Q263609: BUG: Bad Code for Unsigned and Signed Comparisons with /Og

Article: Q263609
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s): 
Keyword(s): kbCodeGen kbCompiler kbVC600bug
Last Modified: 03-MAY-2001

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The information in this article applies to:

- The C/C++ Compiler (CL.EXE), included with:
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
   - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

The compiler may generate incorrect code for a signed comparison following an
unsigned same comparison when the /Og optimization is enabled.

Please refer to the sample code in the "More Information" section for details.

STATUS
======

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


MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

The following sample code demonstrates the bug:

  // Test.cpp
  // Compiler option needed: /Og
  #include <stdio.h>
  int a=-1;
  void main() {
  	if ((unsigned int)a > 5U) {
  		if (a > 5) {
  			printf("%d > 5\n", a);
  		} else {
  			printf("%d < 0\n", a);
  		}
  	} else {
  		printf("0 <= %d <= 5\n", a);
  	}
  }

Program Output:
-1 > 5

Additional query words:

======================================================================
Keywords          : kbCodeGen kbCompiler kbVC600bug 
Technology        : kbVCsearch kbAudDeveloper kbCVCComp
Version           : :6.0
Issue type        : kbbug

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