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riot-sys

Bindings for RIOT system calls

This crate contains dynamically generated Rust FFI bindings to the RIOT Operating System.

Those bindings are inherently unsafe; it is recommended that their safe abstractions in the riot-wrappers crate are used in most applications.

RIOT integration

Which functions and structs are present in this crate, and sometimes their details, inherently depends on the RIOT configuration this will be used with. For example, RIOT's struct _thread only has a member name if DEVHELP is set for a build, and its flags member is only present if the thread_flags module is in use.

All the relevant information -- including the location of the actually used RIOT header files -- is contained in the RIOT environment variables CFLAGS_WITH_MACROS and INCLUDES; both need to be passed in to the Rust build system as a RIOT_CFLAGS environment variable.

In addition, riot-sys also needs to know the C compiler to properly expand the header files before transpilation; that information is passed in RIOT_CC.

When using riot-sys, it is usually easiest to run from a target within the Make system like this:

target/thumbv7m-none-eabi/debug/libmy_app.a: always
	CC= CFLAGS= CPPFLAGS= RIOT_CC="${CC}" RIOT_CFLAGS="$(CFLAGS_WITH_MACROS) $(INCLUDES)" cargo build --target thumbv7m-none-eabi

.PHONY: always

(CFLAGS etc. need to be cleared, for otherwise Cargo would assume those are host flags.)

The RIOT_CC and RIOT_CFLAGS are made available to dependent modules through Cargo; see riot-wrappers's build.sh for an example.

As an alternative to passing RIOT_CFLAGS and RIOT_CC, the path to a compile-commands.json file can be passed in RIOT_COMPILE_COMMANDS_JSON, with a RIOT_USEMODULES to go with it containing the list of used modules. The advantage of this approach is that on the RIOT side, LLVM-compativble CFLAGS are produced immaterial of which C compiler is used. Even when this alternative is used, the extracted CC and CFLAGS are still passed down to dependent crates as they were before. (The passed down CC will just always be clang).

Extension

Currently, only a subset of all the RIOT headers is processed; all the relevant header files are included in this crate's riot-headers.h header file. If you need access to more RIOT APIs, more includes can be added there.

External build dependencies

This crate's operation depends on C2Rust being installed. As right now some of the required fixes to C2Rust are not merged upstream yet, (and as it requires a particular nightly version), it should be installed like this:

$ git clone https://github.com/chrysn-pull-requests/c2rust/ -b for-riot
$ cd c2rust
$ rustup install nightly-2019-12-05
$ rustup component add --toolchain nightly-2019-12-05 rustfmt rustc-dev
$ cargo +nightly-2019-12-05 install --locked --debug --path c2rust

The main contents of this crate (ie. everything not in a module) is generated by bindgen.

Unlike the inline module (which contains the C2Rust transpilate), it is not moved into a dedicated linked module and reexported (in analogy to the inline), for that'd need explicit pub use linked::mutex_t etc for every type that's present in both and thus not imported for either. As long as this is inlined here, linked types (which are predominantly used so far) take precedence automatically.

License

This crate is licensed under the same terms as of the LGPL-2.1, following the license terms of the RIOT Operating System.