Knowledge Base

FIX: C2443 Using Structure Member Operand in _asm Block

Article ID: 125799

Article Last Modified on 7/5/2005

APPLIES TO

This article was previously published under Q125799

SYMPTOMS

Under the four conditions described in this article, the following compiler error is generated:
test.cpp(linenumber) : error C2443: operand size conflict
Here linenumber is the assembly instruction in TEST.CPP file that meets the following conditions. This error occurs when the following four conditions are met:

  • 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
*/ 

truct 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  */ 
}
If you are using C, use a local variable instead of a reference variable.

STATUS

This bug was corrected in Microsoft Visual C++, version 6.0.

Additional query words: CPP CXX MASM assembler macro

Keywords: kbbug kbfix kbvc600fix KB125799


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