Knowledge Base

FIX: Error C1001: _asm Instruction Accessing Stack Using [ebp]

Article ID: 150572

Article Last Modified on 12/2/2003

APPLIES TO

This article was previously published under Q150572

SYMPTOMS

Inline assembly code that uses [ebp] to gain access to arguments or local variables on the stack results in this error:
fatal error C1001: INTERNAL COMPILER ERROR
(compiler file '\school.tp3\test\c10\src\P2\386\codegen.c', line 4040)

CAUSE

When an argument is passed to a function, or a local variable is declared in a function, the argument or variable is placed on the stack, and is already referenced in terms of [ebp]. When [ebp] is used explicitly to reference that argument or variable as in ccb[ebp], for example, the compiler adds [ebp] again, resulting in an illegal address. The compiler fails to catch this as a meaningful error, and instead generates error C1001.

RESOLUTION

Do not attempt to gain access to stack arguments or variables in terms of [ebp].

NOTE: In the sample code in this article, lcb[ebp] and ccb[ebp] are invalid references; lcb and ccb need to be referenced directly. Otherwise, the compiler does not catch the illegal reference.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

This problem was corrected in Microsoft Visual C++ 6.0 Service Pack 5.

MORE INFORMATION

Sample Code

/* Compile options needed:none
*/ 

#include <windows.h>

void masmfunc(DWORD ccb){

   _asm mov eax ,dword ptr ccb[ebp];   //C1001

//Or,
//  DWORD lcb = 20;

// _asm mov eax ,dword ptr lcb[ebp];   //C1001

}

Additional query words: kbVC400bug

Keywords: kbbug kbfix kbnoupdate kbcompiler KB150572


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