** 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.
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)
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)
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
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
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
%left '*'
%%
exp:
- "num"
- | exp '+' "num"
+ "number"
+ | exp '+' "number"
| exp '*' exp
;
%precedence '='
%%
- exp: "var" '=' "num";
+ exp: "var" '=' "number";
will produce a
%nonassoc '='
%%
- exp: "var" '=' "num";
+ exp: "var" '=' "number";
The warning is:
%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.
;
list:
- /* nothing */ { /* Generates an empty string list */ }
+ %empty { /* Generates an empty string list. */ }
| list item ";" { std::swap ($$, $1); $$.push_back ($2); }
;
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).
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.
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
Local Variables:
mode: outline
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