docs/markdown/Rust-module.md

---
short-description: Rust language integration module
authors:
    - name: Dylan Baker
      email: dylan@pnwbakers.com
      years: [2020, 2021, 2022, 2024]
...

# Rust module

*(new in 0.57.0)*
*(Stable since 1.0.0)*

The rust module provides helper to integrate rust code into Meson. The
goal is to make using rust in Meson more pleasant, while still
remaining mesonic, this means that it attempts to make Rust work more
like Meson, rather than Meson work more like rust.

## Functions

### test()

```meson
rustmod.test(name, target, ...)
```

This function creates a new rust unittest target from an existing rust
based target, which may be a library or executable. It does this by
copying the sources and arguments passed to the original target and
adding the `--test` argument to the compilation, then creates a new
test target which calls that executable, using the rust test protocol.

This function takes two positional arguments, the first is the name of the
test and the second is the library or executable that is the rust based target.
It also takes the following keyword arguments:

- `dependencies`: a list of test-only Dependencies
- `link_with`: a list of additional build Targets to link with (*since 1.2.0*)
- `rust_args`: a list of extra arguments passed to the Rust compiler (*since 1.2.0*)

This function  also accepts all of the keyword arguments accepted by the
[[test]] function except `protocol`, it will set that automatically.

### bindgen()

This function wraps bindgen to simplify creating rust bindings around C
libraries. This has two advantages over invoking bindgen with a
`generator` or `custom_target`:

- It handles `include_directories`, so one doesn't have to manually convert them to `-I...`
- It automatically sets up a depfile, making the results more reliable
- It automatically handles assertions, synchronizing Rust and C/C++ to have the same behavior


It takes the following keyword arguments

- `input`: a list of Files, Strings, or CustomTargets. The first element is
  the header bindgen will parse, additional elements are dependencies.
- `output`: the name of the output rust file
- `output_inline_wrapper`: the name of the optional output c file containing
  wrappers for static inline function. This requires `bindgen-0.65` or
  newer (*since 1.3.0*).
- `include_directories`: A list of `include_directories` or `string` objects,
  these are passed to clang as `-I` arguments *(string since 1.0.0)*
- `c_args`: a list of string arguments to pass to clang untouched
- `args`: a list of string arguments to pass to `bindgen` untouched.
- `dependencies`: a list of `Dependency` objects to pass to the underlying clang call (*since 1.0.0*)
- `language`: A literal string value of `c` or `cpp`. When set this will force bindgen to treat a source as the given language. Defaults to checking based on the input file extension. *(since 1.4.0)*
- `bindgen_version`: a list of string version values. When set the found bindgen binary must conform to these constraints. *(since 1.4.0)*

```meson
rust = import('unstable-rust')

inc = include_directories('..'¸ '../../foo')

generated = rust.bindgen(
    input : 'myheader.h',
    output : 'generated.rs',
    include_directories : [inc, include_directories('foo')],
    args : ['--no-rustfmt-bindings'],
    c_args : ['-DFOO=1'],
)
```

If the header depends on generated headers, those headers must be passed to
`bindgen` as well to ensure proper dependency ordering, static headers do not
need to be passed, as a proper depfile is generated:

```meson
h1 = custom_target(...)
h2 = custom_target(...)

r1 = rust.bindgen(
  input : [h1, h2],  # h1 includes h2,
  output : 'out.rs',
)
```

*Since 1.1.0* Meson will synchronize assertions for Rust and C/C++  when the
`b_ndebug` option is set (via `-DNDEBUG` for C/C++, and `-C
debug-assertions=on` for Rust), and will pass `-DNDEBUG` as an extra argument
to clang. This allows for reliable wrapping of `-DNDEBUG` controlled behavior
with `#[cfg(debug_asserions)]` and or `cfg!()`. Before 1.1.0, assertions for Rust
were never turned on by Meson.

*Since 1.2.0* Additional arguments to pass to clang may be specified in a
*machine file in the properties section:

```ini
[properties]
bindgen_clang_arguments = ['-target', 'x86_64-linux-gnu']
```

### proc_macro()

```meson
rustmod.proc_macro(name, sources, ...)
```

*Since 1.3.0*

This function creates a Rust `proc-macro` crate, similar to:
```meson
[[shared_library]](name, sources,
  rust_crate_type: 'proc-macro',
  native: true)
```

`proc-macro` targets can be passed to `link_with` keyword argument of other Rust
targets.

Only a subset of [[shared_library]] keyword arguments are allowed:
- rust_args
- rust_dependency_map
- sources
- dependencies
- extra_files
- link_args
- link_depends
- link_with
- override_options