Support 'pub const BAR: &str = "hello world";'

[AxelNennker]

currently cbindgen does not support const &st
pub const BAR: &'static str = "hello world";

ignisvulpis@namenlos:~/development/cbindgen$ cbindgen -o /tmp/x.x tests/rust/constant.rs 
WARN: Skip constant::BAR - (Unhanded const definition)
ignisvulpis@namenlos:~/development/cbindgen$ 

I think that the bindings should be
#define BAR L"hello world" for C
and
static const wchar_t* BAR = L"hello world"; for C++

[eqrion]

Rust &'static str is not equivalent to C/C++ string literals. Rust string slices are represented as a (ptr, len). The ptr is to non-null terminated UTF-8 encoded characters. C/C++ string literals are just a ptr to a null-terminated ASCII or UTF-32 string.

It's possible to create constants on the C/C++ side that are similar to the Rust constants, but they wouldn't be able to passed over FFI unless they were wrapped somehow.

What do you need this functionality for?

[AxelNennker]

my pet project is https://github.com/hyperledger/indy-sdk/tree/master/libindy and when I run cbindgen there it produces a ton of warnings.
The project has a shared library with an C interface.
Which is here: https://github.com/hyperledger/indy-sdk/tree/master/libindy/src/api
Currently the C bindings for it were manually created. They are here:
https://github.com/hyperledger/indy-sdk/tree/master/libindy/include

I would like to produce them with cbindgen.

The constants are currently not exported but I think the should. Everything that comes through the API from C to Rust are C null terminated C 'strings'. The top API layer handles them.
https://github.com/hyperledger/indy-sdk/blob/master/libindy/src/utils/inmem_wallet.rs#L30
Some are de-serialized from JSON others are sent over the network. Currently users of the library create those constants manually. I want cbindgen to create them. The wrappers for different languages are here:
https://github.com/hyperledger/indy-sdk/tree/master/wrappers

This is the use case. I am not there where I want this to be.

[rlidwka]

Rust &'static str is not equivalent to C/C++ string literals.

Rust CStr is equivalent to C/C++ string literals.

So I've just opened an issue asking for that: #927