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POInline virtual function when called from another virtual function?
 

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  1. POInline virtual function when called from another virtual function?
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    <p>I have a class with two virtual member functions: <code>foo</code> and <code>wrapper</code>. <code>foo</code> is short and fast, and <code>wrapper</code> contains a loop that calls <code>foo</code> many times. My hope is that there is some way to inline the calls to <code>foo</code> <em>inside the wrapper function</em>, even when called from a pointer to an object:</p> <pre><code>MyClass *obj = getObject(); obj-&gt;foo(); // As I understand it, this cannot be inlined. That's okay. obj-&gt;wrapper(); // Nor will this. However, I hope that the machine code // for the wrapper function will contain inlined calls to // foo(). </code></pre> <p><strong>Essentially, I want the compiler to generate multiple versions of the wrapper function -- one for each possible class -- and inline calls to the appropriate <code>foo</code>, which should be possible since the object type is determined before picking which <code>wrapper</code> function to execute.</strong> Is this possible? Do any compilers support this optimization?</p> <p><strong>Edit:</strong> I appreciate all of the feedback and answers so far, and I may end up picking one of them. However, most responses ignore the last part of my question where I explain why I think this optimization should be feasible. That is really the crux of my question and I am still hoping someone can address that.</p> <p><strong>Edit 2</strong>: I picked Vlad's answer since he both suggested the popular workaround and partially addressed my proposed optimization (in the comments of David's answer). Thanks to everyone who wrote an answer -- I read them all and there wasn't a clear "winner".</p> <p>Also, I found an academic paper that proposes an optimization very similar to what I was suggesting: <a href="http://www.ebb.org/bkuhn/articles/cpp-opt.pdf" rel="nofollow">http://www.ebb.org/bkuhn/articles/cpp-opt.pdf</a>.</p>
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    1. COThe compiler will probably know enough to optimize the virtual function lookup into a one time hit.
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    2. COTrue, but that still leaves the (larger?) overhead of a non-inline function call, right?
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    3. COYes, but short of machine code instrumentation it's probably not possible to make this happen.
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