X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/5458913abab5e33938892b0d279f02f3b09d94db..32288c8cbd309b29dff45e81d78374a5eb9c006e:/NEWS diff --git a/NEWS b/NEWS index c0414a21..a2ea735e 100644 --- a/NEWS +++ b/NEWS @@ -2,13 +2,68 @@ GNU Bison NEWS * Noteworthy changes in release ?.? (????-??-??) [?] +** Incompatible changes + +*** Obsolete features + + Support for YYFAIL is removed (deprecated in Bison 2.4.2). + Support for yystype and yyltype (instead of YYSTYPE and YYLTYPE) + is removed (deprecated in Bison 1.875). + Support for YYPARSE_PARAM is removed (deprecated in Bison 1.875). + ** Warnings -*** Warning categories are now diplayed in warnings +*** Enhancements of the -Werror option - For instance: + The -Werror=CATEGORY option is now recognized, and will treat specified + warnings as errors. The warnings need not have been explicitly activated + using the -W option, this is similar to what GCC 4.7 does. + + For example, given the following command line, Bison will treat both + warnings related to POSIX Yacc incompatibilities and S/R conflicts as + errors (and only those): + + $ bison -Werror=yacc,error=conflicts-sr input.y + + If no categories are specified, -Werror will make all active warnings into + errors. For example, the following line does the same the previous example: + + $ bison -Werror -Wnone -Wyacc -Wconflicts-sr input.y + + (By default -Wconflicts-sr,conflicts-rr,deprecated,other is enabled.) + + Note that the categories in this -Werror option may not be prefixed with + "no-". However, -Wno-error[=CATEGORY] is valid. + + Note that -y enables -Werror=yacc. Therefore it is now possible to require + Yacc-like behavior (e.g., always generate y.tab.c), but to report + incompatibilities as warnings: "-y -Wno-error=yacc". + +*** The display of warnings is now richer + + The option that controls a given warning is now displayed: + + foo.y:4.6: warning: type clash on default action: != [-Wother] - foo.y:4.6: warning: type clash on default action: != [-Wother] + In the case of warnings treated as errors, the prefix is changed from + "warning: " to "error: ", and the suffix is displayed, in a manner similar + to GCC, as [-Werror=CATEGORY]. + + For instance, where the previous version of Bison would report (and exit + with failure): + + bison: warnings being treated as errors + input.y:1.1: warning: stray ',' treated as white space + + it now reports: + + input.y:1.1: error: stray ',' treated as white space [-Werror=other] + +*** Deprecated constructs + + The new 'deprecated' warning category flags obsolete constructs whose + support will be discontinued. It is enabled by default. These warnings + used to be reported as 'other' warnings. *** Useless semantic types @@ -27,18 +82,17 @@ GNU Bison NEWS 3.28-34: warning: type is used, but is not associated to any symbol 4.28-34: warning: type is used, but is not associated to any symbol -*** Undeclared symbols +*** Undefined but unused symbols - Bison used to raise an error for %printer and %destructor directives for - undefined symbols. + Bison used to raise an error for undefined symbols that are not used in + the grammar. This is now only a warning. %printer {} symbol1 %destructor {} symbol2 + %type symbol3 %% exp: "a"; - This is now only a warning. - *** Useless destructors or printers Bison now warns about useless destructors or printers. In the following @@ -53,6 +107,52 @@ GNU Bison NEWS %printer {} token1 %destructor {} token2 +*** Conflicts + + The warnings and error messages about shift/reduce and reduce/reduce + conflicts have been normalized. For instance on the following foo.y file: + + %glr-parser + %% + exp: exp '+' exp | '0' | '0'; + + compare the previous version of bison: + + $ bison foo.y + foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce + $ bison -Werror foo.y + bison: warnings being treated as errors + foo.y: conflicts: 1 shift/reduce, 2 reduce/reduce + + with the new behavior: + + $ bison foo.y + foo.y: warning: 1 shift/reduce conflict [-Wconflicts-sr] + foo.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr] + $ bison -Werror foo.y + foo.y: error: 1 shift/reduce conflict [-Werror=conflicts-sr] + foo.y: error: 2 reduce/reduce conflicts [-Werror=conflicts-rr] + + When %expect or %expect-rr is used, such as with bar.y: + + %expect 0 + %glr-parser + %% + exp: exp '+' exp | '0' | '0'; + + Former behavior: + + $ bison bar.y + bar.y: conflicts: 1 shift/reduce, 2 reduce/reduce + bar.y: expected 0 shift/reduce conflicts + bar.y: expected 0 reduce/reduce conflicts + + New one: + + $ bison bar.y + bar.y: error: shift/reduce conflicts: 1 found, 0 expected + bar.y: error: reduce/reduce conflicts: 2 found, 0 expected + ** Additional yylex/yyparse arguments The new directive %param declares additional arguments to both yylex and @@ -70,11 +170,23 @@ GNU Bison NEWS ** Java skeleton improvements - The constants for token names were moved to the Lexer interface. - Also, it is possible to add code to the parser's constructors using - "%code init" and "%define init_throws". + The constants for token names were moved to the Lexer interface. Also, it + is possible to add code to the parser's constructors using "%code init" + and "%define init_throws". + +** C++ skeletons improvements + +*** The parser header is no longer mandatory (lalr1.cc, glr.cc) + + Using %defines is now optional. Without it, the needed support classes + are defined in the generated parser, instead of additional files (such as + location.hh, position.hh and stack.hh). + +*** Locations are no longer mandatory (lalr1.cc, glr.cc) + + Both lalr1.cc and glr.cc no longer require %location. -** C++ skeleton improvements +*** syntax_error exception (lalr1.cc) The C++ parser features a syntax_error exception, which can be thrown from the scanner or from user rules to raise syntax errors. @@ -83,14 +195,14 @@ GNU Bison NEWS used by the scanner, or rejecting invalid combinations from a factory invoked by the user actions). -** Variable api.tokens.prefix +** Variable api.token.prefix - The variable api.tokens.prefix changes the way tokens are identified in + The variable api.token.prefix changes the way tokens are identified in the generated files. This is especially useful to avoid collisions with identifiers in the target language. For instance %token FILE for ERROR - %define api.tokens.prefix "TOK_" + %define api.token.prefix "TOK_" %% start: FILE for ERROR; @@ -99,34 +211,196 @@ GNU Bison NEWS use these prefixed token names, although the grammar itself still uses the short names (as in the sample rule given above). -** Variable api.namespace +** Renamed %define variables - The "namespace" variable is renamed "api.namespace". Backward + The following variables have been renamed for consistency. Backward compatibility is ensured, but upgrading is recommended. + lr.default-reductions -> lr.default-reduction + lr.keep-unreachable-states -> lr.keep-unreachable-state + namespace -> api.namespace + ** Variable parse.error - The variable error controls the verbosity of error messages. The - use of the %error-verbose directive is deprecated in favor of - %define parse.error "verbose". + This variable controls the verbosity of error messages. The use of the + %error-verbose directive is deprecated in favor of "%define parse.error + verbose". ** Semantic predicates - The new, experimental, semantic-predicate feature allows actions of - the form %?{ BOOLEAN-EXPRESSION }, which cause syntax errors (as for + The new, experimental, semantic-predicate feature allows actions of the + form "%?{ BOOLEAN-EXPRESSION }", which cause syntax errors (as for YYERROR) if the expression evaluates to 0, and are evaluated immediately - in GLR parsers, rather than being deferred. The result is that they - allow the programmer to prune possible parses based on the values of - runtime expressions. + in GLR parsers, rather than being deferred. The result is that they allow + the programmer to prune possible parses based on the values of run-time + expressions. + +** The directive %expect-rr is now an error in non GLR mode + + It used to be an error only if used in non GLR mode, _and_ if there are + reduce/reduce conflicts. * Noteworthy changes in release ?.? (????-??-??) [?] +** Changes in the format of error messages + + This used to be the format of many error reports: + + foo.y:5.10-24: result type clash on merge function 'merge': != + foo.y:4.13-27: previous declaration + + It is now: + + foo.y:5.10-25: result type clash on merge function 'merge': != + foo.y:4.13-27: previous declaration + +** Exception safety (lalr1.cc) + + The parse function now catches exceptions, uses the %destructors to + release memory (the lookahead symbol and the symbols pushed on the stack) + before re-throwing the exception. + + This feature is somewhat experimental. User feedback would be + appreciated. + +** New %define variable: api.location.type (glr.cc, lalr1.cc, lalr1.java) + + The %define variable api.location.type defines the name of the type to use + for locations. When defined, Bison no longer generates the position.hh + and location.hh files, nor does the parser will include them: the user is + then responsible to define her type. + + This can be used in programs with several parsers to factor their location + and position files: let one of them generate them, and the others just use + them. + + This feature was actually introduced, but not documented, in Bison 2.5, + under the name "location_type" (which is maintained for backward + compatibility). + + For consistency, lalr1.java's %define variables location_type and + position_type are deprecated in favor of api.location.type and + api.position.type. + +** Graphviz improvements + + The graphical presentation of the states is more readable: their shape is + now rectangular, the state number is clearly displayed, and the items are + numbered and left-justified. + + The reductions are now explicitly represented as transitions to other + diamond shaped nodes. + +* Noteworthy changes in release 2.6.4 (2012-10-23) [stable] + + Bison 2.6.3's --version was incorrect. This release fixes this issue. + +* Noteworthy changes in release 2.6.3 (2012-10-22) [stable] + +** Bug fixes + + Bugs and portability issues in the test suite have been fixed. + + Some errors in translations have been addressed, and --help now directs + users to the appropriate place to report them. + + Stray Info files shipped by accident are removed. + + Incorrect definitions of YY_, issued by yacc.c when no parser header is + generated, are removed. + + All the generated headers are self-contained. + +** Header guards (yacc.c, glr.c, glr.cc) + + In order to avoid collisions, the header guards are now + YY___INCLUDED, instead of merely _. + For instance the header generated from + + %define api.prefix "calc" + %defines "lib/parse.h" + + will use YY_CALC_LIB_PARSE_H_INCLUDED as guard. + +** Fix compiler warnings in the generated parser (yacc.c, glr.c) + + The compilation of pure parsers (%define api.pure) can trigger GCC + warnings such as: + + input.c: In function 'yyparse': + input.c:1503:12: warning: 'yylval' may be used uninitialized in this + function [-Wmaybe-uninitialized] + *++yyvsp = yylval; + ^ + + This is now fixed; pragmas to avoid these warnings are no longer needed. + + Warnings from clang ("equality comparison with extraneous parentheses" and + "function declared 'noreturn' should not return") have also been + addressed. + +* Noteworthy changes in release 2.6.2 (2012-08-03) [stable] + +** Bug fixes + + Buffer overruns, complaints from Flex, and portability issues in the test + suite have been fixed. + +** Spaces in %lex- and %parse-param (lalr1.cc, glr.cc) + + Trailing end-of-lines in %parse-param or %lex-param would result in + invalid C++. This is fixed. + +** Spurious spaces and end-of-lines + + The generated files no longer end (nor start) with empty lines. + +* Noteworthy changes in release 2.6.1 (2012-07-30) [stable] + + Bison no longer executes user-specified M4 code when processing a grammar. + +** Future Changes + + In addition to the removal of the features announced in Bison 2.6, the + next major release will remove the "Temporary hack for adding a semicolon + to the user action", as announced in the release 2.5. Instead of: + + exp: exp "+" exp { $$ = $1 + $3 }; + + write: + + exp: exp "+" exp { $$ = $1 + $3; }; + +** Bug fixes + +*** Type names are now properly escaped. + +*** glr.cc: set_debug_level and debug_level work as expected. + +*** Stray @ or $ in actions + + While Bison used to warn about stray $ or @ in action rules, it did not + for other actions such as printers, destructors, or initial actions. It + now does. + +** Type names in actions + + For consistency with rule actions, it is now possible to qualify $$ by a + type-name in destructors, printers, and initial actions. For instance: + + %printer { fprintf (yyo, "(%d, %f)", $$, $$); } <*> <>; + + will display two values for each typed and untyped symbol (provided + that YYSTYPE has both "ival" and "fval" fields). + +* Noteworthy changes in release 2.6 (2012-07-19) [stable] + ** Future changes The next major release of Bison will drop support for the following deprecated features. Please report disagreements to bug-bison@gnu.org. -*** K&C parsers +*** K&R C parsers Support for generating parsers in K&R C will be removed. Parsers generated for C support ISO C90, and are tested with ISO C99 and ISO C11 @@ -151,7 +425,7 @@ GNU Bison NEWS because existing versions of ylwrap (e.g., Automake 1.12.1) do not support it. -** Headers +** Generated Parser Headers *** Guards (yacc.c, glr.c, glr.cc) @@ -213,10 +487,19 @@ GNU Bison NEWS # define BAR_FOO_H # define BAR_FOO_H /* Enabling traces. */ /* Enabling traces. */ - # ifndef YYDEBUG # ifndef YYDEBUG - # define YYDEBUG 0 # define YYDEBUG 0 - # endif # endif - # if YYDEBUG # if YYDEBUG + # ifndef YYDEBUG | # ifndef BAR_DEBUG + > # if defined YYDEBUG + > # if YYDEBUG + > # define BAR_DEBUG 1 + > # else + > # define BAR_DEBUG 0 + > # endif + > # else + # define YYDEBUG 0 | # define BAR_DEBUG 0 + > # endif + # endif | # endif + + # if YYDEBUG | # if BAR_DEBUG extern int bar_debug; extern int bar_debug; # endif # endif @@ -1913,7 +2196,8 @@ along with this program. If not, see . LocalWords: namespaces strerror const autoconfiguration Dconst Autoconf's FDL LocalWords: Automake TMPDIR LESSEQ ylwrap endif yydebug YYTOKEN YYLSP ival hh LocalWords: extern YYTOKENTYPE TOKENTYPE yytokentype tokentype STYPE lval pdf - LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp + LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init + LocalWords: TOK calc yyo fval Wconflicts Local Variables: mode: outline