boost bind callback function pointer as a parameter

Question

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?

Collin Dauphinee · Accepted Answer · 2011-11-22 01:35:22Z

3

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.

answered Nov 22, 2011 at 1:35

Collin Dauphinee

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1 Comment

Anthony Over a year ago

+1, I forgot to mention alternatives to using a member function.

Anthony · Accepted Answer · 2011-11-22 01:48:14Z

2

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.

edited Nov 22, 2011 at 1:48

answered Nov 22, 2011 at 1:33

Anthony

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1 Comment

Collin Dauphinee Over a year ago

Close enough, but the placeholders are in an unnamed namespace.

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