Linker errors for 32-bit msvc builds

[dherman]

I've run into linker errors trying to use os_info::get() in 32-bit Windows (MSVC) builds. I wrote a minimal example that demonstrates the failure, and included an appveyor project so you can see the full output with the error.

Here's the minimal example code, and here's the Appveyor output.

Hope this is helpful!

[dherman]

For a bit more context, the linker error is failing to find __imp__RtlGetVersion. I'm a little bit baffled a) at the name mangling and b) that it can't find RtlGetVersion since the link command includes ntdll.lib, which is supposedly the library that contains that symbol. But I'm not an expert at Windows linking so I'm sort of stretching my limitations here. :)

[retep998]

The dllimport name mangling is not the issue. The issue is actually that the wrong calling convention is being used.

https://github.com/DarkEld3r/os_info/blob/4f7106f8729e169dfbe08027e9d93a6f083ba831/src/windows/winapi.rs#L35-L38

You want to be using extern "system" for Windows API functions, not extern "C".

[dherman]

Yay! I'll create a PR right now.