Re: YYSTYPE_IS_TRIVIAL

[Paul Eggert]

> From: Akim Demaille <address@hidden>
> Date: 22 Apr 2002 15:42:12 +0200
> 
> I think the patch should be applied to the head too, but of course we
> can debate about it.  If you too think we should apply it, would you
> do it?  I'm fine with tweaking it a bit afterwards if needed, and I'm
> fine with helping you too.

OK, here's my first cut at trying to adapt the patches in:
http://mail.gnu.org/pipermail/bison-patches/2002-March/000760.html

The main problem is that I haven't a clue as to what to do about those
patches to reader.c.  I gather that I need to add a muscle, but I need
something that will define YYSTYPE_IS_TRIVIAL only if the user does
not define YYSTYPE.  In 1_29-branch I did this:

     const char *prologue = "\
   #ifndef YYSTYPE\n\
   typedef union";
     const char *epilogue = "\
    yystype;\n\
   # define YYSTYPE yystype\n\
   # define YYSTYPE_IS_TRIVIAL 1\n\
   #endif\n";
     ...
     obstack_sgrow (&attrs_obstack, prologue);
     [copy some stuff to attrs_obstack]
     obstack_sgrow (&attrs_obstack, epilogue);
  
but I don't see how to get the same effect using muscles.

I can merge the bison.simple part of the patch, as follows, and I
think the following patch is an improvement (though I can't test this
easily as the head has problems on my host as I discussed in an
earlier message today).  However, by itself the patch below won't fix
the C++-compiler-masquerading-as-C-compiler problem on the head.

2002-04-22  Paul Eggert  <address@hidden>

        * data/bison.simple: Remove unnecessary commentary and white
        space differences from 1_29-branch.
        
        (union yyalloc, YYSTACK_GAP_MAX, YYSTACK_BYTES, YYCOPY,
        YYSTACK_RELOCATE): Do not define if yyoverflow is defined, or
        if this is a C++ parser and YYSTYPE or YYLTYPE has nontrivial
        constructors or destructors.

        (yyparse) [! defined YYSTACK_RELOCATE]: Do not relocate the stack.

--- bison.simple.~1.12.~        2002-04-22 01:22:22.000000000 -0700
+++ bison.simple        2002-04-22 12:09:36.627402000 -0700
@@ -89,6 +89,13 @@ m4_divert(0)dnl
    It was written by Richard Stallman by simplifying the hairy parser
    used when %semantic_parser is specified.  */
 
+/* All symbols defined below should begin with yy or YY, to avoid
+   infringing on user name space.  This should be done even for local
+   variables, as they might otherwise be expanded by user macros.
+   There are some unavoidable exceptions within include files to
+   define necessary library symbols; they are noted "INFRINGES ON
+   USER NAME SPACE" below.  */
+
 /* Identify Bison output.  */
 #define YYBISON        1
 
@@ -151,14 +158,7 @@ typedef struct yyltype
 /* Line __line__ of __file__.  */
 #line __oline__ "__ofile__"
 
-/* All symbols defined below should begin with yy or YY, to avoid
-   infringing on user name space.  This should be done even for local
-   variables, as they might otherwise be expanded by user macros.
-   There are some unavoidable exceptions within include files to
-   define necessary library symbols; they are noted "INFRINGES ON
-   USER NAME SPACE" below.  */
-
-#if ! defined (yyoverflow) || defined (YYERROR_VERBOSE)
+#if ! defined (yyoverflow) || YYERROR_VERBOSE
 
 /* The parser invokes alloca or malloc; define the necessary symbols.  */
 
@@ -187,6 +187,12 @@ typedef struct yyltype
 #  define YYSTACK_ALLOC malloc
 #  define YYSTACK_FREE free
 # endif
+#endif /* ! defined (yyoverflow) || YYERROR_VERBOSE */
+
+
+#if (! defined (yyoverflow) \
+     && (! defined (__cplusplus) \
+        || (YYLTYPE_IS_TRIVIAL && YYSTYPE_IS_TRIVIAL)))
 
 /* A type that is properly aligned for any stack member.  */
 union yyalloc
@@ -205,12 +211,12 @@ union yyalloc
    N elements.  */
 # if YYLSP_NEEDED
 #  define YYSTACK_BYTES(N) \
-    ((N) * (sizeof (short) + sizeof (YYSTYPE) + sizeof (YYLTYPE))      \
-     + 2 * YYSTACK_GAP_MAX)
+     ((N) * (sizeof (short) + sizeof (YYSTYPE) + sizeof (YYLTYPE))     \
+      + 2 * YYSTACK_GAP_MAX)
 # else
 #  define YYSTACK_BYTES(N) \
-    ((N) * (sizeof (short) + sizeof (YYSTYPE))                         \
-     + YYSTACK_GAP_MAX)
+     ((N) * (sizeof (short) + sizeof (YYSTYPE))                                
\
+      + YYSTACK_GAP_MAX)
 # endif
 
 /* Copy COUNT objects from FROM to TO.  The source and destination do
@@ -247,7 +253,7 @@ union yyalloc
       }                                                                        
\
     while (0)
 
-#endif /* ! defined (yyoverflow) || YYERROR_VERBOSE */
+#endif
 
 /* Tokens.  */
 b4_token_defines(b4_tokens)
@@ -469,8 +475,8 @@ do {                                                \
   if (yydebug)                                 \
     YYFPRINTF Args;                            \
 } while (0)
-/* Nonzero means print parse trace.  Since this is uninitialized, it
-   does not stop multiple parsers from coexisting.  */
+/* Nonzero means print parse trace.  It is left uninitialized so that
+   multiple parsers can coexist.  */
 int yydebug;
 #else /* !YYDEBUG */
 # define YYDPRINTF(Args)
@@ -738,6 +744,9 @@ yyparse (YYPARSE_PARAM_ARG)
        yyvs = yyvs1;
       }
 #else /* no yyoverflow */
+# ifndef YYSTACK_RELOCATE
+      goto yyoverflowlab;
+# else
       /* Extend the stack our own way.  */
       if (yystacksize >= YYMAXDEPTH)
        goto yyoverflowlab;
@@ -753,13 +762,14 @@ yyparse (YYPARSE_PARAM_ARG)
          goto yyoverflowlab;
        YYSTACK_RELOCATE (yyss);
        YYSTACK_RELOCATE (yyvs);
-# if YYLSP_NEEDED
+#  if YYLSP_NEEDED
        YYSTACK_RELOCATE (yyls);
-# endif
-# undef YYSTACK_RELOCATE
+#  endif
+#  undef YYSTACK_RELOCATE
        if (yyss1 != yyssa)
          YYSTACK_FREE (yyss1);
       }
+# endif
 #endif /* no yyoverflow */
 
       yyssp = yyss + yysize - 1;
@@ -1058,7 +1068,7 @@ yyerrlab1:
   /* Else will try to reuse lookahead token after shifting the error
      token.  */
 
-  yyerrstatus = 3;             /* Each real token shifted decrements this.  */
+  yyerrstatus = 3;     /* Each real token shifted decrements this.  */
 
   goto yyerrhandle;