X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/2bd435c36c0dfdefb07cef05dec851ec75bab20b..f6df83b4e80b2a53c08b5dc654e247076a3b9b03:/NEWS diff --git a/NEWS b/NEWS index 8da9cf9f..619d36cd 100644 --- a/NEWS +++ b/NEWS @@ -2,6 +2,267 @@ GNU Bison NEWS * Noteworthy changes in release ?.? (????-??-??) [?] +** Incompatible changes + +*** Obsolete features + + Support for YYFAIL is removed (deprecated in Bison 2.4.2): use YYERROR. + + Support for yystype and yyltype is removed (deprecated in Bison 1.875): + use YYSTYPE and YYLTYPE. + + Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison + 1.875): use %lex-param, %parse-param, or %param. + +** Warnings + +*** Carets + + Version 2.7 introduced caret errors, for a prettier output. These are now + activated by default. The old format can still be used by invoking Bison + with -fno-caret (or -fnone). + +*** Enhancements of the -Werror option + + 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] + + 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 + + Bison now warns about useless (uninhabited) semantic types. Since + semantic types are not declared to Bison (they are defined in the opaque + %union structure), it is %printer/%destructor directives about useless + types that trigger the warning: + + %token term + %type nterm + %printer {} + %destructor {} + %% + nterm: term { $$ = $1; }; + + 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 + +*** Undefined but unused 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"; + +*** Useless destructors or printers + + Bison now warns about useless destructors or printers. In the following + example, the printer for , and the destructor for are + useless: all symbols of (token1) already have a printer, and all + symbols of type (token2) already have a destructor. + + %token token1 + token2 + token3 + token4 + %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 + yyparse. The %lex-param, %parse-param, and %param directives support one + or more arguments. Instead of + + %lex-param {arg1_type *arg1} + %lex-param {arg2_type *arg2} + %parse-param {arg1_type *arg1} + %parse-param {arg2_type *arg2} + + one may now declare + + %param {arg1_type *arg1} {arg2_type *arg2} + +** 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". + +** 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. + +*** 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. + This facilitates reporting errors caught in sub-functions (e.g., + rejecting too large integral literals from a conversion function + used by the scanner, or rejecting invalid combinations from a + factory invoked by the user actions). + +*** The epilogue is no longer affected by internal #defines + + The glr.c skeleton uses defines such as #define yylval (yystackp->yyval) in + generated code. These weren't properly undefined before the inclusion of + the user epilogue, so functions such as the following were butchered by the + preprocessor expansion: + + int yylex (yy::parser::semantic_type *yylval); + + This is has been fixed: yylval, ynerrs, yychar, and yylloc are now valid + identifiers for user-provided variables. + +** Renamed %define variables + + 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 + stype -> api.value.type + +** Variable api.token.prefix + + 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.token.prefix "TOK_" + %% + start: FILE for ERROR; + + will generate the definition of the symbols TOK_FILE, TOK_for, and + TOK_ERROR in the generated sources. In particular, the scanner must + use these prefixed token names, although the grammar itself still + uses the short names (as in the sample rule given above). + + + +** Variable parse.error + + 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 + 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 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 2.7 (2012-12-12) [stable] @@ -208,7 +469,7 @@ GNU Bison NEWS * Noteworthy changes in release 2.6.1 (2012-07-30) [stable] - Bison no longer executes user-specified M4 code when processing a grammar. + Bison no longer executes user-specified M4 code when processing a grammar. ** Future Changes @@ -246,7 +507,7 @@ GNU Bison NEWS * Noteworthy changes in release 2.6 (2012-07-19) [stable] -** Future Changes +** Future changes The next major release of Bison will drop support for the following deprecated features. Please report disagreements to bug-bison@gnu.org. @@ -2050,8 +2311,8 @@ 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 calc yyo fval Wmaybe - LocalWords: yyvsp pragmas noreturn java's + LocalWords: lang yyoutput dvi html ps POSIX lvalp llocp Wother nterm arg init + LocalWords: TOK calc yyo fval Wconflicts Local Variables: mode: outline