X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/18ad57b384e164c337e735df2f0ed0fe3c51fbf5..297e263a0050959e0fd139ad66e71383fc9ac4db:/NEWS

diff --git a/NEWS b/NEWS
index 72e4b6b3..41e68519 100644
--- a/NEWS
+++ b/NEWS
@@ -2,19 +2,144 @@ GNU Bison NEWS
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
-** Future changes:
+** Warnings about 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 <type1> term
+    %type  <type2> nterm
+    %printer    {} <type1> <type3>
+    %destructor {} <type2> <type4>
+    %%
+    nterm: term { $$ = $1; };
+
+    3.28-34: warning: type <type3> is used, but is not associated to any symbol
+    4.28-34: warning: type <type4> is used, but is not associated to any symbol
+
+** Warnings about undeclared symbols
+
+  Bison used to raise an error for %printer and %destructor directives for
+  undefined symbols.
+
+    %printer    {} symbol1
+    %destructor {} symbol2
+    %%
+    exp: "a";
+
+  This is now only a warning.
+
+** Warnings about useless destructors or printers
+
+  Bison now warns about useless destructors or printers.  In the following
+  example, the printer for <type1>, and the destructor for <type2> are
+  useless: all symbols of <type1> (token1) already have a printer, and all
+  symbols of type <type2> (token2) already have a destructor.
+
+    %token <type1> token1
+           <type2> token2
+           <type3> token3
+           <type4> token4
+    %printer    {} token1 <type1> <type3>
+    %destructor {} token2 <type2> <type4>
+
+** 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++ skeleton improvements
+
+  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).
+
+** Variable api.tokens.prefix
+
+  The variable api.tokens.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_"
+    %%
+    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 api.namespace
+
+  The "namespace" variable is renamed "api.namespace".  Backward
+  compatibility is ensured, but upgrading is recommended.
+
+** 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".
+
+** 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
+  runtime expressions.
+
+* Noteworthy changes in release ?.? (????-??-??) [?]
+
+** 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
+
+  Support for generating parsers in K&R C will be removed.  Parsers
+  generated for C supprt ISO C90, and are tested with ISO C99 and ISO C11
+  compilers.
+
+*** Deprecated features
+
+  The definitions of yystype and yyltype will be removed, as announced since
+  Bison 1.875.  Use YYSTYPE and YYLTYPE only.
 
-  The next major release will drop support for generating parsers in K&R C,
-  and remove the definitions of yystype and yyltype (removal announced since
-  Bison 1.875).  YYPARSE_PARAM and YYLEX_PARAM, which were deprecated in
-  favor of %parse-param and %lex-param (introduced in Bison 1.875 too), will
-  no longer be supported.
+  YYPARSE_PARAM and YYLEX_PARAM, which were deprecated in favor of
+  %parse-param and %lex-param (introduced in Bison 1.875), will no longer be
+  supported.
 
-** The generated header is included (yacc.c)
+*** The generated header will be included (yacc.c)
 
   Instead of duplicating the content of the generated header (definition of
-  YYSTYPE, yyltype etc.), the generated parser now includes it, as was
-  already the case for GLR or C++ parsers.
+  YYSTYPE, yyparse declaration etc.), the generated parser will include it,
+  as is already the case for GLR or C++ parsers.  This change is deferred
+  because existing versions of ylwrap (e.g., Automake 1.12.1) do not support
+  it.
 
 ** Headers (yacc.c, glr.c, glr.cc)