* data/skeletons/bison.m4, data/skeletons/c++.m4, data/skeletons/c.m4,
* data/skeletons/glr.cc, data/skeletons/lalr1.cc,
* data/skeletons/lalr1.d, data/skeletons/lalr1.java:
Refer to the "kind" of a symbol, not its "type", where appropriate.
Currently we define enumerators only for symbols that have an
identifier. That rules out tokens such as '+', and nonterminals such
as foo-bar and foo.bar. As a consequence we are taking chances: the
compiler might compile yysymbol_type_t as too small an integral type
for some symbol codes.
* data/skeletons/bison.m4 (b4_symbol_sid): Forge a unique symbol
identifier for symbols that don't have an ID.
This is not only cleaner, it also protects us from mixing signed
values (YYEMPTY is #defined as -2) with unsigned types (the
yysymbol_type_t enum is typically compiled as a small unsigned).
For instance GCC 9:
input.c: In function 'yyparse':
input.c:1107:7: error: conversion to 'unsigned int' from 'int'
may change the sign of the result
[-Werror=sign-conversion]
1107 | yyn += yytoken;
| ^~
input.c:1107:10: error: conversion to 'int' from 'unsigned int'
may change the sign of the result
[-Werror=sign-conversion]
1107 | yyn += yytoken;
| ^~~~~~~
input.c:1108:47: error: comparison of integer expressions of
different signedness:
'yytype_int8' {aka 'const signed char'} and
'yysymbol_type_t' {aka 'enum yysymbol_type_t'}
[-Werror=sign-compare]
1108 | if (yyn < 0 || YYLAST < yyn || yycheck[yyn] != yytoken)
| ^~
input.c:702:25: error: operand of ?: changes signedness from 'int'
to 'unsigned int' due to unsignedness of
other operand [-Werror=sign-compare]
702 | #define YYEMPTY (-2)
| ^~~~
input.c:1220:33: note: in expansion of macro 'YYEMPTY'
1220 | yytoken = yychar == YYEMPTY ? YYEMPTY : YYTRANSLATE (yychar);
| ^~~~~~~
input.c:1220:41: error: unsigned conversion from 'int' to
'unsigned int' changes value
from '-2' to '4294967294'
[-Werror=sign-conversion]
1220 | yytoken = yychar == YYEMPTY ? YYEMPTY : YYTRANSLATE (yychar);
| ^
Eventually, it might be interesting to move away from -2 (which is the
only possible negative symbol number) and use the next available
number, to save bits. We could actually even simply use "0" and shift
the rest, which would allow to write "!yytoken" to mean really
"yytoken != YYEMPTY".
* data/skeletons/c.m4 (b4_declare_symbol_enum): Define YYSYMBOL_YYEMPTY.
* data/skeletons/yacc.c: Use it.
* src/parse-gram.y (yyreport_syntax_error): Use YYSYMBOL_YYEMPTY, not
YYEMPTY, when dealing with a symbol.
* tests/regression.at: Adjust.
There's a number of advantage in exposing the symbol (internal)
numbers:
- custom error messages can use them to decide how to represent a
given symbol, or a set of symbols.
- we need something similar in uses of yyexpected_tokens. For
instance, currently, bistromathic's completion() reads:
int ntokens = expected_tokens (line, tokens, YYNTOKENS);
[...]
for (int i = 0; i < ntokens; ++i)
if (tokens[i] == YYTRANSLATE (TOK_VAR))
[...]
else if (tokens[i] == YYTRANSLATE (TOK_FUN))
[...]
else
[...]
- now that it's a compile-time expression, we can easily build static
tables, switch, etc.
- some users depended on the ability to get the token number from a
symbol to write test cases for their scanners. But Bison 3.5
removed the table this feature depended upon (a reverse
yytranslate). Now they can check against the actual symbol number,
without having pay (space and time) a conversion.
See https://lists.gnu.org/r/bug-bison/2020-01/msg00001.html, and
https://lists.gnu.org/archive/html/bug-bison/2020-03/msg00015.html.
- it helps us clearly separate the internal symbol numbers from the
external token numbers, whose difference is sometimes blurred in the
code when values coincide (e.g. "yychar = yytoken = YYEOF").
- it allows us to get rid of ugly macros with inconsistent names such
as YYUNDEFTOK and YYTERROR, and to group related definitions
together.
- similarly it provides a clean access to the $accept symbol (which
proves convenient in a current experimentation of mine with several
%start symbols).
Let's declare this type as a private type (in the *.c file, not
the *.h one). So it does not need to be influenced by the api prefix.
* data/skeletons/bison.m4 (b4_symbol_sid): New.
(b4_symbol): Use it.
* data/skeletons/c.m4 (b4_symbol_enum, b4_declare_symbol_enum): New.
* data/skeletons/yacc.c: Use b4_declare_symbol_enum.
(YYUNDEFTOK, YYTERROR): Remove.
Use the corresponding symbol enum instead.
* doc/bison.texi (Tokens from Literals): Move to code using
%token-table to...
(Decl Summary: %token-table): here.
* data/skeletons/bison.m4: Implement mutual exclusion.
* tests/input.at: Check it.
* doc/local.mk: Be robust to the removal of doc/.
parse.error has more than two possible values.
* data/skeletons/bison.m4 (b4_error_verbose_if, b4_error_verbose_flag):
Remove.
(b4_parse_error_case, b4_parse_error_bmatch): New.
Adjust dependencies.
We used to emit:
/** Token number,to be returned by the scanner. */
static final int NUM = 258;
/** Token number,to be returned by the scanner. */
static final int NEG = 259;
with no space after the comma. Fix that.
* data/skeletons/bison.m4 (b4_token_format): Quote where appropriate.
"detailed" error messages are almost like "verbose", except that we
don't double escape them, they don't get inner quotes, we don't use
yytnamerr, and we hide the table.
"custom" is exposed with the "detailed" tokens, not the "verbose"
ones: they are not double-quoted.
Because there's a risk that some people use yytname even without
"verbose", let's keep yytname (instead of yys_name) in "simple"
parse.error.
* src/output.c (prepare_symbol_names): Be ready to output symbol names
unquoted.
(prepare_symbol_names): Output both the old tname table, and the new
symbol_names one.
* data/skeletons/bison.m4: Accept 'detailed'.
* data/skeletons/yacc.c: When parse.error is 'detailed', don't emit
yytname and yytnamerr, just yysymbol_name with the table inside.
* tests/calc.at: Adjust.
When parse.error is custom, let users define a yyreport_syntax_error
function, and use it.
* data/skeletons/bison.m4 (b4_error_verbose_if): Accept 'custom'.
* data/skeletons/yacc.c: Implement it.
* examples/c/calc/calc.y: Experiment with it.
Bison used to feature %raw, documented as follows:
@item %raw
The output file @file{@var{name}.h} normally defines the tokens with
Yacc-compatible token numbers. If this option is specified, the
internal Bison numbers are used instead. (Yacc-compatible numbers start
at 257 except for single character tokens; Bison assigns token numbers
sequentially for all tokens starting at 3.)
Unfortunately, as far as I can tell, it never worked: token numbers
are indeed changed in the generated tables (from external token number
to internal), yet the code was still applying the mapping from
external token numbers to internal token numbers.
This commit reintroduces the feature as it was expected to be.
* data/skeletons/bison.m4 (b4_token_format): When api.token.raw is
enabled, use the internal token number.
* data/skeletons/yacc.c (yytranslate): Don't emit if api.token.raw is
enabled.
(YYTRANSLATE): Adjust.
Reported by Balázs Scheidler.
* data/skeletons/c.m4 (b4_location_type_define): Use api.location.type
if defined.
* doc/bison.texi: Document it.
* tests/local.at (AT_C_IF, AT_LANG_CASE): New.
Support Span in C.
* tests/calc.at (Span): Convert it to be usable in C and C++.
Check api.location.type with yacc.c and glr.c.
Currently, with --no-lines, instead of "#line file line\n", we emit
"\n". Let's emit nothing.
* data/skeletons/bison.m4 (b4_syncline): Emit at end-of-line when enabled.
* data/skeletons/bison.m4, data/skeletons/c.m4, data/skeletons/glr.cc,
* data/skeletons/lalr1.cc, src/output.c: Use dnl after b4_syncline to
avoid spurious empty lines.
* tests/synclines.at (Sync Lines): Make sure that --no-lines is like
grep -v #line.
* tests/calc.at: Make sure that a rich grammar file behaves properly
with %no-lines.
Currently we use the syncline to report errors about a symbol's
destructor/printer. This is not accurate (only file and line), and
this is incorrect: the file name is double quotes (a recent change,
needed to make sure we escape properly double quotes in it). And
worst of all: with --no-line, b4_syncline expands to nothing.
Rather, push the locations into the backend, and use them.
* src/muscle-tab.h, src/muscle-tab.c (muscle_location_grow): Make it
public.
* src/output.c (prepare_symbol_definitions): Use it to pubish the
location of the printer and destructor.
* data/skeletons/lalr1.java: Use complain_at instead of complain.
* tests/java.at (Java invalid directives): Adjust expectations.
* data/skeletons/bison.m4 (b4_symbol_action_location): Remove.
We should not use b4_syncline this way.
Currently we generate things like:
#line 683 "src/parse-gram.y" /* yacc.c:316 */
The first part is of course very important: compilers point the users
to their grammar file rather than into the generated parser. The
second part points to the place in the skeletons that generated this
piece of code.
This dependency on the Bison skeletons generates lots of useless 'git
diff'. This location is useless for the regular user (who does not
care about the skeletons) and is actually not useful for Bison
developpers too (I never used this to locate the code in skeletons
that generated output). So disable it completely. If someone thinks
this was actually useful, a %define variable should be provided to
control the level of verbosity of '#line', in replacement of
--no-lines.
So now, generate:
#line 683 "src/parse-gram.y"
* data/skeletons/bison.m4 (b4_sync_end): Emit nothing.
Since Bison 3.3, semantic values in rule actions (i.e., '$...') are
passed to the m4 backend as the symbol number. Unfortunately, when
there are unused symbols, the symbols are renumbered _after_ the
numbers were used in the rule actions. As a result, the evaluation of
the skeleton failed because it used non existing symbol numbers.
Which is the happy scenario: we could use numbers of other existing
symbols...
Reported by Balázs Scheidler.
http://lists.gnu.org/archive/html/bug-bison/2019-01/msg00044.html
Translating the rule actions after the symbol renumbering moves too
many parts in bison. Relying on the symbol identifiers is more
troublesome than it might first seem: some don't have an
identifier (tokens with only a literal string), some might have a
complex one (tokens with a literal string with characters special for
M4). Well, these are tokens, but nterms also have issues: "dummy"
nterms (for midrule actions) are named $@32 etc. which is risky for
M4.
Instead, let's simply give M4 the mapping between the old numbers and
the new ones. To avoid confusion between old and new numbers, always
emit pre-renumbering numbers as "orig NUM".
* data/README: Give details about "orig NUM".
* data/skeletons/bison.m4 (__b4_symbol, _b4_symbol): Resolve the
"orig NUM".
* src/output.c (prepare_symbol_definitions): Pass nterm_map to m4.
* src/reduce.h, src/reduce.c (nterm_map): Extract it from
nonterminals_reduce, to make it public.
(reduce_free): Free it.
* src/scan-code.l (handle_action_dollar): When referring to a nterm,
use "orig NUM".
* tests/reduce.at (Useless Parts): New, based Balázs Scheidler's
report.
