pic->irep is a root marker

src/codegen.c

@@ -316,6 +316,9 @@ codegen(codegen_state *state, pic_value obj, bool tailpos)
 	irep->code[irep->clen].u.i = k;
 	irep->clen++;
 
+        /* prevent GC from hanging */
+        pic->irep[k] = NULL;
+
 	pic->irep[k] = codegen_lambda(state, obj);
 	break;
       }

src/gc.c

@@ -492,6 +492,12 @@ gc_mark_phase(pic_state *pic)
     gc_mark(pic, pic->globals[i]);
   }
 
+  /* irep */
+  for (i = 0; i < pic->ilen; ++i) {
+    if (pic->irep[i])
+      gc_mark_object(pic, (struct pic_object *)pic->irep[i]);
+  }
+
   /* pool */
   for (i = 0; i < pic->plen; ++i) {
     gc_mark(pic, pic->pool[i]);