Re: compile error when initializing descendant struct

["Dave Bender" <codehero at gmail dot com>]

Mike,
   In C++, structs can be initialized in such a way: please see
section 5.7 in TC++PL.

 Although your solution is correct, I want to instantiate the structs
in reside in the .rodata section of the DSO,
which cannot be done by using the output of a function call.

Dave

On Wed, Apr 9, 2008 at 6:34 PM, Young, Michael <Michael.Young@paetec.com> wrote:
> Maybe I'm wrong, but this doesn't appear to be valid C++ to me... you're
>  using a construct that's normally used for array initialization - I
>  don't think it's valid for initializing an object (instead, use a ctor).
>  Object layout is not guaranteed to be the same as an "array" of the data
>  members (even if the members are the same datatype, except for perhaps
>  PODs), but even if it the same, I don't believe you can use array
>  initialization syntax just because the memory layout is the same.
>
>  Here's what I think you want to do:
>
>
>  struct A {
>   int x;
>  };
>
>  struct B : public A {
>
>   B( int arg_x, int arg_y ) : y( arg_y ) { x = arg_x ; }
>
>   int y;
>  };
>
>  const B b( 1, 2 );
>
>  I don't have g++ working on this machine at the moment, but this at
>  least compiles on another C++ compiler.
>  Note that you could also give A a ctor that initializes x, and then
>  initialize the base class in the initialization list of B ctor (instead
>  of doing the assignment of x in the body of B's ctor).
>
>  HTH,
>   Mike
>
>
>
>  -----Original Message-----
>  From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
>  Behalf Of Dave Bender
>  Sent: Wednesday, April 09, 2008 6:07 PM
>  To: gcc-help@gcc.gnu.org
>  Subject: compile error when initializing descendant struct
>
>  Dear list,
>   When I attempt to compile the following code (test2.cpp):
>
>
>  struct A {
>   int x;
>  };
>
>  struct B : public A {
>   int y;
>  };
>
>  const B b = {1, 2};
>
>
>  g++ gives the following error:
>
>  test2.cpp:9: error: scalar object 'b' requires one element in
>  initializer
>
>  My goal is to incorporate a large set of structs in a DSO (so that they
>  reside in the read only section). I don't see why this code should not
>  compile.
>
>  Thanks,
>  -Dave
>