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POHow to force a static member to be initialized?
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  1. POHow to force a static member to be initialized?
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    copied!<p>Consider this example code:</p> <pre><code>template&lt;class D&gt; char register_(){ return D::get_dummy(); // static function } template&lt;class D&gt; struct Foo{ static char const dummy; }; template&lt;class D&gt; char const Foo&lt;D&gt;::dummy = register_&lt;D&gt;(); struct Bar : Foo&lt;Bar&gt; { static char const get_dummy() { return 42; } }; </code></pre> <p>(<a href="http://ideone.com/YuiG6" rel="nofollow noreferrer">Also on Ideone</a>.)</p> <p>I'd expect <code>dummy</code> to get initialized as soon as there is a concrete instantiation of <code>Foo</code>, which I have with <code>Bar</code>. <a href="https://stackoverflow.com/questions/1819131/c-static-member-initalization-template-fun-inside">This question</a> (and the standard quote at the end) explained pretty clear, why that's not happening.</p> <blockquote> <p>[...] in particular, the initialization (and any associated side-effects) of a static data member does not occur unless the static data member is itself used in a way that requires the definition of the static data member to exist.</p> </blockquote> <p>Is there any way to <em>force</em> <code>dummy</code> to be initialized (effectively calling <code>register_</code>) <em>without</em> any instance of <code>Bar</code> or <code>Foo</code> (no instances, so no constructor trickery) and without the user of <code>Foo</code> needing to explicitly state the member in some way? Extra cookies for not needing the derived class to do anything.</p> <hr> <p><strong>Edit</strong>: <a href="http://ideone.com/pTI77" rel="nofollow noreferrer">Found a way</a> with minimal impact on the derived class:</p> <pre><code>struct Bar : Foo&lt;Bar&gt; { // vvvvvvvvvvvv static char const get_dummy() { (void)dummy; return 42; } }; </code></pre> <p>Though, I'd still like the derived class not having to do that. :|</p>
 

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