FYI: Both: Protect YYSTYPE

[Akim Demaille]

I think it'd be cool if the header could always be included in the
parser.

I realized a few shortcomings with the current headers: for instance
we don't define yydebug, nor yypatch etc.  We should IMHO.  Also, the
support for --prefix-name is lacking.  But we can't just issue some
#define yyparse fooparse, because that is still a global definition of
yyparse.  We really need to issue a proto of fooparse.

This is to be addressed in the trunk.

Index: ChangeLog
from  Akim Demaille  <address@hidden>

        * src/reader.c (parse_union_decl): Output yystype/YYSTYPE as we do
        with yyltype/YYLTYPE.  This allows inclusion of the generated
        header within the parser if the compiler, such as GGC, accepts
        multiple equivalent #defines.

Index: doc/bison.texinfo
--- doc/bison.texinfo Sun, 04 Nov 2001 17:13:49 +0100 akim
+++ doc/bison.texinfo Sun, 04 Nov 2001 20:13:25 +0100 akim
@@ -855,11 +855,12 @@ @node Rpcalc Decls
 preprocessor directives.

 The @code{#define} directive defines the macro @code{YYSTYPE}, thus
-specifying the C data type for semantic values of both tokens and groupings
-(@pxref{Value Type, ,Data Types of Semantic Values}).  The Bison parser will 
use whatever type
address@hidden is defined as; if you don't define it, @code{int} is the
-default.  Because we specify @code{double}, each token and each expression
-has an associated value, which is a floating point number.
+specifying the C data type for semantic values of both tokens and
+groupings (@pxref{Value Type, ,Data Types of Semantic Values}).  The
+Bison parser will use whatever type @code{YYSTYPE} is defined as; if you
+don't define it, @code{int} is the default.  Because we specify
address@hidden, each token and each expression has an associated value,
+which is a floating point number.

 The @code{#include} directive is used to declare the exponentiation
 function @code{pow}.
@@ -1066,10 +1067,11 @@ @node Rpcalc Lexer
 macro whose definition is the appropriate number.  In this example,
 therefore, @code{NUM} becomes a macro for @code{yylex} to use.

-The semantic value of the token (if it has one) is stored into the global
-variable @code{yylval}, which is where the Bison parser will look for it.
-(The C data type of @code{yylval} is @code{YYSTYPE}, which was defined
-at the beginning of the grammar; @pxref{Rpcalc Decls, ,Declarations for 
@code{rpcalc}}.)
+The semantic value of the token (if it has one) is stored into the
+global variable @code{yylval}, which is where the Bison parser will look
+for it.  (The C data type of @code{yylval} is @code{YYSTYPE}, which was
+defined at the beginning of the grammar; @pxref{Rpcalc Decls,
+,Declarations for @code{rpcalc}}.)

 A token type code of zero is returned if the end-of-file is encountered.
 (Bison recognizes any nonpositive value as indicating the end of the
@@ -2374,7 +2376,8 @@ @node Value Type

 In a simple program it may be sufficient to use the same data type for
 the semantic values of all language constructs.  This was true in the
-RPN and infix calculator examples (@pxref{RPN Calc, ,Reverse Polish Notation 
Calculator}).
+RPN and infix calculator examples (@pxref{RPN Calc, ,Reverse Polish
+Notation Calculator}).

 Bison's default is to use type @code{int} for all semantic values.  To
 specify some other type, define @code{YYSTYPE} as a macro, like this:
Index: src/reader.c
--- src/reader.c Sun, 04 Nov 2001 17:13:49 +0100 akim
+++ src/reader.c Sun, 04 Nov 2001 20:35:07 +0100 akim
@@ -711,6 +711,13 @@
 {
   int c;
   int count = 0;
+  const char *prologue = "\
+#ifndef YYSTYPE\n\
+typedef union";
+  const char *epilogue = "\
+ yystype;\n\
+# define YYSTYPE yystype\n\
+#endif\n";

   if (typed)
     complain (_("multiple %s declarations"), "%union");
@@ -723,9 +730,9 @@
   else
     obstack_1grow (&attrs_obstack, '\n');

-  obstack_sgrow (&attrs_obstack, "typedef union");
+  obstack_sgrow (&attrs_obstack, prologue);
   if (defines_flag)
-    obstack_sgrow (&defines_obstack, "typedef union");
+    obstack_sgrow (&defines_obstack, prologue);

   c = getc (finput);

@@ -760,9 +767,9 @@
          count--;
          if (count <= 0)
            {
-             obstack_sgrow (&attrs_obstack, " YYSTYPE;\n");
+             obstack_sgrow (&attrs_obstack, epilogue);
              if (defines_flag)
-               obstack_sgrow (&defines_obstack, " YYSTYPE;\n");
+               obstack_sgrow (&defines_obstack, epilogue);
              /* JF don't choke on trailing semi */
              c = skip_white_space ();
              if (c != ';')
@@ -1955,7 +1962,6 @@
   /* Read the declaration section.  Copy %{ ... %} groups to
      TABLE_OBSTACK and FDEFINES file.  Also notice any %token, %left,
      etc. found there.  */
-  obstack_1grow (&table_obstack, '\n');
   obstack_fgrow3 (&table_obstack, "\
 /* %s, made from %s\n\
    by GNU bison %s.  */\n\