0a405bce   
   From: daniel.kruegler@googlemail.com   
      
   Am 09.11.2011 21:20, schrieb Vipin:   
   > I am seeing the following as an error by compiler. I remember it   
   > should be an error but want to know the concept behind it.   
      
   To make the problem statement more clear, I deliberately simplified your   
   example to   
      
   int Data[] = {0};   
      
   int main (){   
      sizeof Data/sizeof Data[0];   
      sizeof (int [])(&(Data[0]))/ sizeof Data[0];   
   }   
      
   The question is: Why is the second statement in main ill-formed?   
      
   The reason is some curiosity of the C++ language related to incomplete   
   types. To determine the size of some object or type, sizeof needs a   
   complete type. E.g. if you declare (but do not define=   
      
   class X;   
      
   the expression sizeof(X) is ill-formed, because the type X has not been   
   completely defined yet, so quiring sizeof cannot succeed.   
      
   We have a similar situation for a declaration of an array type without   
   bounds, like 'int[]'. Therefore testing the expression   
      
   sizeof(int[])   
      
   is also ill-formed, because sizeof has no information about the array   
   length.   
      
   The special situation is, when we have an array definition of the form   
      
   int Data[] = {0};   
      
   Here, the type of Data is incomplete until the closing brace, but after   
   the closing brace it is complete and has type int[1], because there is a   
   single element initializer.   
      
   Now writing a casting expression of the form   
      
   (int [])(&(Data[0])   
      
   is ill-formed for several reasons:   
      
   a) You cannot cast to an incomplete type   
   b) Even if we would write   
      
   (int[1])(&(Data[0]))   
      
   instead, this won't work, because arrays immediately undergo   
   array-to-pointer conversion unless directly bound to a reference to   
   array. The question anyway is, *why* you want to perform this code   
   transformation?   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
      
   --   
         [ See http://www.gotw.ca/resources/clcm.htm for info about ]   
         [ comp.lang.c++.moderated.    First time posters: Do this! ]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)