how to mock global free function using gmock

I am using VS2005, and gmock 1.6. I am facing a problem to mock free global functions. I looked into google cookbook, their solution requires me to change the original sources and I don't want to do that. I tried to mock it using global mock object, but in that case I get memory leaks or the error that the mock object should be deleted but never is.

So, the problem is as follows:

I have a global function:

A* foo();

I have a mock class

class MockA : public A {
public:
    MOCK_METHOD0 (bar1, bool());  
    MOCK_METHOD0 (bar2, bool());

};

In the sources, the global function is used in the following manner:

if (foo()->bar1()){  
   // do something
}

if (foo()->bar2()){  
   // do something
}

I cannot find a way to mock this behavior. I tried to wrap the global function "foo()" in an interface class and used global mock object to access it but I get memory leaks when TearDown() is called. Maybe I didn't do it properly. I did it like this:

struct IFoo {  
    virtual A* foo() = 0;  
    virtual ~IFoo() {}  
};  

struct FooMock : public IFoo {  
    FooMock() {}  
    virtual ~FooMock() {}  
    MOCK_METHOD0(foo, A*());  
};

FooMock fooMock;    // global mock object

// foo() implementation  
A* foo() {  
    return fooMock.foo();  
}  

In the SetUp() function, I set Expectations on the global object like

EXPECT_CALL(fooMock,foo())  
    .Times(1)  
    .WillOnce(Return(&mockObj));  

where mockObj is declared in the Test class. TEST(..., instA) {

    // ...
}

I cannot change the original sources, so what other options do we have?