X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/720e5c1bc36411c1a0591a525a897f47cfd17987..80a697503460fcf0d52bed9fb3b86e4c276fb37e:/src/derives.c

diff --git a/src/derives.c b/src/derives.c
index f0c41165..ab7cc326 100644
--- 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)
@@ -51,7 +45,7 @@ print_derives (void)
 	  fprintf (stderr, "\t\t%d:", *sp);
 	  for (rhsp = ritem + rule_table[*sp].rhs; *rhsp > 0; ++rhsp)
 	    fprintf (stderr, " %s", tags[*rhsp]);
-	  fputc ('\n', stderr);
+	  fprintf (stderr, " (rule %d)\n", -*rhsp);
 	}
     }
 
@@ -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);