Determine Platform Affinity 32 bit, 64 bit or Any CPU for a Managed .NET PE

In my earlier post, I discussed how PEs in .NET can target different platforms and the subtle differences between them.
In this post, I’ll discuss how one can determine the platform (architecture) that a managed .NET PE targets.

For this, we’ll use a tool called CorFlags which come automatically installed with Visual Studio IDE. We’ll use the Visual Studio Developer Command Prompt to use this tool.

Syntax

CorFlags.exe assembly [options]

For more details on the options, refer to the MSDN link.

Now, based on the way in which the PE has been compiled, we can determine the platform affinity as follows:

CPU Architecture	PE	32BITREQ	32BITPREF
x86(32-bit)	PE32	1	0
x64(64-bit)	PE32+	0	0
Any CPU	PE32	0	0
Any CPU 32-bit preferred	PE32	0	1

The default case in Visual Studio IDE is Any CPU with 32-bit preferred.
Hence, if we run CorFlags tool in this case, we’ll get…

<code>E:\Dev\Projects\TestApp\TestApp\bin\Debug>corflags TestApp.exe
Microsoft (R) .NET Framework CorFlags Conversion Tool.  Version  4.6.1055.0
Copyright (c) Microsoft Corporation.  All rights reserved.

Version   : v4.0.30319
CLR Header: 2.5
PE        : PE32
CorFlags  : 0x20003
ILONLY    : 1
32BITREQ  : 0
32BITPREF : 1
Signed    : 0
</code>

As can be seen above, this is the case whereby the exe targets the default option of Any CPU with 32-bit preferred.

Similarly, as shown in the table, we can determine the platform affinity for other managed DLLs too.

Hope this was useful!

Abbreviations

PE: Process Executables (EXEs and DLLs)

References

• MSDN CorFlags.exe
• Code Project – Which Platform to Target your .NET Applications?
• SO-How to find if a native DLL file is compiled as x64 or x86?

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