The boost::function FAQ item 3 specifically addresses the scenario I am interested in:
Why are there workarounds for void returns? C++ allows them! Void returns are permitted by the C++ standard, as in this code snippet:
void f(); void g() { return f(); }This is a valid usage of boost::function because void returns are not used. With void returns, we would attempting to compile ill-formed code similar to:
int f(); void g() { return f(); }In essence, not using void returns allows boost::function to swallow a return value. This is consistent with allowing the user to assign and invoke functions and function objects with parameters that don't exactly match.
Unfortunately, this doesn't work in VS2008:
int Foo();
std::tr1::function<void()> Bar = Foo;
This produces errors starting with:
c:\Program Files\Microsoft Visual Studio 9.0\VC\include\xxcallfun(7) : error C2562: 'std::tr1::_Callable_fun<_Ty>::_ApplyX' : 'void' function returning a value
Is this a failing of the VS2008 TR1 implementation? Does this work in VS2010? Does TR1 address this capability? How about C++0x?