segfault in Array.append in rare case

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@13113 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

byterun/array.c

@@ -319,12 +319,13 @@ static value caml_array_gather(intnat num_arrays,
            count--, src++, pos++) {
         caml_initialize(&Field(res, pos), *src);
       }
+    }
+    Assert(pos == size);
+
     /* Many caml_initialize in a row can create a lot of old-to-young
        refs.  Give the minor GC a chance to run if it needs to. */
     res = caml_check_urgent_gc(res);
   }
-    Assert(pos == size);
-  }
   CAMLreturn (res);
 }