Article ID: 218611
Article Last Modified on 11/18/2003
APPLIES TO
- Microsoft Visual C++ 6.0 Enterprise Edition
- Microsoft Visual C++ 6.0 Professional Edition
- Microsoft Visual C++ 6.0 Standard Edition
This article was previously published under Q218611
SYMPTOMS
Incorrect code is generated for a comparison such as
if (!(i > 0))
when it is compiled with both the /Og and /Ob1.
RESOLUTION
To work around the problem disable either the /Ob1 or /Og optimization.
STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.
This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:
MORE INFORMATION
The following code is output.
i=7<BR/>
Error!<BR/><BR/>
It should output the following:
i=7<BR/>
i=6<BR/>
i=5<BR/>
i=4<BR/>
i=3<BR/>
i=2<BR/>
i=1<BR/>
i=0<BR/>
Steps to Reproduce Behavior
Compile the following code with /Og and /Ob1.
#include <stdio.h>
class C
{
public:
C(int i) { mLow = i; mHigh = 0; }
int getByte(int i) const;
unsigned long mLow;
unsigned long mHigh;
};
inline int C::getByte(int i) const
{
if (i < 4)
return (mLow >> (i << 3)) & 0xFF;
else
return (mHigh >> ((i - 4) << 3)) & 0xFF;
}
int main()
{
C h (1);
int i = 7;
for ( i = 7; ; i--) {
printf("i=%d\n",i);
if (h.getByte(i) != 0)
break;
if (!(i > 0)) { // Incorrect code
printf("Error!\n");
break;
}
}
return 1;
}
Keywords: kbbug kbfix kbvs600sp3fix KB218611
