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POEmpty array declaration - strange compiler behavior
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  1. POEmpty array declaration - strange compiler behavior
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    copied!<p>I've found a strange looking piece of code in a project I have to maintain. There's an empty array member of a class which doesn't lead to an compiler error. I've tested some variations of such a code with MSVC 10.0:</p> <pre><code>template&lt;class T&gt; struct A { int i[]; }; // warning C4200: nonstandard extension used : zero-sized array in struct/union template&lt;class T&gt; struct B { static int i[]; }; template&lt;class T&gt; int B&lt;T&gt;::i[]; struct C { int i[]; }; //warning C4200: nonstandard extension used : zero-sized array in struct/union template&lt;class T&gt; struct D { static int i[]; }; template&lt;class T&gt; int D&lt;T&gt;::i[4]; template&lt;&gt; int D&lt;int&gt;::i[] = { 1 }; int main() { A&lt;void&gt; a; B&lt;void&gt; b; C c; D&lt;void&gt; d0; D&lt;int&gt; d1; a.i[0] = 0; // warning C4739: reference to variable 'a' exceeds its storage space b.i[0] = 0; // warning C4789: destination of memory copy is too small c.i[0] = 0; // warning C4739: reference to variable 'c' exceeds its storage space int i[]; // error C2133: 'i' : unknown size d0.i[0] = 0; // ok d0.i[1] = 0; // ok return 0; } </code></pre> <p>The error message at <code>int i[]</code> is absolutely sensible to me. The code which is shown with class <code>D</code> is well-formed standard C++. But what's about the classes <code>A</code>, <code>B</code> and <code>C</code>? What kind of types are the member variables <code>int i[]</code> in this classes?</p>
 

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