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How can a 32-bit program detect that it is launched in a 64-bit Windows?

, 21 Mar 2012 CPOL
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A 32-bit program can find out if it is launched in WoW64 with the help of the IsWow64Process function.

64-bit operating systems of the Windows family can execute 32-bit programs with the help of the WoW64 (Windows in Windows 64) subsystem that emulates the 32-bit environment due to an additional layer between a 32-bit application and 64-bit Windows API.

A 32-bit program can find out if it is launched in WoW64 with the help of the IsWow64Process function. The program can get additional information about the processor through the GetNativeSystemInfo function.

Keep in mind that the IsWow64Process function is included only in 64-bit Windows versions. You can use the GetProcAddress and GetModuleHandle functions to know if the IsWow64Process function is present in the system and to access it. This is an example demonstrating a correct use of the IsWow64Process function (download the project):

#include "stdafx.h"
bool IsWow64()
{
  BOOL bIsWow64 = FALSE;

  typedef BOOL (APIENTRY *LPFN_ISWOW64PROCESS)
    (HANDLE, PBOOL);

  LPFN_ISWOW64PROCESS fnIsWow64Process;

  HMODULE module = GetModuleHandle(_T("kernel32"));
  const char funcName[] = "IsWow64Process";
  fnIsWow64Process = (LPFN_ISWOW64PROCESS)
    GetProcAddress(module, funcName);

  if(NULL != fnIsWow64Process)
  {
    if (!fnIsWow64Process(GetCurrentProcess(),
                          &bIsWow64))
      throw std::exception("Unknown error");
  }
  return bIsWow64 != FALSE;
}

void main()
{
  if (IsWow64())
    printf("The process is running under WOW64.\n");
  else
    printf("The process is not running under WOW64.\n");

  printf("\nPress Enter to continue...");
  getchar();
}

References

  1. The Bereznikers. How to detect 64-bit OS
  2. MSDN Library. IsWow64Process Function

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Karpov Andrey
Architect Program Verification Systems, Co Ltd
Russian Federation Russian Federation

Andrey Karpov is technical manager of the OOO "Program Verification Systems" (Co Ltd) company developing the PVS-Studio tool which is a package of static code analyzers integrating into the Visual Studio development environment.

PVS-Studio is a static analyzer that detects errors in source code of C/C++ applications. There are 3 sets of rules included into PVS-Studio:

  1. Diagnosis of 64-bit errors (Viva64)
  2. Diagnosis of parallel errors (VivaMP)
  3. General-purpose diagnosis

Awards: MVP, Intel Black Belt

Andrey Karpov is also the author of many articles on the topic of 64-bit and parallel software development. To learn more about the PVS-Studio tool and sources concerning 64-bit and parallel software development, please visit the www.viva64.com site.

Best Articles:

My page on LinkedIn site: http://www.linkedin.com/pub/4/585/6a3

E-mail: karpov@viva64(dot)com

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Comments and Discussions

 
Questionmy vote 5 Pinmemberjeta54523-Mar-12 3:01 

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