Cargo C-ABI helpers

Crates.io

cargo applet to build and install C-ABI compatibile 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.

Usage

``` sh

build the library, create the .h header, create the .pc file

$ cargo cbuild --destdir=${D} --prefix=/usr --libdir=/usr/lib64 sh

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:

Create a capi.rs with the C-API you want to expose and use #[cfg(cargo_c)] 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.
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.

Advanced

You may override various aspects of cargo-c via settings in Cargo.toml under the package.metadata.capi key

```toml [package.metadata.capi]

Configures the minimum required cargo-c version. Trying to run with an

older version causes an error.

min_version = "0.6.10" ```

Header Generation

```toml [package.metadata.capi.header]

Used as header file name. By default this is equal to the crate name.

The name can be with or without the header filename extension `.h`

name = "new_name"

Install the header into a subdirectory with the name of the crate. This

is enabled by default

subdirectory = true

Generate the header file with `cbindgen`, or copy a pre-generated header

from the `assets` subdirectory. By default a header is generated.

generation = true ```

`pkg-config` File Generation

```toml [package.metadata.capi.pkg_config]

Used as the package name in the pkg-config file and defaults to the crate name.

name = "libfoo"

Used as the package description in the pkg-config file and defaults to the crate description.

description = "some description"

Used as the package version in the pkg-config file and defaults to the crate version.

version = "1.2.3" ```

Library Generation

```toml [package.metadata.capi.library]

Used as the library name and defaults to the crate name. This might get

prefixed with `lib` depending on the target platform.