BUG: IsBadStringPtr() Reports Bad String as Valid (111591)

SYMPTOMS

Under a particular condition, IsBadStringPtr() will report that a bad string is valid. If the pointer passed to IsBadStringPtr() refers to a block of memory of size 0xFFFF and is filled with all nonzero data, IsBadStringPtr() returns 0.

STATUS

Microsoft has confirmed this to be a bug in Windows version 3.1. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

For IsBadStringPtr() to validate a string, it must be passed a pointer to valid memory and the string must contain a NULL character that terminates the string.

The following code illustrates the error:

#include <windows.h>
#include <windowsx.h>
#include <memory.h>


LPSTR lpPtr;
BOOL fRet;

     // GlobalAllocPtr is a macro in WINDOWSX.H
lpPtr = GlobalAllocPtr(GMEM_MOVEABLE, 0XFFFF);

_fmemset(lpPtr, 'Q', 0xFFFF);

Ret = IsBadStringPtr(lpPtr, 0xFFFF);

if (fRet)  // ... etcetera, fRet incorrectly contains zero.