title: Why i can't watch the expression a[1][1] after declare it by a[n][n] in c++?
body: <p>my code:</p>
  
  <pre><code>#include &lt;iostream&gt;
  using namespace std;
  int main() {
      int n=5;
      int a[n][n];
      a[1][1]=5;
      return 0;
  }
  </code></pre>
  
  <p>I got this error when trying to watch the expression a[1][1] in eclipse on line 6:</p>
  
  <blockquote>
    <p>Failed to execute MI command:
    -data-evaluate-expression a[1][1] Error message from debugger back end:
    Cannot perform pointer math on
    incomplete types, try casting to a
    known type, or void *.</p>
  </blockquote>
  
  <p>i guess it's returned from gdb? however, i don't know why i can't watch that value? Isn't "a" is a normal multi-dimensional array?</p>