CODEWITHSUNDEEP
c++boostcallbackboost-bind
Ivan Santos
Ivan Santos

Reputation: 634

boost bind callback function pointer as a parameter

I am trying to pass a function pointer using boost::bind. 

void
Class::ThreadFunction(Type(*callbackFunc)(message_type::ptr&))
{
}

boost::shared_ptr<boost::thread>
Class::Init(Type(*callbackFunc)(message_type::ptr&))
{
    return boost::shared_ptr<boost::thread> (
        new boost::thread(boost::bind(&Class::ThreadFunction, callbackFunc))
        );
}

I get the following errors:

1>C:\dev\sapphire\boost_1_46_1\boost/bind/mem_fn.hpp(362) : warning C4180: qualifier applied to function type has no meaning; ignored
1>C:\dev\sapphire\boost_1_46_1\boost/bind/mem_fn.hpp(333) : error C2296: '->*' : illegal, left operand has type 'Type (__cdecl **)(message_type::ptr &)'

However, I was able to change to the following, it works fine:

void
ThreadFunction(Type(*callbackFunc)(message_type::ptr&))
{
}

boost::shared_ptr<boost::thread>
Class::Init(Type(*callbackFunc)(message_type::ptr&))
{
    return boost::shared_ptr<boost::thread> (
        new boost::thread(boost::bind(&ThreadFunction, callbackFunc))
        );
}

Why do I get those errors if I declare the method in the Class class?

Upvotes: 1

Views: 3049

Answers (2)

Anthony
Anthony

Reputation: 12387

Because you need to bind an instance of Class as well. Read the Boost documentation.

I think you need this:

boost::thread(boost::bind(
    &Class::ThreadFunction, &someClassInstance, _1), 
    callbackFunc);

Note: above code snippet is off the top of my head. I think it's correct though.

Upvotes: 2

Collin Dauphinee
Collin Dauphinee

Reputation: 13973

When you bind a non-static member function, you need to provide the this pointer that will be used. If you don't want the function associated with a particular instance of Class, you should make the function static. 

struct Class {
    void foo(int) { }
    static void bar(int) { }
};

std::bind(&Class::foo, 5); // Illegal, what instance of Class is foo being called
                           // on?

Class myClass;
std::bind(&Class::foo, &myClass, 5); // Legal, foo is being called on myClass.

std::bind(&Class::bar, 5); // Legal, bar is static, so no this pointer is needed.

Upvotes: 3

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