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POCast between function pointers
 

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    <p>I am currently implementing a timer/callback system using Don Clugston's fastdelegates. (see <a href="http://www.codeproject.com/KB/cpp/FastDelegate.aspx" rel="nofollow noreferrer">http://www.codeproject.com/KB/cpp/FastDelegate.aspx</a>)</p> <p>Here is the starting code:</p> <pre><code>struct TimerContext { }; void free_func( TimerContext* ) { } struct Foo { void member_func( TimerContext* ) { } }; Foo f; MulticastDelegate&lt; void (TimerContext*) &gt; delegate; delegate += free_func; delegate += bind( &amp;Foo::member_func, &amp;f ); </code></pre> <p>Okay, but now, i wish the user to be able to subclass <code>TimerContext</code> to store and send his own structures to the callbacks. The purpose here is to prevent the user from having to downcast the <code>TimerContext</code> himself</p> <pre><code>struct TimerContext { }; struct MyTimerContext : TimerContext { int user_value; }; void free_func( TimerContext* ) { } void free_func2( MyTimerContext* ) { } struct Foo { void member_func( TimerContext* ) { } void member_func2( MyTimerContext* ) { } }; Foo f; MulticastDelegate&lt; void (TimerContext*) &gt; delegate; delegate += free_func; delegate += free_func2; delegate += bind( &amp;Foo::member_func, &amp;f ); delegate += bind( &amp;Foo::member_func2, &amp;f ); </code></pre> <p>As you guessed, GCC won't let me do that :)</p> <pre><code>error: invalid conversion from `void (*)(MyTimerContext*)' to `void (*)(TimerContext*)' error: initializing argument 1 of `delegate::Delegate&lt;R ()(Param1)&gt;::Delegate(R (*)(Param1)) [with R = void, Param1 = TimerContext*]' </code></pre> <p>So now my question is: If I force the cast using <code>reinterpret_cast</code>, it'll work, but will it be safe ?</p> <p>PS: These are time-critical callbacks, heavy virtual-oriented solutions are considered impracticable :/</p>
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