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    <p>The code you wrote is perfectly valid. There's nothing wrong with it (aside from the fact that <code>Derived::a</code> is private). It is well-formed and the behavior is defined (so far). As the quoted portion of the standard says, it is perfectly legal to upcast member pointers using an explicit <code>static_cast</code>, which is exactly what you are doing. 5.2.9/9 never says that the pointed member has to be present in the base class.</p> <p>Also, as you correctly quoted from the standard, the presence of the actual member in the object is required <em>later</em> at the moment of <em>dereference</em> of the pointer, not at the moment of initialization. This, of course, depends on the dynamic type of the object used at the left-hand side of member-access operator (<code>-&gt;*</code> or <code>.*</code>). The type is only known at run-time and thus cannot be checked by the compiler. </p> <p>This requirement is included as a mere note into 5.2.9/9, but it is reiterated in a more formal form in 5.5/4</p> <blockquote> <p>4 If the dynamic type of the object does not contain the member to which the pointer refers, the behavior is undefined.</p> </blockquote> <p>So, for example, in the context of your example the following lines of code are well-formed</p> <pre><code>Base b; b.*pa; // 1 Derived d; d.*pa; // 2 Base *pb = &amp;d; pb-&gt;*pa; // 3 </code></pre> <p>However, the first dereference produces undefined behavior (since object <code>b</code> does not contain the member), while both the second one and the third one are perfectly legal.</p>
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    1. COExcellent answer. But I can't resist mentioning that `sizeof b.*pa` gives defined behaviour, despite "dereferencing" a nonexistent member. (Because nothing in C++ is simple... :-P)
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    2. CO@j_random_hacker: Well, yes. In my case the occurence of undefined behavior is tied to the process of pointer dereference during the *evaluation* of the expression, while in case of `sizeof` the argument is never evaluated.
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    3. COVC emits C4407 warning when I static_cast a pointer to function member of derived class to the second base type, so according to the standard and your answer, it's not standard conformant, right ?
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