Re: yacc.c: Extracting yysyntax_error

[Paul Eggert]

I installed the following patch in the hope of addressing the issues
involved.  I couldn't make it quite as clean as the glr.c version due
to backward compatibility issues with alloca.

2005-09-19  Paul Eggert  <address@hidden>

        * data/yacc.c (YYSIZE_MAXIMUM): New macro.
        (YYSTACK_ALLOC_MAXIMUM): Use it.
        (yysyntax_error): New function.
        (yyparse) [YYERROR_VERBOSE]: Don't leak memory indefinitely if
        multiple syntax errors are reported, and alloca is being used.
        Instead, reallocate buffers twice as big each time, so that
        we waste at most half the allocated memory.  Start with a small
        (128-byte) buffer that will suffice in most cases anyway.
        Use yysyntax_error to do most of the work.

Index: yacc.c
===================================================================
RCS file: /cvsroot/bison/bison/data/yacc.c,v
retrieving revision 1.104
retrieving revision 1.105
diff -p -u -r1.104 -r1.105
--- yacc.c      16 Sep 2005 19:03:54 -0000      1.104
+++ yacc.c      20 Sep 2005 06:06:42 -0000      1.105
@@ -233,6 +233,8 @@ b4_syncline(address@hidden@], address@hidden@])[
 # define YYSIZE_T unsigned int
 #endif
 
+#define YYSIZE_MAXIMUM ((YYSIZE_T) -1)
+
 #ifndef YY_
 # if YYENABLE_NLS
 #  if ENABLE_NLS
@@ -277,7 +279,7 @@ b4_syncline(address@hidden@], address@hidden@])[
 #  define YYSTACK_ALLOC YYMALLOC
 #  define YYSTACK_FREE YYFREE
 #  ifndef YYSTACK_ALLOC_MAXIMUM
-#   define YYSTACK_ALLOC_MAXIMUM ((YYSIZE_T) -1)
+#   define YYSTACK_ALLOC_MAXIMUM YYSIZE_MAXIMUM
 #  endif
 #  ifdef __cplusplus
 extern "C" {
@@ -788,8 +790,114 @@ yytnamerr (char *yyres, const char *yyst
 }
 # endif
 
-#endif /* YYERROR_VERBOSE */
+/* Copy into YYRESULT an error message about the unexpected token
+   YYCHAR while in state YYSTATE.  Return the number of bytes copied,
+   including the terminating null byte.  If YYRESULT is null, do not
+   copy anything; just return the number of bytes that would be
+   copied.  As a special case, return 0 if an ordinary "syntax error"
+   message will do.  Return YYSIZE_MAXIMUM if overflow occurs during
+   size calculation.  */
+static YYSIZE_T
+yysyntax_error (char *yyresult, int yystate, int yychar)
+{
+  int yyn = yypact[yystate];
 
+  if (! (YYPACT_NINF < yyn && yyn < YYLAST))
+    return 0;
+  else
+    {
+      int yytype = YYTRANSLATE (yychar);
+      YYSIZE_T yysize0 = yytnamerr (0, yytname[yytype]);
+      YYSIZE_T yysize = yysize0;
+      YYSIZE_T yysize1;
+      int yysize_overflow = 0;
+      enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
+      char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
+      int yyx;
+
+# if 0
+      /* This is so xgettext sees the translatable formats that are
+         constructed on the fly.  */
+      YY_("syntax error, unexpected %s");
+      YY_("syntax error, unexpected %s, expecting %s");
+      YY_("syntax error, unexpected %s, expecting %s or %s");
+      YY_("syntax error, unexpected %s, expecting %s or %s or %s");
+      YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s");
+# endif
+      char *yyfmt;
+      char const *yyf;
+      static char const yyunexpected[] = "syntax error, unexpected %s";
+      static char const yyexpecting[] = ", expecting %s";
+      static char const yyor[] = " or %s";
+      char yyformat[sizeof yyunexpected
+                    + sizeof yyexpecting - 1
+                    + ((YYERROR_VERBOSE_ARGS_MAXIMUM - 2)
+                       * (sizeof yyor - 1))];
+      char const *yyprefix = yyexpecting;
+
+      /* Start YYX at -YYN if negative to avoid negative indexes in
+         YYCHECK.  */
+      int yyxbegin = yyn < 0 ? -yyn : 0;
+
+      /* Stay within bounds of both yycheck and yytname.  */
+      int yychecklim = YYLAST - yyn;
+      int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
+      int yycount = 1;
+
+      yyarg[0] = yytname[yytype];
+      yyfmt = yystpcpy (yyformat, yyunexpected);
+
+      for (yyx = yyxbegin; yyx < yyxend; ++yyx)
+        if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR)
+          {
+            if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
+              {
+                yycount = 1;
+                yysize = yysize0;
+                yyformat[sizeof yyunexpected - 1] = '\0';
+                break;
+              }
+            yyarg[yycount++] = yytname[yyx];
+            yysize1 = yysize + yytnamerr (0, yytname[yyx]);
+            yysize_overflow |= yysize1 < yysize;
+            yysize = yysize1;
+            yyfmt = yystpcpy (yyfmt, yyprefix);
+            yyprefix = yyor;
+          }
+
+      yyf = YY_(yyformat);
+      yysize1 = yysize + yystrlen (yyf);
+      yysize_overflow |= yysize1 < yysize;
+      yysize = yysize1;
+
+      if (yysize_overflow)
+       return YYSIZE_MAXIMUM;
+
+      if (yyresult)
+       {
+          /* Avoid sprintf, as that infringes on the user's name space.
+             Don't have undefined behavior even if the translation
+             produced a string with the wrong number of "%s"s.  */
+          char *yyp = yyresult;
+          int yyi = 0;
+          while ((*yyp = *yyf))
+            {
+              if (*yyp == '%' && yyf[1] == 's' && yyi < yycount)
+                {
+                  yyp += yytnamerr (yyp, yyarg[yyi++]);
+                  yyf += 2;
+                }
+              else
+                {
+                  yyp++;
+                  yyf++;
+                }
+            }
+        }
+      return yysize;
+    }
+}
+#endif /* YYERROR_VERBOSE */
 
 
 #if YYDEBUG
@@ -857,6 +965,12 @@ b4_c_function_def([yyparse], [int], b4_p
   int yyerrstatus;
   /* Look-ahead token as an internal (translated) token number.  */
   int yytoken = 0;
+#if YYERROR_VERBOSE
+  /* Buffer for error messages, and its allocated size.  */
+  char yymsgbuf[128];
+  char *yymsg = yymsgbuf;
+  YYSIZE_T yymsg_alloc = sizeof yymsgbuf;
+#endif
 
   /* Three stacks and their tools:
      `yyss': related to states,
@@ -1158,110 +1272,41 @@ yyerrlab:
   if (!yyerrstatus)
     {
       ++yynerrs;
-#if YYERROR_VERBOSE
-      yyn = yypact[yystate];
-
-      if (YYPACT_NINF < yyn && yyn < YYLAST)
-       {
-         int yytype = YYTRANSLATE (yychar);
-         YYSIZE_T yysize0 = yytnamerr (0, yytname[yytype]);
-         YYSIZE_T yysize = yysize0;
-         YYSIZE_T yysize1;
-         int yysize_overflow = 0;
-         char *yymsg = 0;
-#        define YYERROR_VERBOSE_ARGS_MAXIMUM 5
-         char const *yyarg[YYERROR_VERBOSE_ARGS_MAXIMUM];
-         int yyx;
-
-#if 0
-         /* This is so xgettext sees the translatable formats that are
-            constructed on the fly.  */
-         YY_("syntax error, unexpected %s");
-         YY_("syntax error, unexpected %s, expecting %s");
-         YY_("syntax error, unexpected %s, expecting %s or %s");
-         YY_("syntax error, unexpected %s, expecting %s or %s or %s");
-         YY_("syntax error, unexpected %s, expecting %s or %s or %s or %s");
-#endif
-         char *yyfmt;
-         char const *yyf;
-         static char const yyunexpected[] = "syntax error, unexpected %s";
-         static char const yyexpecting[] = ", expecting %s";
-         static char const yyor[] = " or %s";
-         char yyformat[sizeof yyunexpected
-                       + sizeof yyexpecting - 1
-                       + ((YYERROR_VERBOSE_ARGS_MAXIMUM - 2)
-                          * (sizeof yyor - 1))];
-         char const *yyprefix = yyexpecting;
-
-         /* Start YYX at -YYN if negative to avoid negative indexes in
-            YYCHECK.  */
-         int yyxbegin = yyn < 0 ? -yyn : 0;
-
-         /* Stay within bounds of both yycheck and yytname.  */
-         int yychecklim = YYLAST - yyn;
-         int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
-         int yycount = 1;
-
-         yyarg[0] = yytname[yytype];
-         yyfmt = yystpcpy (yyformat, yyunexpected);
-
-         for (yyx = yyxbegin; yyx < yyxend; ++yyx)
-           if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR)
+#if ! YYERROR_VERBOSE
+      yyerror (]b4_yyerror_args[YY_("syntax error"));
+#else
+      {
+       YYSIZE_T yysize = yysyntax_error (0, yystate, yychar);
+       if (yymsg_alloc < yysize && yymsg_alloc < YYSTACK_ALLOC_MAXIMUM)
+         {
+           YYSIZE_T yyalloc = 2 * yysize;
+           if (! (yysize <= yyalloc && yyalloc <= YYSTACK_ALLOC_MAXIMUM))
+             yyalloc = YYSTACK_ALLOC_MAXIMUM;
+           if (yymsg != yymsgbuf)
+             YYSTACK_FREE (yymsg);
+           yymsg = (char *) YYSTACK_ALLOC (yyalloc);
+           if (yymsg)
+             yymsg_alloc = yyalloc;
+           else
              {
-               if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
-                 {
-                   yycount = 1;
-                   yysize = yysize0;
-                   yyformat[sizeof yyunexpected - 1] = '\0';
-                   break;
-                 }
-               yyarg[yycount++] = yytname[yyx];
-               yysize1 = yysize + yytnamerr (0, yytname[yyx]);
-               yysize_overflow |= yysize1 < yysize;
-               yysize = yysize1;
-               yyfmt = yystpcpy (yyfmt, yyprefix);
-               yyprefix = yyor;
+               yymsg = yymsgbuf;
+               yymsg_alloc = sizeof yymsgbuf;
              }
+         }
 
-         yyf = YY_(yyformat);
-         yysize1 = yysize + yystrlen (yyf);
-         yysize_overflow |= yysize1 < yysize;
-         yysize = yysize1;
-
-         if (!yysize_overflow && yysize <= YYSTACK_ALLOC_MAXIMUM)
-           yymsg = (char *) YYSTACK_ALLOC (yysize);
-         if (yymsg)
-           {
-             /* Avoid sprintf, as that infringes on the user's name space.
-                Don't have undefined behavior even if the translation
-                produced a string with the wrong number of "%s"s.  */
-             char *yyp = yymsg;
-             int yyi = 0;
-             while ((*yyp = *yyf))
-               {
-                 if (*yyp == '%' && yyf[1] == 's' && yyi < yycount)
-                   {
-                     yyp += yytnamerr (yyp, yyarg[yyi++]);
-                     yyf += 2;
-                   }
-                 else
-                   {
-                     yyp++;
-                     yyf++;
-                   }
-               }
-             yyerror (]b4_yyerror_args[yymsg);
-             YYSTACK_FREE (yymsg);
-           }
-         else
-           {
-             yyerror (]b4_yyerror_args[YY_("syntax error"));
+       if (0 < yysize && yysize <= yymsg_alloc)
+         {
+           (void) yysyntax_error (yymsg, yystate, yychar);
+           yyerror (]b4_yyerror_args[yymsg);
+         }
+       else
+         {
+           yyerror (]b4_yyerror_args[YY_("syntax error"));
+           if (yysize != 0)
              goto yyexhaustedlab;
-           }
-       }
-      else
-#endif /* YYERROR_VERBOSE */
-       yyerror (]b4_yyerror_args[YY_("syntax error"));
+         }
+      }
+#endif
     }
 
 ]b4_location_if([[  yyerror_range[0] = yylloc;]])[
@@ -1394,6 +1439,10 @@ yyreturn:
 #ifndef yyoverflow
   if (yyss != yyssa)
     YYSTACK_FREE (yyss);
+#endif
+#if YYERROR_VERBOSE
+  if (yymsg != yymsgbuf)
+    YYSTACK_FREE (yymsg);
 #endif
   return yyresult;
 ]}