Merge remote-tracking branch 'origin/maint'

[bison.git] / NEWS

diff --git a/NEWS b/NEWS
index 3bfc1f94ee1184ecdce6f841977c3aca0a7124bf..d7d89d2a86589bb9dcb73364dcd55da9ce306a25 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -23,6 +23,26 @@ GNU Bison NEWS
   Missing semicolons at the end of actions are no longer added (as announced
   in the release 2.5).
 
   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 (glr.c)
 ** Bug fixes
 
 *** The epilogue is no longer affected by internal #defines (glr.c)


@@ -252,6 +272,78 @@ GNU Bison NEWS
   use these prefixed token names, although the grammar itself still
   uses the short names (as in the sample rule given above).
 
   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 <ival> INT "integer"
+    %token <sval> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <ival>
+    %destructor { free ($$); } <sval>
+
+    /* In yylex().  */
+    yylval.ival = 42; return INT;
+    yylval.sval = "42"; return STRING;
+
+  The %define variable api.value.type supports several special 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> INT "integer"
+    %token <char *> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <int>
+    %destructor { free ($$); } <char *>
+
+    /* 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> INT "integer"
+    %token <std::string> STRING "string"
+
+  Values between 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 <u.ival> INT "integer"
+    %token <u.sval> STRING "string"
+    %printer { fprintf (yyo, "%d", $$); } <u.ival>
+    %destructor { free ($$); } <u.sval>
+
+    /* 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
 ** Variable parse.error
 
   This variable controls the verbosity of error messages.  The use of the


@@ -477,6 +569,16 @@ GNU Bison NEWS
       ...
     }
 
       ...
     }
 

+* Noteworthy changes in release ?.? (????-??-??) [?]
+
+** Bug fixes
+
+*** Fix compiler attribute portability (yacc.c)
+
+  With locations enabled, __attribute__ was used unprotected.
+
+*** Fix some compiler warnings (lalr1.cc)
+

 * Noteworthy changes in release 2.7 (2012-12-12) [stable]
 
 ** Bug fixes
 * Noteworthy changes in release 2.7 (2012-12-12) [stable]
 
 ** Bug fixes


@@ -2536,7 +2638,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
  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:  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
+ LocalWords:  Alexandre MERCHANTABILITY yytype

 
 Local Variables:
 mode: outline
 
 Local Variables:
 mode: outline