* src/gram.c (ritem_print): Be sure to subtract 1 when displaying

[bison.git] / src / derives.c

diff --git a/src/derives.c b/src/derives.c
index f0c41165a8bca1eadae1775612cf7892238dce8a..80e430bf71f24a44b9499591dac1cc09ae1cc4fc 100644 (file)
--- a/src/derives.c
+++ b/src/derives.c
@@ -19,11 +19,6 @@
    Boston, MA 02111-1307, USA.  */
 
 
-/* set_derives finds, for each variable (nonterminal), which rules can
-   derive it.  It sets up the value of derives so that derives[i -
-   ntokens] points to a vector of rule numbers, terminated with -1.
-   */
-
 #include "system.h"
 #include "getargs.h"
 #include "types.h"
@@ -31,8 +26,7 @@
 #include "gram.h"
 #include "derives.h"
 
-short **derives;
-
+short **derives = NULL;
 
 static void
 print_derives (void)
@@ -49,9 +43,9 @@ print_derives (void)
        {
          short *rhsp;
          fprintf (stderr, "\t\t%d:", *sp);
-         for (rhsp = ritem + rule_table[*sp].rhs; *rhsp > 0; ++rhsp)
+         for (rhsp = &ritem[rule_table[*sp].rhs]; *rhsp >= 0; ++rhsp)
            fprintf (stderr, " %s", tags[*rhsp]);
-         fputc ('\n', stderr);
+         fprintf (stderr, " (rule %d)\n", -*rhsp - 1);
        }
     }
 
@@ -63,7 +57,6 @@ void
 set_derives (void)
 {
   int i;
-  int lhs;
   shorts *p;
   short *q;
   shorts **dset;
@@ -74,16 +67,14 @@ set_derives (void)
 
   p = delts;
   for (i = nrules; i > 0; i--)
-    {
-      lhs = rule_table[i].lhs;
-      if (lhs >= 0)
-       {
-         p->next = dset[lhs];
-         p->value = i;
-         dset[lhs] = p;
-         p++;
-       }
-    }
+    if (rule_table[i].useful)
+      {
+       int lhs = rule_table[i].lhs;
+       p->next = dset[lhs];
+       p->value = i;
+       dset[lhs] = p;
+       p++;
+      }
 
   derives = XCALLOC (short *, nvars) - ntokens;
   q = XCALLOC (short, nvars + nrules);