avoid null-reference if some nonterminal is not defined

diff --git a/util/LLgen/src/reach.c b/util/LLgen/src/reach.c
index 3fa5110..5bc3e7c 100644 (file)
--- a/util/LLgen/src/reach.c
+++ b/util/LLgen/src/reach.c
@@ -35,7 +35,6 @@ STATIC reachwalk();
 co_reach() {
        /*
         * Check for undefined or unreachable nonterminals.
-        * An undefined nonterminal is a fatal error!
         */
        register p_nont         p;
        register p_start        st;
@@ -50,6 +49,7 @@ co_reach() {
                                p->n_name);
                }
        }
+
        /*
         * Walk the grammar rules, starting with the startsymbols
         * Mark the nonterminals that are encountered with the flag
@@ -106,7 +106,7 @@ reachwalk(p) register p_gram p; {
                        register p_nont n = &nonterms[g_getcont(p)];
 
                        reachable(n);
-                       if (g_gettype(n->n_rule) == EORULE &&
+                       if (p->n_rule && g_gettype(n->n_rule) == EORULE &&
                            ! g_getnpar(p) && (getntparams(n) == 0)) {
                                register p_gram np = p;
                                do {