[Mono-list] Question about Mono processor architecture reporting on ARM platforms

[Jonathan Pryor]

On Jan 29, 2015, at 3:33 AM, Alex J Lennon <ajlennon at dynamicdevices.co.uk> wrote:
> Can anybody advise if this is an implementational issue or if I'm doing something wrong here?

You're doing something wrong, *and* there's an implementation issue.

Module GetPEKind() returns information about the specified module, which can have absolutely no bearing on the actual runtime environment.

The C# compiler has a /platform:PLATFORM flag to specify the target platform:

	mcs /platform:x86 myapp.cs

This sets a flag in the PE header, and Module.GetPEKind() extracts this information. For example, build with /platform:arm, and Module.GetPEKind() will return ImageFileMachine.ARM *for that assembly*.

.NET checks this PE header value during process startup. For example, if you compile with /platform:anycpu, your app may run as a 32-bit process on 32-bit windows, and as a 64-bit process on 64-bit windows. If you need to run as a 32-bit process on 64-bit windows (e.g. because a dependent .dll you use is only 32-bit), then you must build your app with /platform:x86 to force .NET to run your app as a 32-bit process on 64-bit windows.

Mono ignores this PE header value. In the case of 32-bit vs. 64-bit processes, you must use an appropriately built mono (e.g. mono32 for a 32-bit mono) in order to get an appropriate bitness. (It's also entirely possible that there is no option; at present on OS X, the Mono package only provides a 32-bit runtime, though you can build a 64-bit runtime yourself.)

Offhand, short of using uname(3)/Mono.Unix.Native.Syscall.uname(), I'm not sure of a good way to determine the processor architecture.

 - Jon