The type of [CreateSymbolicLinkW](https://github.com/mozilla/rust/blob/6aad3bf944da209d1852c51144ba584de400a10c/src/libstd/libc.rs#L4106-L4108)'s return value is BOOLEAN and not BOOL. They have neither the same signedness nor size! Relevant links: [Windows Data Types](http://msdn.microsoft.com/en-us/library/windows/desktop/aa363866%28v=vs.85%29.aspx) [CreateSymbolicLink](http://msdn.microsoft.com/en-us/library/windows/desktop/aa383751%28v=vs.85%29.aspx)