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Cargo C-ABI helpers

LICENSE Crates.io Build Status cargo-c chat dependency status

cargo applet to build and install C-ABI compatible dynamic and static libraries.

It produces and installs a correct pkg-config file, a static library and a dynamic library, and a C header to be used by any C (and C-compatible) software.

Installation

cargo-c may be installed from crates.io.

cargo install cargo-c

The rustc version supported is the same as the one supported by the cargo version embedded in the package version, or as set in the rust-version field.

You must have the cargo build requirements satisfied in order to build cargo-c:

  • git
  • pkg-config (on Unix, used to figure out the host-provided headers/libraries)
  • curl (on Unix)
  • OpenSSL headers (only for Unix, this is the libssl-dev package on deb-based distributions)

You may pass --features=vendored-openssl if you have problems building openssl-sys using the host-provided OpenSSL.

cargo install cargo-c --features=vendored-openssl

Usage

# build the library, create the .h header, create the .pc file
$ cargo cbuild --destdir=${D} --prefix=/usr --libdir=/usr/lib64
# build the library, create the .h header, create the .pc file, build and run the tests
$ cargo ctest
# build the library, create the .h header, create the .pc file and install all of it
$ cargo cinstall --destdir=${D} --prefix=/usr --libdir=/usr/lib64

For a more in-depth explanation of how cargo-c works and how to use it for your crates, read Building Crates so they Look Like C ABI Libraries.

The TL;DR:

This is the ideal setup for a project that wants to keep their C-API within the main crate:

  • Create a capi.rs with the C-API you want to expose and use #[cfg(cargo_c)]#[cfg(feature="capi")] to hide it when you build a normal rust library.
  • Make sure you have a lib target and if you are using a workspace the first member is the crate you want to export, that means that you might have to add a "." member at the start of the list.
  • Since Rust 1.38, also add "staticlib" to the "lib" crate-type. Do not specify the crate-type, cargo-c will add the correct library target by itself.
  • You may use the feature capi to add C-API-specific optional dependencies.

    NOTE: It must be always present in Cargo.toml

  • Remember to add a cbindgen.toml and fill it with at least the include guard and probably you want to set the language to C (it defaults to C++)
  • Once you are happy with the result update your documentation to tell the user to install cargo-c and do cargo cinstall --prefix=/usr --destdir=/tmp/some-place or something along those lines.

If you plan to keep the bindings as a separate crate and do not need to autogenerate the headers you may just populate Cargo.toml:

  • Add a capi feature, since it is used by cargo-c to identify packages that has to be built as C-libraries within a workspace.
  • Set the entry in package.metadata.capi.header.generation to false.
  • Optionally override the path to the header to a custom one instead of the default one.

Documentation

Users

Status

  • cli
    • build command
    • install command
    • test command
    • cargo applet support
  • build targets
    • pkg-config generation
    • header generation (cbindgen integration)
  • staticlib support
  • cdylib support
  • Generate version information in the header
    • Make it tunable
  • Extra Cargo.toml keys
  • Better status reporting

Availability

Packaging status

Acknowledgements

This software has been partially developed in the scope of the H2020 project SIFIS-Home with GA n. 952652.