Using #define YYSTYPE has always been strongly discouraged in C++.
Macros are dangerous and can result in subtle bugs.
https://lists.gnu.org/r/bug-bison/2020-12/msg00007.html
Maybe some people are currently using #define YYSTYPE. Instead of
dropping support right now, first issue a warning. Bison can "see" if
YYDEBUG is defined (it could even be on the command line), only the
compiler knows. Unfortunately `#warning` is non-portable, and
actually GCC even dies on it when `-pedantic` is enabled. So we need
to use `#pragma message`. We must make it conditional as some
compilers might not support it, but it doesn't matter if only _some_
compilers emit the warning: it should be enough to catch the attention
of the developers.
* data/skeletons/c++.m4: Issue a warning when the user defined
YYSTYPE.
* tests/actions.at: Don't #define YYSTYPE.
* tests/headers.at (Several parsers): Ignore the YYSTYPE in the
warning.
* data/skeletons/glr2.cc, data/skeletons/lalr1.cc (b4_lex): Don't
refer to YYSTYPE, but to value_type.
Note that this is "symbolic" in the sense that these values are never
used by b4_function_call.
* data/skeletons/bison.m4 (b4_union_if): New.
Remove support for "%define variant", which was deprecated long ago.
* tests/local.at (AT_UNION_IF): New.
Currently glr2.cc does not use 'symbol's everywhere, in various places
it also uses yykind, yyval and yyloc "by hand". So we need two
different calls for user-defined constructors: once for ~symbol,
another for yy_destroy_. Both need to call the user destructors with
different calling conventions.
* data/skeletons/glr2.cc (b4_symbol_action): Rename as...
(b4_symbol_action_for_yyval): this.
(b4_symbol_action): New, taken from lalr1.cc.
(yy_destroy_, yy_symbol_value_print_): Use b4_symbol_action_for_yyval.
Three new commits:
commit 8358090292
Author: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed Jan 20 18:30:16 2021 -0800
c: port to HP-UX 11.23
commit 2c294c1325
Author: Vincent Imbimbo <vmi6@cornell.edu>
Date: Sat Jan 23 13:25:18 2021 -0500
cex: fix state-item pruning
commit c22902e360
Author: Akim Demaille <akim.demaille@gmail.com>
Date: Sat Jan 23 18:40:15 2021 +0100
tables: fix handling for useless tokens
Reported by Jot Dot.
https://lists.gnu.org/r/help-bison/2020-12/msg00014.html
* data/skeletons/glr.c, data/skeletons/glr2.cc (b4_call_merger): Use
the symbol's slot, not its type.
* examples/c/glr/c++-types.y: Use explicit per-symbol typing together
with api.value.type=union.
(yylex): Use yytoken_kind_t.
Don't generate C code from bison, leave that to the skeletons.
* src/output.c (merger_output): Emit invocations to b4_call_merger.
* data/skeletons/glr.c (b4_call_merger): New.
This macro is not exposed to users, make start it with 'YY_'.
* data/skeletons/bison.m4, data/skeletons/c.m4, data/skeletons/glr.c,
* data/skeletons/glr.cc, data/skeletons/lalr1.cc,
* src/parse-gram.c, tests/actions.at, tests/c++.at, tests/headers.at,
* tests/local.at (YYUSE): Rename as...
(YY_USE): this.
When using glr.cc, the C function yyparse is an internal detail that
should not be exposed. Users might call it by accident (I did).
* data/skeletons/glr.c (yyparse): When used for glr.cc, rename as yy_parse_impl.
* data/skeletons/glr.cc: Adjust.
* data/skeletons/lalr1.d (YYLocation.step): New.
* examples/d/calc/calc.y (Lexer): Reduce scopes to avoid uninitialized
varibles.
Factor the handling of locations.
We don't need lenChars.
Suggested by Joe Nelson <joe@begriffs.com>.
https://lists.gnu.org/r/help-bison/2020-12/msg00020.html
* data/skeletons/glr.c, data/skeletons/yacc.c (YYNOMEM): New.
Use it.
(yyexhaustedlab): Rename as...
(yynomemlab): this.
* tests/calc.at: Check it.
* doc/bison.texi: Document it.
Fix incorrect statements about non-existing constants for YYERROR etc.
I am not aware of people subclassing the parser class, and I fail to
see how this could be useful. Rather than leaving a badly baked
feature (as in glr.cc currently), let's not support it at all, until
someone comes and explains why and how it would be useful.
* data/skeletons/glr2.cc (parser): We need no virtual function members.
It's on purpose that I keep the `this->` now. We'll see later if we
want to remove them.
* data/skeletons/glr2.cc (yygetToken): Move into...
(glr_stack::yyget_token): this.
(b4_lex): Adjust.
Currently we have two classes that actually should be fused together:
parser and glr_stack. Both carry part of the parsing: (i) parser
contains `parse`, which is the top-level of the parsing process, it
uses yygetToken, etc., and (ii) glr_stack takes care of all the
details (dealing with the stack), and also calls yygetToken.
However if we fuse them together, we would get a large parser class,
in the header file. So it is probably better to split this large
class using the pimpl idiom. But then it appears that glr_stack is
very close from being the impl of parser.
Let's improve this.
For a start...
* data/skeletons/glr2.cc (parser::parse): Move to...
(glr_stack::parse): here.
(parser::parse): Use it.
* data/skeletons/glr2.cc: We no longer play dirty tricks with
parse-params, remove the now useless dance around them.
We now have genuine objects for locations, leave the initial action
alone.
* data/skeletons/glr2.cc: Add support for api.token.constructor.
* examples/c++/glr/c++-types.yy: Use it.
* examples/c++/glr/c++-types.test: Adjust expectations for error
messages.
* data/skeletons/c++.m4 (b4_yytranslate_define): Use static_cast
rather than the YY_CAST macro.
Avoids the need to define YY_CAST in the header.
* data/skeletons/glr2.cc: Fix calls to b4_shared_declarations: pass
the type of file we are in.
Don't define YYTRANSLATE.
(parser::yytranslate_): New, as in lalr1.cc.
Adjust to use it.
* tests/glr-regression.at: Adjust.
Instead of tracking the lookahead with yychar, use yytoken. This is
consistent with lalr1.cc, saves us from calls to YYTRANSLATE (except
when calling yylex), and makes it easier to migrate to using
symbol_type.
* data/skeletons/glr2.cc: Replace all uses of `int yychar` with
`symbol_kind_type yytoken`.
(yygetToken): Don't take/return the lookahead's token-kind and
symbol-kind, just work directly on yystack's `yytoken` member.
* tests/glr-regression.at (AT_PRINT_LOOKAHEAD_DECLARE)
(AT_PRINT_LOOKAHEAD_DEFINE): New.
Adjust to the fact that we have yytoken, not yychar, in glr2.cc.
* data/skeletons/glr2.cc (b4_symbol_action): New, so that we use
`yyval` and `yyloc` rather than the `yyvaluep` and `yylocationp`
pointers.
(yy_symbol_value_print_, yy_symbol_print_, yy_destroy_): Use
references rather than pointers.
Drop support for the undocumented, obsolete, `yyoutput` variable.
Adjust callers.
(glr_state::destroy): Don't use yy_symbol_print_ when we don't have a
symbol. Rather, write dedicated code.
Without the history, D should not support this option. Before the
removal, 'detailed' and 'verbose' options generated the same code.
* data/skeletons/lalr1.d: Here.
* doc/bison.texi: Adapt tests to use 'detailed' instead of 'verbose'.
* tests/calc.at: Document it.
Currently we display the addresses of the semantic values. Instead,
print the values.
Add support for YY_USE across languages.
* data/skeletons/c.m4, data/skeletons/d.m4 (b4_use): New.
* data/skeletons/bison.m4 (b4_symbol_actions): Use b4_use to be
portable to D.
Add support for %printer, and use it.
* data/skeletons/d.m4: Instead of duplicating what's already in
c-like.m4, include it.
(b4_symbol_action): New.
Differs from the one in bison.m4 in that it uses yyval/yyloc instead
of *yyvaluep and *yylocationp.
* data/skeletons/lalr1.d (yy_symbol_print): Avoid calls to formatting,
just call write directly.
Use the %printer.
* examples/d/calc/calc.y: Specify a printer.
Enable traces when $YYDEBUG is set.
* tests/calc.at: Fix the use of %printer with D.
The D parser implements this feature similarly to the C parser,
by using Gettext. Functions gettext() and dgettext() are
imported using extern(C). The internationalisation uses yysymbol_name
to report the name of the SymbolKinds.
* data/skeletons/d.m4 (SymbolKind.toString.yytranslatable,
SymbolKind.toString.yysymbol_name: New), data/skeletons/lalr1.d: Here.
* doc/bison.texi: Document it.
* tests/calc.at: Test it.
(Bison) Variants are extremely picky, which makes them both
annoying (lots of micro-details must be taken care of) and
precious (all the micro-details must be taken care of, in particular
object lifetime).
So (i) each time a semantic value is stored, it must be stored in a
place that exists, and (ii) each time a semantic value is discarded,
its place must have been emptied.
Example of (i)
- new (&yys.value ()) value_type (s->value ());
+ {]b4_variant_if([[
+ new (&yys.value ()) value_type ();
+ ]b4_symbol_variant([yy_accessing_symbol (s->yylrState)],
+ [yys.value ()], [copy], [s->value ()])], [[
+ new (&yys.value ()) value_type (s->value ());]])[
+ }
Example of (ii)
yyparser.yy_destroy_ ("Error: discarding",
- yytoken, &yylval]b4_locations_if([, &yylloc])[);
+ yytoken, &yylval]b4_locations_if([, &yylloc])[);]b4_variant_if([[
+ // Value type destructor.
+ ]b4_symbol_variant([[YYTRANSLATE (this->yychar)]], [[yylval]], [[template destroy]])])[
this->yychar = ]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(empty, id)[;
However, in some places we must not be "pure". In particular:
glr_stack_item (const glr_stack_item& other) YY_NOEXCEPT YY_NOTHROW
: is_state_ (other.is_state_)
{
std::memcpy (raw_, other.raw_, union_size);
}
still must use memcpy, because the constructor would change pred, and
it must not. This constructor is used only when resizing the stack,
in which case pred (which is relative) must not be "adjusted".
The result works, but is messy. Its verbosity comes from at least two
factors:
- we don't have support for complete symbols (binding kind, value and
location), and we should at least try to have it. That simplified
lalr1.cc a lot.
- I have not tried to be smart and use 'move' when possible. As a
consequence many places have 'copy' and then 'destroy'. That kind
of clean up can be done once everything appears to be solid.
* data/skeletons/glr2.cc: Be more rigorous in object lifetime.
In particular, don't forget to discard the lookahead when we're done
with it.
Call variant routines where needed.
Deal with plenty of details.
(b4_call_merger): Add support for variants.
Use references in mergers, rather than pointers.
* examples/c++/glr/c++-types.yy: Exercise variants.
This macro is not exposed to users, make start it with 'YY_'.
* data/skeletons/bison.m4, data/skeletons/c.m4, data/skeletons/glr.c,
* data/skeletons/glr.cc, data/skeletons/glr2.cc, data/skeletons/lalr1.cc,
* src/parse-gram.c, tests/actions.at, tests/c++.at, tests/headers.at,
* tests/local.at (YYUSE): Rename as...
(YY_USE): this.
See "glr.c: log the execution of deferred actions".
* data/skeletons/glr2.cc (yyuserAction): Take yyk as a new argument.
Rename argument yyn as yyrule for clarity.
Log before and after the user action.
Adjust callers to not call YY_REDUCE_PRINT and YY_SYMBOL_PRINT.
