The R Project SVN – R – Diff – /trunk/src/main/array.c

 	    for (i = 0; i < nans; i++)
 		SET_STRING_ELT(ans, i, STRING_ELT(vals, i % lendat));
 	break;
     case VECSXP:
     case EXPRSXP:
+#ifdef SWITCH_TO_REFCNT
 	if (nans && lendat)
 	    for (i = 0; i < nans; i++)
 		SET_VECTOR_ELT(ans, i, VECTOR_ELT(vals, i % lendat));
+#else
+	if (nans && lendat) {
+	    /* Need to guard against possible sharing of values under
+	       NAMED.  This is not needed with reference
+	       coutning. (PR#15919) */
+	    Rboolean needsmark = (lendat < nans || MAYBE_REFERENCED(vals));
+	    for (i = 0; i < nans; i++) {
+		SEXP elt = VECTOR_ELT(vals, i % lendat);
+		if (needsmark || MAYBE_REFERENCED(elt))
+		    MARK_NOT_MUTABLE(elt);
+		SET_VECTOR_ELT(ans, i, elt);
+	    }
+	}
+#endif
 	break;
     default:
 	// excluded above
 	break;
+    }

The R Project SVN R