Error with static objects after assignment: sizeof delivers wrong result and dynamic method call is used

Original Reporter info from Mantis: Heinz.Dobler

• Reporter name: Heinz Dobler

Description:

Assume the following two types A and B:

 
TYPE
  A = OBJECT
    i: INTEGER;
    CONSTRUCTOR Init(i_par: INTEGER);
    PROCEDURE Write;
  END; (*OBJECT*)
  B = OBJECT(A)
    r: REAL;
    CONSTRUCTOR Init(i_par: INTEGER; r_par: REAL);
    PROCEDURE Write;
  END; (*OBJECT*)

and two variables (static objects) of these types:

  VAR
    sa: A;
    sb: B;

where SizeOf(sa) = 8 and SizeOf(sb) = 16.
After initialization with sa.Init(1) and sb.Init(2, 3.0), the assignment

sa := sb;

has the effect that SizeOf(sa) = 16. But 8 would be the correct result.

Even worse: when the two Write methods in A and B are declared VIRTUAL (to request dynamic binding), after the assignment above, the method call

sa.Write;

calls the Write method in class B which prints a non existing value for B.r.

Steps to reproduce:

To reproduce the Errors use the uploaded program OOP_Test.
1. For the SizeOf error:
   > fpc OOP_Test.pas
   > OOP_Test.exe
2. For the erroneous call of the Write method:
   Change line number 3 in OOP_Test.pas to 
     {$DEFINE VIRTUAL}
   then as above:
   > fpc OOP_Test.pas
   > OOP_Test.exe

Mantis conversion info:

• Mantis ID: 28153
• OS: Windows
• OS Build: Windwos 7 64 Bit
• Build: 2014/03/06, i386-win32
• Platform: Intel
• Version: 2.6.4