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    <p>I found the answer to my own question.</p> <p><code>returns_reference</code> returns a type with size > 1 if the return type of the function is a reference.</p> <p>It works in most scenarios, but the number of combinations of <code>const</code> and <code>volatile</code> increases exponentially with the number of parameters. </p> <p>Whenever it doesn't work -- whether because we have more than one argument or whether overload resolution is rather obscure (for example, when the <code>const</code> version of <code>operator()</code> works, but the non-<code>const</code> version doesn't), the user should use <code>reftype</code> on all arguments before passing them to <code>returns_reference</code>.</p> <p>I <em>think</em> the <code>reftype</code> version might still have a <em>few</em> edge-cases in C++11 (regarding r-value references that are in fact l-lvalues), but it's "good enough" for me for now. At that point, the question of what's actually a "reference" is itself ambiguous anyway. (Although, if we're using C++11, we can just use <code>decltype</code> and forget about all this. The only situation we would still use this under C++11 is if the compiler doesn't support <code>decltype</code> but does support r-value references.)</p> <pre><code>template&lt;bool B&gt; struct static_bool { unsigned char _[B + 1]; static_bool(...) { } operator bool() const { return B; } }; static_bool&lt;false&gt; returns_reference(...) { return false; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T &amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T &amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T const &amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T const &amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T volatile &amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T volatile &amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T const volatile &amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T const volatile &amp;) { return NULL; } template&lt;class T&gt; struct type_wrapper { }; template&lt;class T&gt; type_wrapper&lt;T &amp;&gt; reftype(T &amp;) { return type_wrapper&lt;T &amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T const &amp;&gt; reftype(T const &amp;) { return type_wrapper&lt;T const &amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T volatile &amp;&gt; reftype(T volatile &amp;) { return type_wrapper&lt;T volatile &amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T const volatile &amp;&gt; reftype(T const volatile &amp;) { return type_wrapper&lt;T const volatile &amp;&gt;(); } #if __cplusplus &gt;= 201103L template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T &amp;&amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T &amp;&amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T const &amp;&amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T const &amp;&amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T volatile &amp;&amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T volatile &amp;&amp;) { return NULL; } template&lt;class T, class F&gt; static_bool&lt;!!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T const volatile &amp;&amp;(*)(void)&gt;(0) ()))&gt; returns_reference(F, T const volatile &amp;&amp;) { return NULL; } template&lt;class T&gt; type_wrapper&lt;T &amp;&amp;&gt; reftype(T &amp;&amp;) { return type_wrapper&lt;T &amp;&amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T const &amp;&amp;&gt; reftype(T const &amp;&amp;) { return type_wrapper&lt;T const &amp;&amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T volatile &amp;&amp;&gt; reftype(T volatile &amp;&amp;) { return type_wrapper&lt;T volatile &amp;&amp;&gt;(); } template&lt;class T&gt; type_wrapper&lt;T const volatile &amp;&amp;&gt; reftype(T const volatile &amp;&amp;) { return type_wrapper&lt;T const volatile &amp;&amp;&gt;(); } #endif template&lt;class T, class F&gt; static_bool&lt; !!sizeof(&amp;(static_cast&lt;F(*)()&gt;(0) ())(static_cast&lt;T (*)(void)&gt;(0) ())) &gt; returns_reference(type_wrapper&lt;F&gt;, type_wrapper&lt;T&gt; = type_wrapper&lt;T&gt;()) { return NULL; } </code></pre> <p>Test code:</p> <pre><code>struct Test { Test() { } Test(Test &amp;) { } Test(Test const &amp;) { } Test(Test volatile &amp;) { } Test(Test const volatile &amp;) { } Test *operator()(Test *p) const; Test const *operator()(Test const *p) const; Test volatile *operator()(Test volatile *p) const; Test const volatile *operator()(Test const volatile *p) const; Test &amp;operator()(Test &amp;p) const; Test const &amp;operator()(Test const &amp;p) const; Test volatile &amp;operator()(Test volatile &amp;p) const; Test const volatile &amp;operator()(Test const volatile &amp;p) const; #if __cplusplus &gt;= 201103L || defined(_MSC_VER) &amp;&amp; _MSC_VER &gt;= 1700 Test &amp;&amp;operator()(Test &amp;&amp;p) const { return std::move(p); } Test const &amp;&amp;operator()(Test const &amp;&amp;p) const; Test volatile &amp;&amp;operator()(Test volatile &amp;&amp;p) const; Test const volatile &amp;&amp;operator()(Test const volatile &amp;&amp;p) const; #endif }; Test *test1(Test *p); Test const *test2(Test const *p); Test volatile *test3(Test volatile *p); Test const volatile *test4(Test const volatile *p); Test &amp;test5(Test &amp;p); Test const &amp;test6(Test const &amp;p); Test volatile &amp;test7(Test volatile &amp;p); Test const volatile &amp;test8(Test const volatile &amp;p); #if __cplusplus &gt;= 201103L || defined(_MSC_VER) &amp;&amp; _MSC_VER &gt;= 1700 Test &amp;&amp;test9(Test &amp;&amp;p); Test const &amp;&amp;test10(Test const &amp;&amp;p); Test volatile &amp;&amp;test11(Test volatile &amp;&amp;p); Test const volatile &amp;&amp;test12(Test const volatile &amp;&amp;p); #endif int main() { Test t; (void)t; Test const tc; (void)tc; Test volatile tv; (void)tv; Test const volatile tcv; (void)tcv; std::cerr &lt;&lt; (sizeof(returns_reference( t , &amp;t )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , &amp;tc )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , &amp;tv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , &amp;tcv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , t )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , tc )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , tv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( t , tcv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test1 , &amp;t )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test2 , &amp;tc )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test3 , &amp;tv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test4 , &amp;tcv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test5 , t )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test6 , tc )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test7 , tv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test8 , tcv )) != sizeof(unsigned char)) &lt;&lt; std::endl; #if __cplusplus &gt;= 201103L || defined(_MSC_VER) &amp;&amp; _MSC_VER &gt;= 1700 std::cerr &lt;&lt; (sizeof(returns_reference( test9 , t )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test10 , tc )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test11 , tv )) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference( test12 , tcv )) != sizeof(unsigned char)) &lt;&lt; std::endl; #endif std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(&amp;t ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(&amp;tc ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(&amp;tv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(&amp;tcv))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(t ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(tc ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(tv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(t ), reftype(tcv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test1 ), reftype(&amp;t ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test2 ), reftype(&amp;tc ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test3 ), reftype(&amp;tv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test4 ), reftype(&amp;tcv))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test5 ), reftype(t ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test6 ), reftype(tc ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test7 ), reftype(tv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test8 ), reftype(tcv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; #if __cplusplus &gt;= 201103L || defined(_MSC_VER) &amp;&amp; _MSC_VER &gt;= 1700 std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test9 ), reftype(t ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test10), reftype(tc ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test11), reftype(tv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; std::cerr &lt;&lt; (sizeof(returns_reference(reftype(test12), reftype(tcv ))) != sizeof(unsigned char)) &lt;&lt; std::endl; #endif return 0; } </code></pre>
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    1. POHow to determine if a function returns a reference in C++03?
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    1. COHmm g++4.8.1 compiles it, but VS2010 says `error C2064: term does not evaluate to a function taking 1 arguments` for all of the `returns_reference` overloads.
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    2. CO@DyP: It works in VS 2013... I don't have the time to look at it right now unfortunately though.
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    3. COBesides that, I think you can simplify the static-cast-to-create-a-variable by using `declval` (`template<class T> T declval();`, watch out for lvalue/rvalueness), e.g. `template<class T, class F> static_bool<!!sizeof(&(declval<F>()(declval<T&>())))> returns_reference(F, T &) { return NULL; }` Also, I'm not sure what those cv-overloads are there for; you can bind an `int const` to a `T&`, see [temp.deduct.call]/3 (you'll need one `T const&` overload for rvalue arguments, though)
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