X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/c87d4863f6de617e0ed35dc566c59d5b4a072101..b9752825a023753145900b00a3f16394e183be60:/src/derives.c

diff --git a/src/derives.c b/src/derives.c
index 3a34a30f..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"
@@ -31,22 +26,27 @@
 #include "gram.h"
 #include "derives.h"
 
-short **derives;
-
+short **derives = NULL;
 
 static void
 print_derives (void)
 {
   int i;
-  short *sp;
 
   fputs ("DERIVES\n", stderr);
 
   for (i = ntokens; i < nsyms; i++)
     {
+      short *sp;
       fprintf (stderr, "\t%s derives\n", tags[i]);
       for (sp = derives[i]; *sp > 0; sp++)
-	fprintf (stderr, "\t\t%d (%s)\n", *sp, tags[*sp]);
+	{
+	  short *rhsp;
+	  fprintf (stderr, "\t\t%d:", *sp);
+	  for (rhsp = ritem + rule_table[*sp].rhs; *rhsp > 0; ++rhsp)
+	    fprintf (stderr, " %s", tags[*rhsp]);
+	  fprintf (stderr, " (rule %d)\n", -*rhsp);
+	}
     }
 
   fputs ("\n\n", stderr);
@@ -57,7 +57,6 @@ void
 set_derives (void)
 {
   int i;
-  int lhs;
   shorts *p;
   short *q;
   shorts **dset;
@@ -68,16 +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);