proposed Bison patch for YYDEBUG for POSIX compliance

[Paul Eggert]

Here's a proposed patch to fix one or two POSIX-compliance bugs in Bison.

* POSIX says that YYDEBUG must be defined to be 0 if the user never specifies
  debugging, but the Bison-generated parser leaves YYDEBUG undefined.

* This is a very minor point, but POSIX doesn't seem to require that
  the user must YYDEBUG to a parenthesized expression, e.g. `#define
  YYDEBUG 0 ? 0 : 1' seems to be allowed.  We might as well survive
  such programs while we're at it.


Index: ChangeLog
===================================================================
RCS file: /cvsroot/bison/bison/ChangeLog,v
retrieving revision 1.173.2.229
diff -p -u -r1.173.2.229 ChangeLog
--- ChangeLog   13 Dec 2001 11:14:19 -0000      1.173.2.229
+++ ChangeLog   15 Dec 2001 02:20:56 -0000
@@ -1,3 +1,12 @@
+2001-12-14  Paul Eggert  <address@hidden>
+
+       * src/output.c (output): Define YYDEBUG to 0 if it is not defined
+       and if we are not debugging.
+       * NEWS, doc/bison.texinfo, doc/bison.1, doc/bison.rnh: Document this.
+
+       * src/output.c (output_gram, output_rule_data): Do not assume that
+       the user defines YYDEBUG to a properly parenthesized expression.
+
 2001-12-13  Akim Demaille  <address@hidden>
 
        Version 1.30g.
Index: NEWS
===================================================================
RCS file: /cvsroot/bison/bison/NEWS,v
retrieving revision 1.21.2.36
diff -p -u -r1.21.2.36 NEWS
--- NEWS        13 Dec 2001 12:07:47 -0000      1.21.2.36
+++ NEWS        15 Dec 2001 02:20:56 -0000
@@ -3,6 +3,9 @@ Bison News
 
 Changes in version 1.30h:
 
+* When the generated parser lacks debugging code, YYDEBUG is now 0 instead
+  undefined, as POSIX requires.
+
 Changes in version 1.30g:
 
 * Bug fixes
cvs server: Diffing config
cvs server: Diffing doc
Index: doc/bison.1
===================================================================
RCS file: /cvsroot/bison/bison/doc/bison.1,v
retrieving revision 1.7.2.3
diff -p -u -r1.7.2.3 bison.1
--- doc/bison.1 19 Sep 2001 13:09:32 -0000      1.7.2.3
+++ doc/bison.1 15 Dec 2001 02:20:56 -0000
@@ -262,9 +262,9 @@ and so on.
 .ns
 .TP
 .B \-\-debug
-Output a definition of the macro
+In the parser file, define the macro
 .B YYDEBUG
-into the parser file,
+to 1 if it is not already defined,
 so that the debugging facilities are compiled.
 .TP
 .B \-v
Index: doc/bison.rnh
===================================================================
RCS file: /cvsroot/bison/bison/doc/bison.rnh,v
retrieving revision 1.2
diff -p -u -r1.2 bison.rnh
--- doc/bison.rnh       16 Oct 1995 14:11:03 -0000      1.2
+++ doc/bison.rnh       15 Dec 2001 02:20:56 -0000
@@ -56,7 +56,8 @@ foo_tab.c.
 .indent -1
 2 /DEBUG
 .skip
-Output a definition of the macro YYDEBUG into the parser file,
+In the parser file,
+define the macro YYDEBUG to 1 if it is not already defined,
 so that the debugging facilities are compiled.
 .skip
 .indent -1
Index: doc/bison.texinfo
===================================================================
RCS file: /cvsroot/bison/bison/doc/bison.texinfo,v
retrieving revision 1.37.2.12
diff -p -u -r1.37.2.12 bison.texinfo
--- doc/bison.texinfo   13 Dec 2001 02:45:14 -0000      1.37.2.12
+++ doc/bison.texinfo   15 Dec 2001 02:20:58 -0000
@@ -708,8 +708,8 @@ headers.  On some address@hidden hosts, @c
 @code{<stddef.h>}, and @code{<stdlib.h>} are included as needed to
 declare memory allocators and related types.  In the same situation,
 C++ parsers may include @code{<cstddef>} and @code{<cstdlib>} instead.
-Other system headers may be included if you define @code{YYDEBUG}
-(@pxref{Debugging, ,Debugging Your Parser}).
+Other system headers may be included if you define @code{YYDEBUG} to a
+nonzero value (@pxref{Debugging, ,Debugging Your Parser}).
 
 @node Stages
 @section Stages in Using Bison
@@ -3235,9 +3235,9 @@ directives:
 
 @table @code
 @item %debug
-Output a definition of the macro @code{YYDEBUG} into the parser file, so
-that the debugging facilities are compiled.  @xref{Debugging, ,Debugging
-Your Parser}.
+In the parser file, define the macro @code{YYDEBUG} to 1 if it is not
+already defined, so that the debugging facilities are compiled.
address@hidden, ,Debugging Your Parser}.
 
 @item %defines
 Write an extra output file containing macro definitions for the token
@@ -4925,21 +4925,23 @@ If a Bison grammar compiles properly but
 runs, the @code{yydebug} parser-trace feature can help you figure out why.
 
 To enable compilation of trace facilities, you must define the macro
address@hidden when you compile the parser.  You could use
address@hidden as a compiler option or you could put @samp{#define
-YYDEBUG 1} in the C declarations section of the grammar file
-(@pxref{C Declarations, ,The C Declarations Section}).  Alternatively, use the 
@samp{-t} option when
-you run Bison (@pxref{Invocation, ,Invoking Bison}).  We always define 
@code{YYDEBUG} so that
-debugging is always possible.
address@hidden to a nonzero value when you compile the parser.  You
+could use @samp{-DYYDEBUG=1} as a compiler option or you could put
address@hidden YYDEBUG 1} in the C declarations section of the grammar
+file (@pxref{C Declarations, ,The C Declarations Section}).
+Alternatively, use the @samp{-t} option when you run Bison
+(@pxref{Invocation, ,Invoking Bison}) or the @code{%debug} declaration
+(@pxref{Decl Summary, ,Bison Declaration Summary}).  We suggest that
+you always define @code{YYDEBUG} so that debugging is always possible.
 
 The trace facility outputs messages with macro calls of the form
 @code{YYFPRINTF (YYSTDERR, @var{format}, @var{args})} where
 @var{format} and @var{args} are the usual @code{printf} format and
-arguments.  If you define @code{YYDEBUG} but do not define
address@hidden, @code{<stdio.h>} is automatically included and the
-macros are defined to @code{fprintf} and @code{stderr}.  In the same
-situation, C++ parsers include @code{<cstdio.h>} instead, and use
address@hidden::fprintf} and @code{std::stderr}.
+arguments.  If you define @code{YYDEBUG} to a nonzero value but do not
+define @code{YYFPRINTF}, @code{<stdio.h>} is automatically included
+and the macros are defined to @code{fprintf} and @code{stderr}.  In
+the same situation, C++ parsers include @code{<cstdio.h>} instead, and
+use @code{std::fprintf} and @code{std::stderr}.
 
 Once you have compiled the program with trace facilities, the way to
 request a trace is to store a nonzero value in the variable @code{yydebug}.
@@ -5100,9 +5102,9 @@ you are developing Bison.
 
 @item -t
 @itemx --debug
-Output a definition of the macro @code{YYDEBUG} into the parser file, so
-that the debugging facilities are compiled.  @xref{Debugging, ,Debugging
-Your Parser}.
+In the parser file, define the macro @code{YYDEBUG} to 1 if it is not
+already defined, so that the debugging facilities are compiled.
address@hidden, ,Debugging Your Parser}.
 
 @item --locations
 Pretend that @code{%locations} was specified.  @xref{Decl Summary}.
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Index: src/output.c
===================================================================
RCS file: /cvsroot/bison/bison/src/output.c,v
retrieving revision 1.39.2.18
diff -p -u -r1.39.2.18 output.c
--- src/output.c        13 Dec 2001 02:21:12 -0000      1.39.2.18
+++ src/output.c        15 Dec 2001 02:20:58 -0000
@@ -316,7 +316,7 @@ output_gram (void)
      yyprhs and yyrhs are needed only for yydebug. */
   /* With the no_parser option, all tables are generated */
   if (!semantic_parser && !no_parser_flag)
-    obstack_sgrow (&table_obstack, "\n#if YYDEBUG != 0\n");
+    obstack_sgrow (&table_obstack, "\n#if YYDEBUG\n");
 
   {
     int i;
@@ -372,7 +372,7 @@ output_rule_data (void)
   short *short_tab = NULL;
 
   obstack_sgrow (&table_obstack, "\n\
-#if YYDEBUG != 0\n");
+#if YYDEBUG\n");
 
   {
     short *values = XCALLOC (short, nrules + 1);
@@ -400,7 +400,7 @@ output_rule_data (void)
   /* Output the table of symbol names.  */
   if (!token_table_flag && !no_parser_flag)
     obstack_sgrow (&table_obstack,
-                        "\n#if YYDEBUG != 0 || defined YYERROR_VERBOSE\n\n");
+                        "\n#if (YYDEBUG) || defined YYERROR_VERBOSE\n\n");
   obstack_sgrow (&table_obstack, "\
 /* YYTNAME[TOKEN_NUM] -- String name of the token TOKEN_NUM. */\n");
   obstack_sgrow (&table_obstack,
@@ -1268,12 +1268,11 @@ output (void)
       obstack_grow (&table_obstack, obstack_finish (&attrs_obstack), size);
     }
   reader_output_yylsp (&table_obstack);
-  if (debug_flag)
-    obstack_sgrow (&table_obstack, "\
+  obstack_fgrow1 (&table_obstack, "\
 #ifndef YYDEBUG\n\
-# define YYDEBUG 1\n\
+# define YYDEBUG %d\n\
 #endif\n\
-\n");
+\n", debug_flag);
 
   if (semantic_parser)
     obstack_fgrow1 (&table_obstack, "#include %s\n",
cvs server: Diffing tests