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POLinking error in dereferencing static variable
 

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  1. POLinking error in dereferencing static variable
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    <p>(I've failed to find any similar question... so, I hope you can help me)</p> <p>In a program in C++ that I'm developing, I have a class that simulates a thread. I'll call it "Test" here. In it, I have an static map (<code>std::map</code>, from STL) that in which I store some semaphores (because I need all of the threads to have access to the same semaphores). (I think it is not worth to explain why I'm using a <code>map</code>, instead of a <code>vector</code>, but I believe this shouldn't be a problem)</p> <p>To "get" this static variable, I created a <code>getMutexHash()</code> function, that returns a pointer to the static <code>map</code>. But, for some reason, after compiling, I'm getting a linker error when trying to return a <code>this pointer</code>.</p> <p>The following code exemplifies the problem:</p> <pre class="lang-cpp prettyprint-override"><code>// MAIN.CPP #include "Test.h" int main () { Test test; map&lt;int, pthread_mutex_t&gt;* mutexHash = test.getMutexHash(); return 0; } // TEST.H #include &lt;map&gt; #include &lt;pthread.h&gt; using namespace std; class Test { public: map&lt;int, pthread_mutex_t&gt;* getMutexHash(); private: static map&lt;int, pthread_mutex_t&gt; mutexHash; }; // TEST.CPP #include "Test.h" map&lt;int, pthread_mutex_t&gt;* Test::getMutexHash() { return &amp;mutexHash; } </code></pre> <p>When compiling, I get no error nor warnings; but when linking, I receive this error:</p> <pre><code>Test.o: In function `Test::getMutexHash()': Test.cpp:(.text+0x9): undefined reference to `Test::mutexHash' collect2: ld returned 1 exit status </code></pre> <p>Can someone help me?</p>
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    1. COpossible duplicate of [Undefined reference to a static member of the class](http://stackoverflow.com/questions/8380289/undefined-reference-to-a-static-member-of-the-class)
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