Symptoms
Consider the following scenario:
-
You use Microsoft Visual Studio 2010 Service Pack 1 (SP1) to develop a Visual C++ application.
-
The source code of the application uses bitwise shift operators (<< or >>).
-
You build the application, targeting the x64 platform.
Note The /O2 or /Ox optimization option is enabled when you build the application. -
You run the application.
In this scenario, the bitwise shift operators may return incorrect results.
Resolution
Hotfix information
A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft website:
http://support.microsoft.com/contactus/?ws=supportNote In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.
Prerequisites
To apply this hotfix, you must have Visual Studio 2010 SP1 installed.
Restart requirement
You do not have to restart the computer after you install the hotfix if the affected files are not being used during the installation process. We recommend that you close all Visual Studio 2010-related components before you install the hotfix.
Hotfix replacement information
This hotfix does not replace any other hotfix.
File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
For all supported versions of Visual Studio 2010
|
File name |
File version |
File size |
Date |
Time |
Platform |
|---|---|---|---|---|---|
|
C2.dll |
16.0.40219.402 |
2,608,192 |
21-Jun-2012 |
19:08 |
x86 |
|
C2.dll |
16.0.40219.402 |
2,494,528 |
22-Jun-2012 |
16:00 |
x86 |
|
C2.dll |
16.0.40219.402 |
2,593,344 |
22-Jun-2012 |
16:00 |
x86 |
|
C2.dll |
16.0.40219.402 |
2,962,496 |
22-Jun-2012 |
16:00 |
x64 |
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More Information
For more information about Visual C++ /O options, go to the following MSDN website:
General information about /O optionsTo reproduce this issue, run a C++ application that uses the following code:
#include "stdafx.h"
typedef unsigned long long uint64;
void print(uint64 bitBoard)
{
printf("bitboard: %llu\n", bitBoard);
for (int i = 0 ; i < 1; i++)
{
// If either of the following two statements is commented out, the running results are correct.
printf("bitBoard before shift down: %llu\n", bitBoard);
bitBoard >>= 8;
}
}
int main()
{
for (int square = 31; square <= 32; square++)
{
printf("When square is: %d\n", square);
printf("\n(Case A):\n");
uint64 temp = uint64(1) << square;
print(temp);
printf("\n(Case B): \n");
print((uint64)(uint64(1LU) << square));
printf("\n(Case C):\n");
print((uint64)(uint64(1) << square));
printf("\n(Case D): \n");
print(1ULL << square);
// Workaround method is using the following statement instead.
//print(1ULL << (uint64)square);
printf("\n");
}
}
If you are affected by this issue, you receive a result that is different from the following expected result after you run the application:
When square is: 31
(Case A):
bitboard: 2147483648
bitBoard before shift down: 2147483648
(Case B):
bitboard: 2147483648
bitBoard before shift down: 2147483648
(Case C):
bitboard: 2147483648
bitBoard before shift down: 2147483648
(Case D):
bitboard: 2147483648
bitBoard before shift down: 2147483648
When square is: 32
(Case A):
bitboard: 4294967296
bitBoard before shift down: 4294967296
(Case B):
bitboard: 4294967296
bitBoard before shift down: 4294967296
(Case C):
bitboard: 4294967296
bitBoard before shift down: 4294967296
(Case D):
bitboard: 4294967296
bitBoard before shift down: 4294967296
