cbindgen   ![Build Status] ![Latest Version] ![Api Rustdoc]

This project can be used to generate C bindings for Rust code. It is currently being developed to support creating bindings for WebRender, but has been designed to support any project.

Features

• Builds bindings for a crate, its mods, its dependent crates, and their mods
• Only the necessary types for exposed functions are given bindings
• Can specify annotations for controlling some aspects of binding
• Support for generic structs
• Customizable formatting, can be used in C or C++ projects
• Support for generating #ifdef's for #[cfg] attributes

Use

Command line

cbindgen crate/ -o crate/bindings.h

See cbindgen --help for more options.

build.rs

cbindgen can also be used in build scripts. How this fits into compiling the native code depends on your project.

Here's an example build.rs script: ```rust extern crate cbindgen;

use std::env;

fn main() { let cratedir = env::var("CARGOMANIFEST_DIR").unwrap();

cbindgen::generate(&crate_dir)
  .unwrap()
  .write_to_file("bindings.h");

}

```

Configuration

There are some options that can be used to configure the binding generation. They can be specified by creating a cbindgen.toml with the options in the binding crate root or at a path manually specified through the command line. Alternatively, build scripts can specify them using cbindgen::generate_with_config.

Here is a description of the options available in a config.

```toml

An optional string of text to output at the beginning of the generated file

header = "/* Text to put at the beginning of the generated file. Probably a license. */"

An optional string of text to output at the end of the generated file

trailer = "/* Text to put at the end of the generated file */"

An optional name to use as an include guard

includeguard = "mozillawrbindingsh"

An optional string of text to output between major sections of the generated

file as a warning against manual editing

autogen_warning = "/* Warning, this file is autogenerated by cbindgen. Don't modify this manually. */"

Whether to include a comment with the version of cbindgen used to generate the

file

include_version = true

An optional namespace to output around the generated bindings

namespace = "ffi"

An optional list of namespaces to output around the generated bindings

namespaces = ["mozilla", "wr"]

The style to use for curly braces

braces = "[SameLine|NextLine]"

The desired length of a line to use when formatting lines

line_length = 80

The amount of spaces in a tab

tab_width = 2

The language to output bindings in

language = "[C|C++]"

[parse]

Whether to parse dependent crates and include their types in the generated

bindings

parse_deps = true

A white list of crate names that are allowed to be parsed

include = ["webrender", "webrender_traits"]

A black list of crate names that are not allowed to be parsed

exclude = ["libc"]

A list of crate names that should be run through cargo expand before

parsing to expand any macros

expand = ["euclid"]

[fn]

An optional prefix to put before every function declaration

prefix = "string"

An optional postfix to put after any function declaration

postfix = "string"

How to format function arguments

args = "[Auto|Vertical|Horizontal]"

A rule to use to rename function argument names

rename_args = "[None|GeckoCase|LowerCase|UpperCase|PascalCase|CamelCase|SnakeCase|ScreamingSnakeCase|QualifiedScreamingSnakeCase]"

[struct]

A rule to use to rename field names

rename_fields = "[None|GeckoCase|LowerCase|UpperCase|PascalCase|CamelCase|SnakeCase|ScreamingSnakeCase|QualifiedScreamingSnakeCase]"

Whether to generate helper template specialization for generics

generictemplatespecialization = true

Whether to derive an operator== for all structs

derive_eq = false

Whether to derive an operator!= for all structs

derive_neq = false

Whether to derive an operator< for all structs

derive_lt = false

Whether to derive an operator<= for all structs

derive_lte = false

Whether to derive an operator> for all structs

derive_gt = false

Whether to derive an operator>= for all structs

derive_gte = false

[enum]

A rule to use to rename enum variants

rename_variants = "[None|GeckoCase|LowerCase|UpperCase|PascalCase|CamelCase|SnakeCase|ScreamingSnakeCase|QualifiedScreamingSnakeCase]"

```

Examples

See compile-tests/ for some examples of rust source that can be handled.

Major differences between cbindgen and rusty-cheddar

1. cbindgen supports generics
2. cbindgen supports C++ output using enum class and template specialization
3. cbindgen supports generating bindings including multiple modules and crates

There may be other differences, but those are the ones that I know of. Please correct me if I misrepresented anything.

How it works

1. All the structs, enums, type aliases, and functions that are representable in C are gathered
2. A dependency graph is built using the extern "C" functions as roots
   • This removes unneeded types from the bindings and sorts the structs that depend on each other
3. Some code generation is done to specialize generics that are specified as type aliases
4. The items are printed in dependency order in C syntax

Future work

1. Better support for types with fully specified names
2. Support for generating a FFI interface for a Struct+Impl
3. ...