X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/8458a411446e5b99106549b2e141c16b697d2836..9cdcbdf2cfb219dac9984026fe61ffc2e394f914:/NEWS diff --git a/NEWS b/NEWS index 5b6ea0c5..eae4fff2 100644 --- a/NEWS +++ b/NEWS @@ -2,15 +2,14 @@ GNU Bison NEWS * Noteworthy changes in release ?.? (????-??-??) [?] -** WARNING: Future backward-incompatibilities! +** Java skeleton improvements - Bison will stop adding a semicolon at the end of the actions (as announced - in the release 2.5): + The Java skeleton now supports push parsing. + Contributed by Dennis Heimbigner. - foo.y:2.22: warning: a ';' might be needed at the end of action code - exp: "num" { $$ = $1 } - ^ - foo.y:2.22: future versions of Bison will not add the ';' +* Noteworthy changes in release 2.7.90 (2013-05-30) [beta] + +** WARNING: Future backward-incompatibilities! Like other GNU packages, Bison will start using some of the C99 features for its own code, especially the definition of variables after statements. @@ -28,9 +27,32 @@ GNU Bison NEWS Support for YYLEX_PARAM and YYPARSE_PARAM is removed (deprecated in Bison 1.875): use %lex-param, %parse-param, or %param. + Missing semicolons at the end of actions are no longer added (as announced + in the release 2.5). + +*** Use of YACC='bison -y' + + TL;DR: With Autoconf <= 2.69, pass -Wno-yacc to (AM_)YFLAGS if you use + Bison extensions. + + Traditional Yacc generates 'y.tab.c' whatever the name of the input file. + Therefore Makefiles written for Yacc expect 'y.tab.c' (and possibly + 'y.tab.h' and 'y.outout') to be generated from 'foo.y'. + + To this end, for ages, AC_PROG_YACC, Autoconf's macro to look for an + implementation of Yacc, was using Bison as 'bison -y'. While it does + ensure compatible output file names, it also enables warnings for + incompatibilities with POSIX Yacc. In other words, 'bison -y' triggers + warnings for Bison extensions. + + Autoconf 2.70+ fixes this incompatibility by using YACC='bison -o y.tab.c' + (which also generates 'y.tab.h' and 'y.output' when needed). + Alternatively, disable Yacc warnings by passing '-Wno-yacc' to your Yacc + flags (YFLAGS, or AM_YFLAGS with Automake). + ** Bug fixes -*** The epilogue is no longer affected by internal #defines +*** The epilogue is no longer affected by internal #defines (glr.c) The glr.c skeleton uses defines such as #define yylval (yystackp->yyval) in generated code. These weren't properly undefined before the inclusion of @@ -39,7 +61,7 @@ GNU Bison NEWS int yylex (YYSTYPE *yylval); - This is has been fixed: yylval, yynerrs, yychar, and yylloc are now valid + This is fixed: yylval, yynerrs, yychar, and yylloc are now valid identifiers for user-provided variables. *** stdio.h is no longer needed when locations are enabled (yacc.c) @@ -47,6 +69,8 @@ GNU Bison NEWS Changes in Bison 2.7 introduced a dependency on FILE and fprintf when locations are enabled. This is fixed. +*** Warnings about useless %pure-parser/%define api.pure are restored + ** Diagnostics reported by Bison Most of these features were contributed by Théophile Ranquet and Victor @@ -58,6 +82,29 @@ GNU Bison NEWS activated by default. The old format can still be used by invoking Bison with -fno-caret (or -fnone). + Some error messages that reproduced excerpts of the grammar are now using + the caret information only. For instance on: + + %% + exp: 'a' | 'a'; + + Bison 2.7 reports: + + in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] + in.y:2.12-14: warning: rule useless in parser due to conflicts: exp: 'a' [-Wother] + + Now bison reports: + + in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] + in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother] + exp: 'a' | 'a'; + ^^^ + + and "bison -fno-caret" reports: + + in.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr] + in.y:2.12-14: warning: rule useless in parser due to conflicts [-Wother] + *** Enhancements of the -Werror option The -Werror=CATEGORY option is now recognized, and will treat specified @@ -198,6 +245,11 @@ GNU Bison NEWS bar.y: error: shift/reduce conflicts: 1 found, 0 expected bar.y: error: reduce/reduce conflicts: 2 found, 0 expected +** Incompatibilities with POSIX Yacc + + The 'yacc' category is no longer part of '-Wall', enable it explicitly + with '-Wyacc'. + ** Additional yylex/yyparse arguments The new directive %param declares additional arguments to both yylex and @@ -213,44 +265,22 @@ GNU Bison NEWS %param {arg1_type *arg1} {arg2_type *arg2} -** Java skeleton improvements - - Contributed by Paolo Bonzini. +** Types of values for %define variables - 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". + Bison used to make no difference between '%define foo bar' and '%define + foo "bar"'. The former is now called a 'keyword value', and the latter a + 'string value'. A third kind was added: 'code values', such as '%define + foo {bar}'. -** C++ skeletons improvements + Keyword variables are used for fixed value sets, e.g., -*** 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. + %define lr.type lalr -*** syntax_error exception (lalr1.cc) + Code variables are used for value in the target language, e.g., - 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). + %define api.value.type {struct semantic_type} -** 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 + String variables are used remaining cases, e.g. file names. ** Variable api.token.prefix @@ -259,7 +289,7 @@ GNU Bison NEWS with identifiers in the target language. For instance %token FILE for ERROR - %define api.token.prefix "TOK_" + %define api.token.prefix {TOK_} %% start: FILE for ERROR; @@ -268,12 +298,95 @@ 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.value.type + + This new %define variable supersedes the #define macro YYSTYPE. The use + of YYSTYPE is discouraged. In particular, #defining YYSTYPE *and* either + using %union or %defining api.value.type results in undefined behavior. + + Either define api.value.type, or use "%union": + + %union + { + int ival; + char *sval; + } + %token INT "integer" + %token STRING "string" + %printer { fprintf (yyo, "%d", $$); } + %destructor { free ($$); } + + /* In yylex(). */ + yylval.ival = 42; return INT; + yylval.sval = "42"; return STRING; + + The %define variable api.value.type supports both keyword and code values. + + The keyword value 'union' means that the user provides genuine types, not + union member names such as "ival" and "sval" above (WARNING: will fail if + -y/--yacc/%yacc is enabled). + + %define api.value.type union + %token INT "integer" + %token STRING "string" + %printer { fprintf (yyo, "%d", $$); } + %destructor { free ($$); } + + /* In yylex(). */ + yylval.INT = 42; return INT; + yylval.STRING = "42"; return STRING; + + The keyword value variant is somewhat equivalent, but for C++ special + provision is made to allow classes to be used (more about this below). + + %define api.value.type variant + %token INT "integer" + %token STRING "string" + + Code values (in braces) denote user defined types. This is where YYSTYPE + used to be used. + + %code requires + { + struct my_value + { + enum + { + is_int, is_string + } kind; + union + { + int ival; + char *sval; + } u; + }; + } + %define api.value.type {struct my_value} + %token INT "integer" + %token STRING "string" + %printer { fprintf (yyo, "%d", $$); } + %destructor { free ($$); } + + /* In yylex(). */ + yylval.u.ival = 42; return INT; + yylval.u.sval = "42"; return STRING; + ** 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". +** 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 + ** Semantic predicates Contributed by Paul Hilfinger. @@ -290,11 +403,212 @@ GNU Bison NEWS It used to be an error only if used in non GLR mode, _and_ if there are reduce/reduce conflicts. -** Token numbering has changed to preserve the user-defined order +** Tokens are numbered in their order of appearance + + Contributed by Valentin Tolmer. + + With '%token A B', A had a number less than the one of B. However, + precedence declarations used to generate a reversed order. This is now + fixed, and introducing tokens with any of %token, %left, %right, + %precedence, or %nonassoc yields the same result. + + When mixing declarations of tokens with a litteral character (e.g., 'a') + or with an identifier (e.g., B) in a precedence declaration, Bison + numbered the litteral characters first. For example + + %right A B 'c' 'd' + + would lead to the tokens declared in this order: 'c' 'd' A B. Again, the + input order is now preserved. + + These changes were made so that one can remove useless precedence and + associativity declarations (i.e., map %nonassoc, %left or %right to + %precedence, or to %token) and get exactly the same output. + +** Useless precedence and associativity + + Contributed by Valentin Tolmer. + + When developing and maintaining a grammar, useless associativity and + precedence directives are common. They can be a nuisance: new ambiguities + arising are sometimes masked because their conflicts are resolved due to + the extra precedence or associativity information. Furthermore, it can + hinder the comprehension of a new grammar: one will wonder about the role + of a precedence, where in fact it is useless. The following changes aim + at detecting and reporting these extra directives. + +*** Precedence warning category + + A new category of warning, -Wprecedence, was introduced. It flags the + useless precedence and associativity directives. + +*** Useless associativity + + Bison now warns about symbols with a declared associativity that is never + used to resolve conflicts. In that case, using %precedence is sufficient; + the parsing tables will remain unchanged. Solving these warnings may raise + useless precedence warnings, as the symbols no longer have associativity. + For example: + + %left '+' + %left '*' + %% + exp: + "number" + | exp '+' "number" + | exp '*' exp + ; + + will produce a + + warning: useless associativity for '+', use %precedence [-Wprecedence] + %left '+' + ^^^ + +*** Useless precedence + + Bison now warns about symbols with a declared precedence and no declared + associativity (i.e., declared with %precedence), and whose precedence is + never used. In that case, the symbol can be safely declared with %token + instead, without modifying the parsing tables. For example: + + %precedence '=' + %% + exp: "var" '=' "number"; + + will produce a + + warning: useless precedence for '=' [-Wprecedence] + %precedence '=' + ^^^ + +*** Useless precedence and associativity + + In case of both useless precedence and associativity, the issue is flagged + as follows: + + %nonassoc '=' + %% + exp: "var" '=' "number"; + + The warning is: + + warning: useless precedence and associativity for '=' [-Wprecedence] + %nonassoc '=' + ^^^ + +** Empty rules + + With help from Joel E. Denny and Gabriel Rassoul. + + Empty rules (i.e., with an empty right-hand side) can now be explicitly + marked by the new %empty directive. Using %empty on a non-empty rule is + an error. The new -Wempty-rule warning reports empty rules without + %empty. On the following grammar: + + %% + s: a b c; + a: ; + b: %empty; + c: 'a' %empty; + + bison reports: + + 3.4-5: warning: empty rule without %empty [-Wempty-rule] + a: {} + ^^ + 5.8-13: error: %empty on non-empty rule + c: 'a' %empty {}; + ^^^^^^ + +** 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". + Contributed by Paolo Bonzini. + +** 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). + +*** %define api.value.type variant + + This is based on a submission from Michiel De Wilde. With help + from Théophile Ranquet. + + In this mode, complex C++ objects can be used as semantic values. For + instance: + + %token <::std::string> TEXT; + %token NUMBER; + %token SEMICOLON ";" + %type <::std::string> item; + %type <::std::list> list; + %% + result: + list { std::cout << $1 << std::endl; } + ; + + list: + %empty { /* Generates an empty string list. */ } + | list item ";" { std::swap ($$, $1); $$.push_back ($2); } + ; + + item: + TEXT { std::swap ($$, $1); } + | NUMBER { $$ = string_cast ($1); } + ; + +*** %define api.token.constructor + + When variants are enabled, Bison can generate functions to build the + tokens. This guarantees that the token type (e.g., NUMBER) is consistent + with the semantic value (e.g., int): + + parser::symbol_type yylex () + { + parser::location_type loc = ...; + ... + return parser::make_TEXT ("Hello, world!", loc); + ... + return parser::make_NUMBER (42, loc); + ... + return parser::make_SEMICOLON (loc); + ... + } + +*** C++ locations + + There are operator- and operator-= for 'location'. Negative line/column + increments can no longer underflow the resulting value. + +* Noteworthy changes in release 2.7.1 (2013-04-15) [stable] + +** Bug fixes + +*** Fix compiler attribute portability (yacc.c) + + With locations enabled, __attribute__ was used unprotected. - When declaring %token A B, the numbering for A is inferior to B. Up to now, - when declaring associativity at the same time, with %left (or %right, - %precedence, %nonassoc), B was inferior to A. +*** Fix some compiler warnings (lalr1.cc) * Noteworthy changes in release 2.7 (2012-12-12) [stable] @@ -346,8 +660,8 @@ GNU Bison NEWS exp: exp '+' exp { $exp = $1 + $3; }; ^^^ - The default behaviour for now is still not to display these unless - explictly asked with -fcaret (or -fall). However, in a later release, it + The default behavior for now is still not to display these unless + explicitly asked with -fcaret (or -fall). However, in a later release, it will be made the default behavior (but may still be deactivated with -fno-caret). @@ -434,7 +748,7 @@ GNU Bison NEWS Other issues in the test suite have been addressed. - Nul characters are correctly displayed in error messages. + Null characters are correctly displayed in error messages. When possible, yylloc is correctly initialized before calling yylex. It is no longer necessary to initialize it in the %initial-action. @@ -2350,7 +2664,12 @@ along with this program. If not, see . 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 Wother nterm arg init - LocalWords: TOK calc yyo fval Wconflicts + LocalWords: TOK calc yyo fval Wconflicts parsers yystackp yyval yynerrs + LocalWords: Théophile Ranquet Santet fno fnone stype associativity Tolmer + LocalWords: Wprecedence Rassoul Wempty Paolo Bonzini parser's Michiel loc + LocalWords: redeclaration sval fcaret reentrant XSLT xsl Wmaybe yyvsp Tedi + LocalWords: pragmas noreturn untyped Rozenman unexpanded Wojciech Polak + LocalWords: Alexandre MERCHANTABILITY yytype Local Variables: mode: outline