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POIs this a bug in GCC?
 

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  1. POIs this a bug in GCC?
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    <p>EDIT: This is not a bug, just me not knowing about <a href="https://stackoverflow.com/q/4643074/21475">dependent name lookups in templated base classes</a> (which MSVC "helpfully" resolves without errors).</p> <hr> <p>I wrote a functor implementation a while back, and a simple "Event" wrapper that uses it. It compiles fine under MSVC, but GCC gives an error about a member variable in the base class, <code>subscribers</code>, not being declared; changing <code>subscribers</code> to <code>this-&gt;subscribers</code> resolves the issue(!). It appears to happen only with the curiously recurring template pattern, and with partial template specialization.</p> <p>Simplified source (sorry for the mind-bending template usage...):</p> <pre><code>#include &lt;vector&gt; template&lt;typename TEvent&gt; struct EventBase { protected: std::vector&lt;int&gt; subscribers; }; template&lt;typename TArg1 = void, typename TArg2 = void&gt; struct Event : public EventBase&lt;Event&lt;TArg1, TArg2&gt; &gt; { void trigger(TArg1 arg1, TArg2 arg2) const { // Error on next line auto it = subscribers.cbegin(); } }; template&lt;typename TArg1&gt; struct Event&lt;TArg1, void&gt; : public EventBase&lt;Event&lt;TArg1&gt; &gt; { void trigger(TArg1 arg1) const { // Using `this` fixes error(?!) auto it = this-&gt;subscribers.cbegin(); } }; template&lt;&gt; struct Event&lt;void, void&gt; : public EventBase&lt;Event&lt;&gt; &gt; { void trigger() const { // No error here even without `this`, for some reason! auto it = subscribers.cbegin(); } }; int main() { return 0; } </code></pre> <p>Am I invoking undefined behaviour somewhere? Is my syntax somehow wrong? Is this really a bug in GCC? Is it perhaps a known bug? Any insight would be appreciated!</p> <p>More details: Compiled using <code>g++ -std=c++11 main.cpp</code>. I'm using GCC version 4.7.2. Exact error message:</p> <pre><code>main.cpp: In member function ‘void Event&lt;TArg1, TArg2&gt;::trigger(TArg1, TArg2) const’: main.cpp:17:15: error: ‘subscribers’ was not declared in this scope </code></pre>
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    1. COI've ran into this too. As a rule of thumb, if it involves templates, always trust gcc over msvc (I find that gcc is right 99.9 percent of the time).
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    2. CO@JesseGood There is even a duplicate [SO question](http://stackoverflow.com/q/11405/819272) from yet another MSVC refugee. Apparently, gcc fixed it somewhere in the 3.4 release, breaking some old code in the process. But hey, who said vendors need bug-compatibility as a selling point?
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