compile.c: fix load_from_binary

* compile.c (ibf_load_iseq_each): realpath may be nil.  follow up
  r59709.  [fix https://github.com/Shopify/bootsnap/issues/132]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62617 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -8708,7 +8708,8 @@ ibf_load_iseq_each(const struct ibf_load *load, rb_iseq_t *iseq, ibf_offset_t of
 		rb_raise(rb_eRuntimeError, "path object size mismatch");
 	    }
 	    path = rb_fstring(RARRAY_AREF(pathobj, 0));
-	    realpath = rb_fstring(RARRAY_AREF(pathobj, 1));
+	    realpath = RARRAY_AREF(pathobj, 1);
+	    if (!NIL_P(realpath)) realpath = rb_fstring(realpath);
 	}
 	else {
 	    rb_raise(rb_eRuntimeError, "unexpected path object");

test/ruby/test_iseq.rb

@@ -398,10 +398,9 @@ class TestISeq < Test::Unit::TestCase
 
   def test_to_binary_with_objects
     code = "[]"+100.times.map{|i|"<</#{i}/"}.join
-    bin = assert_nothing_raised {
-      RubyVM::InstructionSequence.compile(code).to_binary
-    }
-    # load_from_binary doesn't work now
-    assert_instance_of(String, bin)
+    iseq = RubyVM::InstructionSequence.compile(code)
+    bin = assert_nothing_raised {iseq.to_binary}
+    iseq2 = RubyVM::InstructionSequence.load_from_binary(bin)
+    assert_equal(iseq2.to_a, iseq.to_a)
   end
 end