Correct Way to Check If Windows Is 64 Bit or Not, on Runtime? (C++)

Correct way to check if Windows is 64 bit or not, on runtime? (C++)

Here's what Raymond Chen suggests in his blog at https://devblogs.microsoft.com/oldnewthing/20050201-00/?p=36553:

BOOL Is64BitWindows()
{
    #if defined(_WIN64)
        return TRUE;  // 64-bit programs run only on Win64
    #elif defined(_WIN32)
        // 32-bit programs run on both 32-bit and 64-bit Windows
        // so must sniff
        BOOL f64 = FALSE;
        return IsWow64Process(GetCurrentProcess(), &f64) && f64;
    #else
        return FALSE; // Win64 does not support Win16
    #endif
}

Detect 32-bit or 64-bit of Windows

The function to call is IsWow64Process or IsWow64Process2. It tells your 32-bit application if it is running on a 64 bit Windows.

If the program is compiled for 64 bits, it will already know.

How to check if the machine running on is 32 or 64 bit in C?

The obvious way to do this at run time.

#include <limits.h>
#include <stdio.h>

int main()
{
     printf("%d bits\n", (int)(CHAR_BIT * sizeof(void *)));
     return 0;
}

Technically, this is not 100% guaranteed to work. Practically, this will work with most modern compilers - it is unusual for a void pointer to be represented using a number of bits that differs from that of the underlying system architecture.

To do a compile time check, there is no standard way. It is necessary to resort to macros that are specific to your compiler/preprocessor. You will therefore need to read relevant documentation.

How to detect Windows 64-bit platform with .NET?

UPDATE: As Joel Coehoorn and others suggest, starting at .NET Framework 4.0, you can just check Environment.Is64BitOperatingSystem.

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IntPtr.Size won't return the correct value if running in 32-bit .NET Framework 2.0 on 64-bit Windows (it would return 32-bit).

As Microsoft's Raymond Chen describes, you have to first check if running in a 64-bit process (I think in .NET you can do so by checking IntPtr.Size), and if you are running in a 32-bit process, you still have to call the Win API function IsWow64Process. If this returns true, you are running in a 32-bit process on 64-bit Windows.

Microsoft's Raymond Chen:
How to detect programmatically whether you are running on 64-bit Windows

My solution:

static bool is64BitProcess = (IntPtr.Size == 8);
static bool is64BitOperatingSystem = is64BitProcess || InternalCheckIsWow64();

[DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool IsWow64Process(
    [In] IntPtr hProcess,
    [Out] out bool wow64Process
);

public static bool InternalCheckIsWow64()
{
    if ((Environment.OSVersion.Version.Major == 5 && Environment.OSVersion.Version.Minor >= 1) ||
        Environment.OSVersion.Version.Major >= 6)
    {
        using (Process p = Process.GetCurrentProcess())
        {
            bool retVal;
            if (!IsWow64Process(p.Handle, out retVal))
            {
                return false;
            }
            return retVal;
        }
    }
    else
    {
        return false;
    }
}

How to determine programmatically whether a particular process is 32-bit or 64-bit

One of the more interesting ways I've seen is this:

if (IntPtr.Size == 4)
{
    // 32-bit
}
else if (IntPtr.Size == 8)
{
    // 64-bit
}
else
{
    // The future is now!
}

To find out if OTHER processes are running in the 64-bit emulator (WOW64), use this code:

namespace Is64Bit
{
    using System;
    using System.ComponentModel;
    using System.Diagnostics;
    using System.Runtime.InteropServices;

    internal static class Program
    {
        private static void Main()
        {
            foreach (var p in Process.GetProcesses())
            {
                try
                {
                    Console.WriteLine(p.ProcessName + " is " + (p.IsWin64Emulator() ? string.Empty : "not ") + "32-bit");
                }
                catch (Win32Exception ex)
                {
                    if (ex.NativeErrorCode != 0x00000005)
                    {
                        throw;
                    }
                }
            }

            Console.ReadLine();
        }

        private static bool IsWin64Emulator(this Process process)
        {
            if ((Environment.OSVersion.Version.Major > 5)
                || ((Environment.OSVersion.Version.Major == 5) && (Environment.OSVersion.Version.Minor >= 1)))
            {
                bool retVal;

                return NativeMethods.IsWow64Process(process.Handle, out retVal) && retVal;
            }

            return false; // not on 64-bit Windows Emulator
        }
    }

    internal static class NativeMethods
    {
        [DllImport("kernel32.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi)]
        [return: MarshalAs(UnmanagedType.Bool)]
        internal static extern bool IsWow64Process([In] IntPtr process, [Out] out bool wow64Process);
    }
}

How to determine if the executing program was compiled for 64 bit?

Checking at run time if you are running a 64-bit application:

To see whether your process is 64-bit or 32-bit you can simply check the IntPtr.Size or any other pointer type. If you get 4 then you are running on 32-bit. If you get 8 then you are running on 64-bit.

What type of computer is your process running as:

You can check the PROCESSOR_ARCHITECTURE environment variable to see if you are running on an x64, ia64 or x86 machine.

Is your process running under emulation:

The Win32 API IsWow64Process will tell you if you are running a 32-bit application under x64. Wow64 means windows32 on windows64.

Contrary to what other people have posted: IsWow64Process will not tell you if you are running a 32-bit or a 64bit application. On 32-bit machines it will tell you FALSE for 32-bit applications when run, and on a 64-bit machine it will tell you TRUE for a 32-bit application. It only tells you if your application is running under emulation.

How can my program determine if it is running on 32-bit or 64-bit Windows?

How to detect Windows 64 bit platform with .net? might be helpful.

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