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    <p>I don't believe it's the deficiency of const-correctness per se, but rather the lack of convenient ability to generalize a method over cv-qualifiers (in the same way we can generalize over types via templates). Hypothetically, imagine if you could write something like:</p> <pre><code>template&lt;cvqual CV&gt; inline CV ITEMIDLIST* GetNextItem(CV ITEMIDLIST * pidl) { return pidl ? reinterpret_cast&lt;CV ITEMIDLIST *&gt;(reinterpret_cast&lt;CV BYTE *&gt;(pidl) + pidl-&gt;mkid.cb) : NULL; } ITEMIDLIST o; const ITEMIDLIST co; ITEMIDLIST* po = GetNextItem(&amp;o); // CV is deduced to be nothing ITEMIDLIST* pco = GetNextItem(&amp;co); // CV is deduced to be "const" </code></pre> <p>Now you can actually do this kind of thing with template metaprogramming, but this gets messy real quick:</p> <pre><code>template&lt;class T, class TProto&gt; struct make_same_cv_as { typedef T result; }; template&lt;class T, class TProto&gt; struct make_same_cv_as&lt;T, const TProto&gt; { typedef const T result; }; template&lt;class T, class TProto&gt; struct make_same_cv_as&lt;T, volatile TProto&gt; { typedef volatile T result; }; template&lt;class T, class TProto&gt; struct make_same_cv_as&lt;T, const volatile TProto&gt; { typedef const volatile T result; }; template&lt;class CV_ITEMIDLIST&gt; inline CV_ITEMIDLIST* GetNextItem(CV_ITEMIDLIST* pidl) { return pidl ? reinterpret_cast&lt;CV_ITEMIDLIST*&gt;(reinterpret_cast&lt;typename make_same_cv_as&lt;BYTE, CV_ITEMIDLIST&gt;::result*&gt;(pidl) + pidl-&gt;mkid.cb) : NULL; } </code></pre> <p>The problem with the above is the usual problem with all templates - it'll let you pass object of any random type so long as it has the members with proper names, not just <code>ITEMIDLIST</code>. You can use various "static assert" implementations, of course, but that's also a hack in and of itself.</p> <p>Alternatively, you can use the templated version to reuse the code inside your .cpp file, and then wrap it into a const/non-const pair and expose that in the header. That way, you pretty much only duplicate function signature. </p>
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    1. COI badly want to attend a really good intensive template type programming course. The above looks insane - especially for this particular problem. And is the source of my current reluctance to really delve deeply into template type metaprogramming. It just looks like it grows out of control quickly, and I lose the thread of the actual core of what I'm doing too quickly. Language tools are great if I can grok them deeply enough to really leverage them, and offer a lever to my consumers. But if it leaves my jaw hanging, and is opaque to my consumers... I have to question its eal utilty.
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    2. CO[Please don't misunderstand the scope of my criticism of templates: they have huge uses. I am only questioning the ultimate utility of type metaprogramming, at least for me, as I have yet to grok it deeply enough to really make it a tool and not a headache :) ]
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    3. COTMP as applied here is really just a way of saying "if you give me type T with traits X, I give you type U with the same trait X". By itself, I believe the concept is immensely useful, as it allows you to write strongly typed code where you wouldn't be able to otherwise. But I agree that, broadly speaking, C++ approach to this is messy.
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