Extract the return type of a function without calling it (using templates?)

Question

I\'m looking for a way in C++ to extract the return type of a function (without calling it). I presume this will require some template magic.

float Foo();
i         


        

Answer 1

Here comes the template magic (no Boost is involved):

template  class clFunc0
{
    typedef ReturnType ( *FuncPtr )();
public:
    typedef ReturnType Type;
};

template  inline clFunc0 ResultType( ReturnType ( *FuncPtr )() )
{
    return clFunc0();
}

#define FUNC_TYPE( func_name ) decltype( ResultType( &func_name ) )::Type

int test()
{
    return 1;
}

int main()
{
    FUNC_TYPE( test ) Value = 1;

    return Value;
}

And compile it via

gcc Test.cpp -std=gnu++0x