What does the “Prefer 32-bit” compiler flag mean for Visual Studio (C#, VB)?

Question

Just got the Visual Studio 11 developer preview installed. I see a new option in the project properties called "Prefer 32-bit" when compiling a managed (C#, VB) application with the AnyCPU target specified. This doesn't appear to be an option for class libraries, just top-level apps.

What does this flag indicate?

Answer 1

It likely indicates the app is AnyCpu but when 32 bit is available it shouold run as such. This makes sense - 64 bit apps use more memory, and sometimes you just dont need the memory space ;)

Answer 2

EDIT: Application compiled with "Any CPU 32-bit preferred" is compatible with x86, x64 and ARM, while x86 is compatible only with x86, x64 and not ARM. For details see this .

Answer 3

There is an good article at What AnyCPU Really Means As Of .NET 4.5 and Visual Studio 11 .

The short answer to your question is "When using that flavor of AnyCPU, the semantics are the following:

If the process runs on a 32-bit Windows system, it runs as a 32-bit process. IL is compiled to x86 machine code. If the process runs on a 64-bit Windows system, it runs as a 32-bit process. IL is compiled to x86 machine code. If the process runs on an ARM Windows system, it runs as a 32-bit process. IL is compiled to ARM machine code. The difference, then, between “Any CPU 32-bit preferred” and “x86” is only this: a .NET application compiled to x86 will fail to run on an ARM Windows system, but an “Any CPU 32-bit preferred” application will run successfully."

Answer 4

Here's right and simple answer: