x64 optimization bug in Visual Studio 2010

Question

Hi,

The following code produces incorrect output in Release x64 configuration:

#include <iostream>
#include <vector>

int wmain(int argc, wchar_t* argv[])
{
    std::vector<size_t> s;				/* 1 */

    size_t volatile three = 3;
    size_t volatile four = 4;

    size_t a = three;
    size_t b = four;

    if (a != b)
    {
        size_t n = std::min(a, b);		/* 2 */
        size_t x = std::max(a, b);

        std::cout << n << std::endl;
        std::cout << x << std::endl;
    }

    return 0;
}

Actual output: 4 4

Expected output: 3 4

If I remove line /* 1 */ or change /* 2 */ to a < b ? a : b; it works as expected.

Release Win32 works as expected.
Debug x64 works as expected.

Answer 1

Confirmed. The bug is in Visual Studio 2010 but has been fixed in Visual Studio 2012 RC.

Obviously, Microsoft must be aware of this but I suggest submitting a report anyway to http://connect.microsoft.com.

Answer 2

http://connect.microsoft.com allows only to submit bug reports for Visual Studio 2012 RC, not for 2010 or any other versions of Visual Studio.

Answer 3

I suggest using VS 2012 RC to address your problem. I don't hesitate to recommend VS 2012 RC for production use.

Answer 4

>I don't hesitate to recommend VS 2012 RC for production use.

Unless you need your application to run on Windows XP :)

Dave

Answer 5

Unless you need your application to run on Windows XP :)

At present, yes. However, so as not to mislead others, an update to Visual Studio 2012 will appear in the fall which will enable XP support.

Answer 6

Hi Igor Afanasyev,

If you are submitting feedback on Visual Studio 2010 and .NET Framework, please use the MS forums or contact MS support directly at http://support.microsoft.com or call 1-800-MICROSOFT.

See more details here: https://connect.microsoft.com/VisualStudio/content/content.aspx?ContentID=27774

Meanwhile, thanks for sharing your experience. It's a good reference for anyone else encounters same issue.

Best Regards,

Damon

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Damon Zheng [MSFT]
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