Re: Bison scanner patch to fix POSIX incompatibilities, etc.

[Paul Eggert]

> From: Akim Demaille <address@hidden>
> Date: 05 Nov 2002 09:30:47 +0100
> 
> Paul> While we're on the subject of POSIX conformance, I notice that
> Paul> we're not handling C digraphs correctly.  I'll throw that in
> Paul> too; might as well, while I'm at it, since it's easy.
> 
> Really, I see no interest at all in making it that perfect.

I'm a perfectionist so I went ahead and wrote it up anyway.  If it
turns into a problem we can always rip it out.  As a side effect I
noticed that one of the scanner's static variables can easily be made
auto, so I did that too.  I installed this patch.

2002-11-05  Paul Eggert  <address@hidden>

        Scan <% and %> digraphs in C code as POSIX 1003.1-2001 requires.
        Also, remove one static variable in the scanner.

        * src/scan-gram.l (braces_level): Now auto, not static.
        Initialize to zero if the compiler is being picky.
        (INITIAL): Clear braces_level instead of incrementing it.
        (SC_BRACED_CODE): Treat <% and %> as { and } when inside C code,
        as POSIX 1003.1-2001 requires.
        * src/system.h (IF_LINT): New macro, taken from coreutils.
        * configure.ac: Define "lint" if --enable-gcc-warnings.

Index: src/scan-gram.l
===================================================================
RCS file: /cvsroot/bison/bison/src/scan-gram.l,v
retrieving revision 1.32
retrieving revision 1.33
diff -p -u -r1.32 -r1.33
--- src/scan-gram.l     5 Nov 2002 21:20:14 -0000       1.32
+++ src/scan-gram.l     5 Nov 2002 23:50:11 -0000       1.33
@@ -163,7 +163,6 @@ scanner_last_string_free (void)
 }
 
 
-static int braces_level = 0;
 static int percent_percent_count = 0;
 
 /* Within well-formed rules, RULE_LENGTH is the number of values in
@@ -202,6 +201,8 @@ splice       (\\[ \f\t\v]*\n)*
 
 %%
 %{
+  int braces_level IF_LINT (= 0);
+
   /* At each yylex invocation, mark the current position as the
      start of the next token.  */
   YY_STEP;
@@ -294,7 +295,7 @@ splice       (\\[ \f\t\v]*\n)*
   "%{"        yy_push_state (SC_PROLOGUE);
 
   /* Code in between braces.  */
-  "{"         YY_OBS_GROW; ++braces_level; yy_push_state (SC_BRACED_CODE);
+  "{"         YY_OBS_GROW; braces_level = 0; yy_push_state (SC_BRACED_CODE);
 
   /* A type. */
   "<"{tag}">" {
@@ -583,9 +584,12 @@ splice      (\\[ \f\t\v]*\n)*
 
 <SC_BRACED_CODE>
 {
+  "{"|"<"{splice}"%"  YY_OBS_GROW; braces_level++;
+  "%"{splice}">"      YY_OBS_GROW; braces_level--;
   "}" {
     YY_OBS_GROW;
-    if (--braces_level == 0)
+    braces_level--;
+    if (braces_level < 0)
       {
        yy_pop_state ();
        YY_OBS_FINISH;
@@ -595,17 +599,14 @@ splice     (\\[ \f\t\v]*\n)*
       }
   }
 
-  "{"                  YY_OBS_GROW; braces_level++;
-
   "$"("<"{tag}">")?(-?[0-9]+|"$") { handle_dollar (current_braced_code,
                                                   yytext, *yylloc); }
   "@"(-?[0-9]+|"$")               { handle_at (current_braced_code,
                                               yytext, *yylloc); }
 
-  address@hidden/\'\"\{\}]+    YY_OBS_GROW;
-
-  /* A stray $, or /, or etc. */
-  .             YY_OBS_GROW;
+  /* `"<"{splice}"<"' tokenizes `<<%' correctly (as `<<' `%') rather
+     than incorrrectly (as `<' `<%').  */
+  [^\"$%\'/<@\[\]\{\}]+|[$%/<@]|"<"{splice}"<"  YY_OBS_GROW;
 
   <<EOF>> {
     complain_at (*yylloc, _("unexpected end of file in a braced code"));
Index: src/system.h
===================================================================
RCS file: /cvsroot/bison/bison/src/system.h,v
retrieving revision 1.54
retrieving revision 1.55
diff -p -u -r1.54 -r1.55
--- src/system.h        3 Nov 2002 06:16:55 -0000       1.54
+++ src/system.h        5 Nov 2002 23:42:51 -0000       1.55
@@ -129,6 +129,14 @@ void *memrchr (const void *s, int c, siz
 | GCC extensions.  |
 `-----------------*/
 
+/* Use this to suppress gcc's `...may be used before initialized'
+   warnings.  */
+#ifdef lint
+# define IF_LINT(Code) Code
+#else
+# define IF_LINT(Code) /* empty */
+#endif
+
 #ifndef __attribute__
 /* This feature is available in gcc versions 2.5 and later.  */
 # if !defined (__GNUC__) || __GNUC__ < 2 || \
Index: configure.ac
===================================================================
RCS file: /cvsroot/bison/bison/configure.ac,v
retrieving revision 1.20
retrieving revision 1.21
diff -p -u -r1.20 -r1.21
--- configure.ac        3 Nov 2002 08:39:16 -0000       1.20
+++ configure.ac        5 Nov 2002 23:42:10 -0000       1.21
@@ -56,6 +56,7 @@ if test "${enableval}" = yes; then
   BISON_WARNING(-Wshadow)
   BISON_WARNING(-Wstrict-prototypes)
   BISON_WARNING(-Wwrite-strings)
+  AC_DEFINE([lint], 1, [Define to 1 if the compiler is checking for lint.])
 fi
 
 # Checks for programs.