X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/c21e515e05224b7898e8603f2b4142df42f138a7..90b89dadb24edfe00ed163ddb9407a48d6f4a9ac:/NEWS?ds=inline diff --git a/NEWS b/NEWS index 5b9a6e80..3816fdd5 100644 --- a/NEWS +++ b/NEWS @@ -4,14 +4,6 @@ GNU Bison NEWS ** WARNING: Future backward-incompatibilities! - Bison will stop adding a semicolon at the end of the actions (as announced - in the release 2.5): - - 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 ';' - Like other GNU packages, Bison will start using some of the C99 features for its own code, especially the definition of variables after statements. The generated C parsers still aim at C90. @@ -28,6 +20,9 @@ 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). + ** Bug fixes *** The epilogue is no longer affected by internal #defines (glr.c) @@ -39,7 +34,7 @@ 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) @@ -58,6 +53,29 @@ 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 +216,11 @@ 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 @@ -229,6 +252,77 @@ 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 ($$); } + + /* In yylex(). */ + yylval.ival = 42; return INT; + yylval.sval = "42"; return STRING; + + The %define variable api.value.type supports several special values. The + value "union" means that the user provides genuine types, not union member + names such as "ival" and "sval" above. + + %define api.value.type "union" + %token INT "integer" + %token STRING "string" + %printer { fprintf (yyo, "%d", $$); } + %destructor { free ($$); } + + /* In yylex(). */ + yylval.INT = 42; return INT; + yylval.STRING = "42"; return STRING; + + The value "variant" is somewhat equivalent, but for C++ special provision + is made to allow classes to be used (more about this below). + + %define api.value.type "variant" + %token INT "integer" + %token STRING "string" + + Any other name is a user type to use. This is where YYSTYPE used to be + used. + + %code requires + { + struct my_value + { + enum + { + is_int, is_string + } kind; + union + { + int ival; + char *sval; + } u; + }; + } + %define api.value.type "struct my_value" + %token INT "integer" + %token STRING "string" + %printer { fprintf (yyo, "%d", $$); } + %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 @@ -261,17 +355,33 @@ 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' - 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. + 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 developping and maintaining a grammar, useless associativity and + 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 @@ -296,8 +406,8 @@ GNU Bison NEWS %left '*' %% exp: - "num" - | exp '+' "num" + "number" + | exp '+' "number" | exp '*' exp ; @@ -316,7 +426,7 @@ GNU Bison NEWS %precedence '=' %% - exp: "var" '=' "num"; + exp: "var" '=' "number"; will produce a @@ -331,7 +441,7 @@ GNU Bison NEWS %nonassoc '=' %% - exp: "var" '=' "num"; + exp: "var" '=' "number"; The warning is: @@ -339,6 +449,30 @@ GNU Bison NEWS %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 Contributed by Paolo Bonzini. @@ -387,7 +521,7 @@ GNU Bison NEWS ; list: - /* nothing */ { /* Generates an empty string list */ } + %empty { /* Generates an empty string list. */ } | list item ";" { std::swap ($$, $1); $$.push_back ($2); } ; @@ -464,8 +598,8 @@ 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). @@ -552,7 +686,7 @@ 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. @@ -2468,7 +2602,12 @@ 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