . "+" exp
2 | exp "+" exp . [$end, "+", "*"]
3 | exp . "*" exp
"+" shift, and go to state 4
"*" shift, and go to state 5
"+" [reduce using rule 2 (exp)]
"*" [reduce using rule 2 (exp)]
$default reduce using rule 2 (exp)
we count only a single conflict, although there are two (one on "+"
and another with "*").
See https://lists.gnu.org/archive/html/bison-patches/2013-02/msg00106.html.
* src/conflicts.c (rule_has_state_sr_conflicts): Rename as...
(count_rule_state_sr_conflicts): this.
DWIM.
(count_rule_sr_conflicts): Adjust.
* tests/conflicts.at (%expect in grammar rules): New.
This change allows one to document (and check) which rules participate
in shift/reduce and reduce/reduce conflicts. This is particularly
important GLR parsers, where conflicts are a normal occurrence. For
example,
%glr-parser
%expect 1
%%
...
argument_list:
arguments %expect 1
| arguments ','
| %empty
;
arguments:
expression
| argument_list ',' expression
;
...
Looking at the output from -v, one can see that the shift-reduce
conflict here is due to the fact that the parser does not know whether
to reduce arguments to argument_list until it sees the token AFTER the
following ','. By marking the rule with %expect 1 (because there is a
conflict in one state), we document the source of the 1 overall shift-
reduce conflict.
In GLR parsers, we can use %expect-rr in a rule for reduce/reduce
conflicts. In this case, we mark each of the conflicting rules. For
example,
%glr-parser
%expect-rr 1
%%
stmt:
target_list '=' expr ';'
| expr_list ';'
;
target_list:
target
| target ',' target_list
;
target:
ID %expect-rr 1
;
expr_list:
expr
| expr ',' expr_list
;
expr:
ID %expect-rr 1
| ...
;
In a statement such as
x, y = 3, 4;
the parser must reduce x to a target or an expr, but does not know
which until it sees the '='. So we notate the two possible reductions
to indicate that each conflicts in one rule.
See https://lists.gnu.org/archive/html/bison-patches/2013-02/msg00105.html.
* doc/bison.texi (Suppressing Conflict Warnings): Document %expect,
%expect-rr in grammar rules.
* src/conflicts.c (count_state_rr_conflicts): Adjust comment.
(rule_has_state_sr_conflicts): New static function.
(count_rule_sr_conflicts): New static function.
(rule_nast_state_rr_conflicts): New static function.
(count_rule_rr_conflicts): New static function.
(rule_conflicts_print): New static function.
(conflicts_print): Also use rule_conflicts_print to report on individual
rules.
* src/gram.h (struct rule): Add new fields expected_sr_conflicts,
expected_rr_conflicts.
* src/reader.c (grammar_midrule_action): Transfer expected_sr_conflicts,
expected_rr_conflicts to new rule, and turn off in current_rule.
(grammar_current_rule_expect_sr): New function.
(grammar_current_rule_expect_rr): New function.
(packgram): Transfer expected_sr_conflicts, expected_rr_conflicts
to new rule.
* src/reader.h (grammar_current_rule_expect_sr): New function.
(grammar_current_rule_expect_rr): New function.
* src/symlist.c (symbol_list_sym_new): Initialize expected_sr_conflicts,
expected_rr_conflicts.
* src/symlist.h (struct symbol_list): Add new fields expected_sr_conflicts,
expected_rr_conflicts.
* tests/conflicts.at: Add tests "%expect in grammar rule not enough",
"%expect in grammar rule right.", "%expect in grammar rule too much."
We also lack a consistent naming for directive implementations.
`directive_skeleton` is too long, `percent_skeleton` is not very nice
looking, `process_skeleton` looks ambiguous, `do_skeleton` is somewhat
ambiguous too, but seems a better track.
* src/parse-gram.y (version_check): Rename as...
(do_require): this.
(do_skeleton): New.
Use it.
We may generate code such as
basic_symbol (typename Base::kind_type t, YY_RVREF (std::pair<int,int>) v);
which, of course, breaks, because YY_RVREF sees two arguments. Let's
not play tricks with _VA_ARGS__, I'm unsure about it portability.
Anyway, I plan to change more things in this area.
Reported by Sébastien Villemot.
http://lists.gnu.org/archive/html/bug-bison/2018-11/msg00014.html
* data/variant.hh (b4_basic_symbol_constructor_declare)
(b4_basic_symbol_constructor_define): Don't use macro on user types.
* tests/types.at: Check that we support pairs.
In C++, [[noreturn]] must not be between "static" and the rest of the
function signature, it must precede it. C's _Noreturn does not seem
to have such a constraint, but it is therefore compatible with the C++
constraint. Since we #define _Noreturn as [[noreturn]] is modern C++,
be sure to push the _Noreturn first.
Unfortunately this was not caught by the test suite, because it always
loads config.h first, and config.h contains another definition of
_Noreturn that does not use [[noreturn]], and hides ours. That's
probably a sign we should avoid always loading config.h.
* data/glr.c (yyFail, yyMemoryExhausted): here.
* tests/local.at (AT_LANG_FOR_EACH_STD): New.
(AT_REQUIRE_CXX_VERSION): Rename as...
(AT_REQUIRE_CXX_STD): this.
Accept an argument for what to do when the requirement is not met.
* tests/types.at (api.value.type): Check all the C++ stds.
The following commit introduce even more compilations/runs than
before, and with ASAN on, we go beyond to 50min credit from Travis.
* .travis.yml (Clang 7 libc++ and ASAN): Split in two.
Akim Demaille
Akim Demaille
Paul Hilfinger
Jannick