Question

g++ complains about

myclass.cxx:185: error: no matching function for call to 'IMyInterface::doSomething(const SomeClass*, unsigned int)'
IMyInterface.h:34: note: candidates are: virtual void IMyInterface::doSomething(const SomeClass*&, unsigned int)

when I call

m_instanceOfInterface->doSomething((const SomeClass*)0,(unsigned int)1);

Any pointers to why? It seems to me that g++ is seeing exactly the same signature between what is declared and what is being called, but still complains about no matching function found.

I can call, in the same context, another function of IMyInteface, IMyInterface::doSomethingElse(float& p). So somehow the const is the problem?

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I did not pass the NULL pointer and cast a constant integer just for fun… originally I have

m_instanceOfInterface->doSomething((const SomeClass*)m_someDerivedClass,m_anInteger);

and got the same error. So I decided to clarify things with g++ by giving some explicit arguments. I can assure you that the NULL pointer is NOT the problem – although understandably we all cringed a bit when seeing a NULL being passed with const 🙂

Answer 1

The function requires its argument by non-const reference, which cannot bind to a temporary. Observe:

void foo(int, T &);
foo(1, T()); // error, cannot bind to temporary

In your case, T = SomeClass const *. So, you have provide a non-temporary:

SomeClass const * pc = 0;
m_instanceOfInterface->doSomething(pc, 1U);

Note that the purpose of this is presumably to fill pc with some meaningful value, so be sure to incorporate that apporpriately.