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.
It is unfortunate that %error_verbose was properly diagnosed as
obsoleted by "%define parse.error verbose", but %error-verbose was
not.
* src/parse-gram.y (%error-verbose): Remove support.
* src/scan-gram.l: Do it here instead, with a warning.
* tests/input.at (Deprecated directives): Check it.
These tests are skipped with GCC:
"\"".c:1:5: error: function declaration isn't a prototype [-Werror=strict-prototypes]
int main() { return 0; }
^~~~
* tests/synclines.at: Stop writing C++ in C.
* tests/local.at: Formatting changes.
* src/parse-gram.y (api.value.type): Set to union.
Replace occurrences of %union with explicit %types.
* src/scan-gram.l: Adjust yylval's field names.
(RETURN_VALUE): No longer needs the Field argument.
Use it more.
Support for DJGPP was announced to be removed in the NEWS of Bison
3.1 (2018-08-27) unless someone expressed interest. There was no answer.
* djgpp: Remove.
* NEWS, Makefile.am, cfg.mk, po/POTFILES.in: Adjust.
