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POGlobal const initializing and difference between constructor in .h or .cpp file
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  1. POGlobal const initializing and difference between constructor in .h or .cpp file
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    copied!<p>I was wondering why sometimes my global const defined in seperate .h file isn't properly initialized when I need it. Some tests lead me to situation that I can't understand. I don't know how to explain it, so here's the code:</p> <h3>main.cpp</h3> <pre><code>#include &lt;iostream&gt; #include "class.h" using namespace std; A a; B b; int main(int argc, char* argv[]){ A aa; B bb; cout&lt;&lt;a.a&lt;&lt;" "&lt;&lt;aa.a&lt;&lt;endl; cout&lt;&lt;b.b&lt;&lt;" "&lt;&lt;bb.b&lt;&lt;endl; return 0; } </code></pre> <h3>class.h</h3> <pre><code>#ifndef CLASS_H #define CLASS_H #include "const.h" class A { public: A(); float a; }; class B { public: B():b(CONST){} float b; }; #endif </code></pre> <h3>class.cpp</h3> <pre><code>#include "class.h" A::A() : a(CONST){} </code></pre> <h3>const.h</h3> <pre><code>#ifndef CONST_H #define CONST_H #include &lt;limits&gt; using namespace std; const float CONST = numeric_limits&lt;float&gt;::has_infinity ? -numeric_limits&lt;float&gt;::infinity() : -numeric_limits&lt;float&gt;::max(); #endif </code></pre> <p>After running above code I get:</p> <blockquote> <p>0 -1.#INF<br> -1.#INF -1.#INF</p> </blockquote> <p>when actually I would like to get 4 times '-1.#INF'. Why does it happen this way? If CONST would be '1' instead of above formula, it would work perfectly.</p> <p>I can "fix" it by making static getConst() method:</p> <pre><code>static float getConst(){ static const float CONST = numeric_limits&lt;float&gt;::has_infinity ? -numeric_limits&lt;float&gt;::infinity() : -numeric_limits&lt;float&gt;::max(); return CONST;} </code></pre> <p>but it just doesn't "feel" right. On other hand I just need two of those above... But maybe there's some other way?</p> <p>And, most importantly, why class B gets "right" CONST and class A don't?</p>
 

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