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FIX: Incorrect Code Generated With /Og and /Ob1

This article was previously published under Q218611
This article has been archived. It is offered "as is" and will no longer be updated.
Incorrect code is generated for a comparison such as
   if (!(i > 0))				
when it is compiled with both the /Og and /Ob1.
To work around the problem disable either the /Ob1 or /Og optimization.
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:
194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

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; }				

Article ID: 218611 - Last Review: 02/21/2014 00:33:59 - Revision: 2.0

Microsoft Visual C++ 6.0 Enterprise Edition, Microsoft Visual C++ 6.0 Professional Edition, Microsoft Visual C++, 32-bit Learning Edition 6.0

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