Investigate how to represent string constants

[retep998]

String constants currently aren't very useful as they do not have null terminators, and they are normal Rust UTF-8 strings. This means that users have to do runtime conversions in order to pass these strings to winapi functions, instead of just grabbing a raw pointer and tossing it in.

A solution needs to be found using a (procedural?) macro that will transform a string literal into a constant with methods to access both the UTF-8 and UTF-16 variants, both with and without a null terminator.

[MSxDOS]

I've implemented two ways, one using a decl macro + old proc_macro_derive for UTF16, and another using proc_macro_attribute for everything. I prefer the first one. L-like expression level macro for UTF16 literals may also be implemented if needed, I use it in my local projects. No external dependencies except for the separate crate for procedural macros. Target Rust is probably 1.31 (rust-lang/rust#53555 (comment))
Everything is here https://github.com/MSxDOS/string_const

[Eh2406]

There is also wstr that uses proc-macro-hack to do something similar on stable. I don't know if it has all the features we need.

[MSxDOS]

Besides having a lot of implicit dependencies, wstr uses encode_utf16 for everything and forces dynamic linking to std for some weird reason. Stable is also irrelevant here as either would require a version bump from 1.6 for procedural macros to work.

I don't know if it has all the features we need.

It obviously doesn't as it's just a simple expression level macro.

[suhr]

There are some relevant crates:

• https://docs.rs/wchar
• https://docs.rs/widestring

It is probably a good idea to combine them together, so you could have &'static U16CStr. There's an issue at widestring-rs: VoidStarKat/widestring-rs#11