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# `bindgen`
**`bindgen` automatically generates Rust FFI bindings to C (and some C++) libraries.**
For example, given the C header `doggo.h`:
```c
typedef struct Doggo {
int many;
char wow;
} Doggo;
void eleven_out_of_ten_majestic_af(Doggo* pupper);
```
`bindgen` produces Rust FFI code allowing you to call into the `doggo` library's
functions and use its types:
```rust
/* automatically generated by rust-bindgen 0.99.9 */
#[repr(C)]
pub struct Doggo {
pub many: ::std::os::raw::c_int,
pub wow: ::std::os::raw::c_char,
}
extern "C" {
pub fn eleven_out_of_ten_majestic_af(pupper: *mut Doggo);
}
```
## Users Guide
## MSRV
The `bindgen` minimum supported Rust version is **1.60.0**.
The `bindgen-cli` minimum supported Rust version is **1.64.0**.
No MSRV bump policy has been established yet, so MSRV may increase in any release.
The MSRV is the minimum Rust version that can be used to *compile* each crate. However, `bindgen` and `bindgen-cli` can generate bindings that are compatible with Rust versions below the current MSRV.
Most of the time, the `bindgen-cli` crate will have a more recent MSRV than `bindgen` as crates such as `clap` require it.
## API Reference
## Environment Variables
In addition to the [library API](https://docs.rs/bindgen) and [executable command-line API][bindgen-cmdline],
`bindgen` can be controlled through environment variables.
End-users should set these environment variables to modify `bindgen`'s behavior without modifying the source code of direct consumers of `bindgen`.
- `BINDGEN_EXTRA_CLANG_ARGS`: extra arguments to pass to `clang`
- Arguments are whitespace-separated
- Use shell-style quoting to pass through whitespace
- Examples:
- Specify alternate sysroot: `--sysroot=/path/to/sysroot`
- Add include search path with spaces: `-I"/path/with spaces"`
- `BINDGEN_EXTRA_CLANG_ARGS_<TARGET>`: similar to `BINDGEN_EXTRA_CLANG_ARGS`,
but used to set per-target arguments to pass to clang. Useful to set system include
directories in a target-specific way in cross-compilation environments with multiple targets.
Has precedence over `BINDGEN_EXTRA_CLANG_ARGS`.
Additionally, `bindgen` uses `libclang` to parse C and C++ header files.
To modify how `bindgen` searches for `libclang`, see the [`clang-sys` documentation][clang-sys-env].
For more details on how `bindgen` uses `libclang`, see the [`bindgen` users guide][bindgen-book-clang].
## Releases
We don't follow a specific release calendar, but if you need a release please
file an issue requesting that (ping `@emilio` for increased effectiveness).
## Contributing
[See `CONTRIBUTING.md` for hacking on `bindgen`!](./CONTRIBUTING.md)