Leaked Mock Objects when using GoogleMock together with Boost::Shared Pointers

Question

For this special scenario, I am not able to get rid of the leaks.

I get the message of Leaked Mock Objects when executing the test. The concrete Message:

ClassElementFixture.h:102: ERROR: this mock object (used in test ClassElementFixture.initialize) should be deleted but never is. Its address is @0x940a650.

I marked the line to which the error refers. Here a simplified version of my code:

...
class ClassElementFixture: public ::testing::Test
{
    public:
        boost::shared_ptr<fesa::ClassElement> classElement_;
        boost::shared_ptr<fesa::DeviceElementMock> deviceElement_;

        ...

        void SetUp()
        {
            classElement_.reset(new fesa::ClassElement());
        }

        void TearDown()
        {
        }

        void initializeFake()
        {
            fesa::ParserElementFactoryMock factory;
            deviceElement_.reset(new fesa::DeviceElementMock());

            EXPECT_CALL(factory, createDeviceElement(_))
                        .WillOnce(Return(deviceElement1_));
            EXPECT_CALL(*deviceElement_, initialize(_));//Error refers to here

            classElement_->initialize(factory);

            EXPECT_TRUE(Mock::VerifyAndClearExpectations(deviceElement_.get()));
        }
}

I already found Why is GoogleMock leaking my shared_ptr?

at Stack-Overflow, which is related. However the suggestions from there do not fix my problem :X

The only possibility which I found, in order to at least suppress the error is:

Mock::AllowLeak(deviceElement_.get());

However this is not a very clean solution =)

So how to get rid of the leaks properly?

Do you have a cycle in your shared_ptr relationships? There's a known issue with shared pointers where cycles can lead to leaks. — Chris Hayden, Jun 01 '13 at 16:52
I just saw your comments ... sorry for my long response-time(I have to enable email-notification). Since I posted the problem, the implementation of the used classes has changed. So I am not able to reproduce the bug any more :X I just removed all the Mock::AlowLeak, and things work fine now. I think it realy could be caused by a circular dependency ... thinks like that were used in the old code .. so anyhow, thanks for your help! — Alex, Jul 10 '13 at 12:07

Chris Drew · Accepted Answer · 2017-04-07T09:09:34.770

If you use smart pointers, you still need to have a clear idea of ownership otherwise you can get poor performance, cyclic dependencies and memory leaks.

I suggest the default choice of smart pointer should be unique_ptr for unique ownership and use raw pointers for observers.

If the observers could potentially outlive the owner then move to one shared_ptr for the owner and weak_ptr for the observers.

Only use "shared" shared_ptr as a last resort when you don't have one clear owner and be careful of cyclic dependencies.

score 2 · Answer 2 · answered Nov 27 '13 at 21:51

2

Don't use shared pointers. Or if you really have to use them make sure they reach back to 0 and get destroyed at the end of the test.

answered Nov 27 '13 at 21:51

Sorin

11,863
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score 2 · Answer 3 · answered Mar 08 '16 at 23:15

It's an old question, but I don't see anyone mentioning the solution I just found.

I saw the same error until I added a virtual destructor to the class I was mocking. In your case, make sure you've got a virtual destructor on ParserElementFactoryMock. Makes sense, as without the virtual destructor the mock object will not free their resources when going out of scope.

Leaked Mock Objects when using GoogleMock together with Boost::Shared Pointers

3 Answers3