What is the purpose of the "Prefer 32-bit" setting in Visual Studio and how does it actually work?

c# .net visual-studio compilation cpu-architecture
Aaron picture Aaron · Aug 22, 2012 · Viewed 75.2k times · Source

Enter image description here

It is unclear to me how the compiler will automatically know to compile for 64-bit when it needs to. How does it know when it can confidently target 32-bit?

I am mainly curious about how the compiler knows which architecture to target when compiling. Does it analyze the code and make a decision based on what it finds?

Answer

Lex Li picture Lex Li · Aug 22, 2012

Microsoft has a blog entry What AnyCPU Really Means As Of .NET 4.5 and Visual Studio 11:

In .NET 4.5 and Visual Studio 11 the cheese has been moved. The default for most .NET projects is again AnyCPU, but there is more than one meaning to AnyCPU now. There is an additional sub-type of AnyCPU, “Any CPU 32-bit preferred”, which is the new default (overall, there are now five options for the /platform C# compiler switch: x86, Itanium, x64, anycpu, and anycpu32bitpreferred). When using the "Prefer 32-Bit" flavor of AnyCPU, the semantics are as follows:

  • 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.

Related questions

VS 2008 Professional, Smart Device .NET C# project - slow build

I have VS 2008 Professional and a Smart Device .NET C# project. I have ~100 cs files in total. The build takes a very long time, I have to wait for linker approx. 1min (60s) every time I compile the project. I …

Read More
How do I remedy "The breakpoint will not currently be hit. No symbols have been loaded for this document." warning?

A C# desktop application on the express edition worked, but then it didn't work 5 seconds later. I tried the following: Ensure debug configuration, debug flag, and full debug information are set on all assemblies. Delete all bin and obj folders …

Read More
The name 'ConfigurationManager' does not exist in the current context

I am trying to access connectionStrings from the config file. The code is ASP.NET + C#. I have added System.Configuration to reference and also mentioned with using. But still it wouldn't accept the assembly. I am using VSTS 2008. Any …

Read More