Re: how to compare the sizes of 2 structures at compile time

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From: Victor Bazarov (v.Abazarov_at_comAcast.net)
Date: 07/09/04 

Date: Fri, 09 Jul 2004 14:38:01 -0400

paul@slowmind.com wrote:
> I have 2 structures _test1 and _test2. At compile time, I want the compiler to issue an error if
> sizeof( _test1 ) != sizeof( _test2)

You can probably do it using templates:

   template<bool trueorfalse> struct If;
   template<> struct If<true> { enum { satisfied }; };
   template<> struct If<false> { enum { notsatisfied }; };

   int a, b;
   double c, d;

   int main()
   {
     If<sizeof(a) == sizeof(b)>::satisfied;
     If<sizeof(c) == sizeof(a)>::satisfied; // will get "satisfied" is not
                                            // a member" error message

     return 0;
   }

Should work for structs just as well.

Victor

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