reports: don't escape the labels

Currently we use "quotearg" to escape the strings output in Dot.  As a
result, if the user's locale is C for instance, all the non-ASCII are
escaped.  Unfortunately graphviz does not interpret this style of
escaping.

For instance:

    5 -> 2 [style=solid label="\"\303\221\303\271\341\271\203\303\251\342\204\235\303\264\""]

was displayed as a sequence of numbers.  We now output:

    5 -> 2 [style=solid label="\"Ñùṃéℝô\""]

independently of the user's locale.

* src/system.h (obstack_backslash): New.
* src/graphviz.h, src/graphviz.c (escape): Remove, use
obstack_backslash instead.
* src/print-graph.c: Likewise.
* tests/report.at: Adjust.

src/graphviz.c

@@ -72,18 +72,20 @@ output_edge (int source, int destination, char const *label,
 {
   fprintf (fout, "  %d -> %d [style=%s", source, destination, style);
   if (label)
-    fprintf (fout, " label=%s", quote (label));
+    {
+      fputs (" label=\"", fout);
+      for (const char *cp = label; *cp; ++cp)
+        switch (*cp)
+        {
+        case '"':  fputs ("\\\"", fout); break;
+        case '\\': fputs ("\\\\", fout); break;
+        default:   fputc (*cp,    fout); break;
+        }
+      fputc ('"', fout);
+    }
   fputs ("]\n", fout);
 }
 
-char const *
-escape (char const *name)
-{
-  char *q = quote (name);
-  q[strlen (q) - 1] = '\0';
-  return q + 1;
-}
-
 static void
 no_reduce_bitset_init (state const *s, bitset *no_reduce_set)
 {
@@ -149,7 +151,7 @@ print_token (struct obstack *out, bool first, char const *tok)
 {
   if (! first)
     obstack_sgrow (out, ", ");
-  obstack_sgrow (out, escape (tok));
+  obstack_backslash (out, tok);
   return false;
 }
 

src/graphviz.h

@@ -63,10 +63,4 @@ void output_red (state const *s, reductions const *reds, FILE *fout);
  */
 void finish_graph (FILE *fout);
 
-/** Escape a lookahead token.
- *
- * \param name         the token.
- */
-char const *escape (char const *name);
-
 #endif /* ! GRAPHVIZ_H_ */

src/print-graph.c

@@ -72,19 +72,28 @@ print_core (struct obstack *oout, state *s)
         obstack_printf (oout, "%*s| ",
                         (int) strlen (previous_lhs->symbol->tag), "");
       else
-        obstack_printf (oout, "%s: ", escape (r->lhs->symbol->tag));
+        {
+          obstack_backslash (oout, r->lhs->symbol->tag);
+          obstack_printf (oout, ": ");
+        }
       previous_lhs = r->lhs;
 
       for (item_number const *sp = r->rhs; sp < sp1; sp++)
-        obstack_printf (oout, "%s ", escape (symbols[*sp]->tag));
+        {
+          obstack_backslash (oout, symbols[*sp]->tag);
+          obstack_1grow (oout, ' ');
+        }
 
       obstack_1grow (oout, '.');
 
       if (0 <= *r->rhs)
         for (item_number const *sp = sp1; 0 <= *sp; ++sp)
-          obstack_printf (oout, " %s", escape (symbols[*sp]->tag));
+          {
+            obstack_1grow (oout, ' ');
+            obstack_backslash (oout, symbols[*sp]->tag);
+          }
       else
-        obstack_printf (oout, " %%empty");
+        obstack_sgrow (oout, " %empty");
 
       /* Experimental feature: display the lookahead tokens. */
       if (report_flag & report_lookahead_tokens
@@ -104,7 +113,7 @@ print_core (struct obstack *oout, state *s)
               BITSET_FOR_EACH (biter, reds->lookahead_tokens[redno], k, 0)
                 {
                   obstack_sgrow (oout, sep);
-                  obstack_sgrow (oout, escape (symbols[k]->tag));
+                  obstack_backslash (oout, symbols[k]->tag);
                   sep = ", ";
                 }
               obstack_1grow (oout, ']');

src/system.h

@@ -171,6 +171,23 @@ typedef size_t uintptr_t;
 # define obstack_sgrow(Obs, Str) \
   obstack_grow (Obs, Str, strlen (Str))
 
+/* Output Str escaped to be a string.
+
+   For instance "\"foo\"" -> "\\\"foo\\\"".  */
+
+# define obstack_backslash(Obs, Str)                    \
+  do {                                                  \
+    char const *p__;                                    \
+    for (p__ = Str; *p__; p__++)                        \
+      switch (*p__)                                     \
+        {                                               \
+        case '"':  obstack_sgrow (Obs, "\\\""); break;  \
+        case '\\': obstack_sgrow (Obs, "\\\\"); break;  \
+        default:   obstack_1grow (Obs, *p__);   break;  \
+        }                                               \
+  } while (0)
+
+
 /* Output Str escaped for our postprocessing (i.e., escape M4 special
    characters).