BUG: C2443 Using Structure Member Operand in _asm Block

• The Microsoft C/C++ Compiler (CL.EXE), included with: - Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51 - Microsoft Visual C++, 32-bit Edition, versions 1.1, 2.0, 2.1, 4.0,

       4.1, 4.2, 5.0 on the following platform:
       - x86
  

SYMPTOMS

Under the four conditions described in this article, the following compiler error is generated:

   test.cpp(linenumber) : error C2443: operand size conflict

• You're using inline assembly.
• The size of the source operand on an assembly instruction is different from the size of the destination operand.
• The source operand is a member of a structure.
• The PTR operator is used to force the operand to the size required.

RESOLUTION

If you are using C++, declare a reference variable initialized with the structure member. Use the reference variable as the source operand in the assembly instruction as shown in this sample code:

Sample Code

   /* Compile options needed: /Tp
   */

   struct Test
   {
     int  nInt;
   } test1;

   void main(void)
   {
   __asm  mov  bh, BYTE PTR test1.nInt  /* error occurs here */

   int & nTest = test1.nInt;   /*  these lines work  */

   __asm  mov  bh, BYTE PTR nTest   /*  these lines work  */
   }

STATUS