README.md

# clang-sys

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Rust bindings for `libclang`.

If you are interested in a Rust wrapper for these bindings, see
[clang-rs](https://github.com/KyleMayes/clang-rs).

Supported on the stable, beta, and nightly Rust channels.<br/>
Minimum supported Rust version: **1.40.0**

Released under the Apache License 2.0.

## Documentation

There are two versions of the documentation, one for the API exposed when
linking dynamically or statically and one for the API exposed when linking at
runtime (see the
[Dependencies](https://github.com/KyleMayes/clang-sys#dependencies) section
of the README for more information on the linking options).

The only difference between the APIs exposed is that when linking at runtime a
few additional types and functions are exposed to manage the loaded `libclang`
shared library.

* Runtime - [Documentation](https://kylemayes.github.io/clang-sys/runtime/clang_sys)
* Dynamic / Static - [Documentation](https://kylemayes.github.io/clang-sys/default/clang_sys)

## Supported Versions

To target a version of `libclang`, enable one of the following Cargo features:

* `clang_3_5` - requires `libclang` 3.5 or later
* `clang_3_6` - requires `libclang` 3.6 or later
* `clang_3_7` - requires `libclang` 3.7 or later
* `clang_3_8` - requires `libclang` 3.8 or later
* `clang_3_9` - requires `libclang` 3.9 or later
* `clang_4_0` - requires `libclang` 4.0 or later
* `clang_5_0` - requires `libclang` 5.0 or later
* `clang_6_0` - requires `libclang` 6.0 or later
* `clang_7_0` - requires `libclang` 7.0 or later
* `clang_8_0` - requires `libclang` 8.0 or later
* `clang_9_0` - requires `libclang` 9.0 or later
* `clang_10_0` - requires `libclang` 10.0 or later
* `clang_11_0` - requires `libclang` 11.0 or later

If you do not enable one of these features, the API provided by `libclang` 3.5 will be available by
default.

## Dependencies

By default, this crate will attempt to link to `libclang` dynamically. In this case, this crate
depends on the `libclang` shared library (`libclang.so` on Linux, `libclang.dylib` on macOS,
`libclang.dll` on Windows). If you want to link to `libclang` statically instead, enable the
`static` Cargo feature. In this case, this crate depends on the LLVM and Clang static libraries. If
you don't want to link to `libclang` at compiletime but instead want to load it at runtime, enable
the `runtime` Cargo feature.

These libraries can be either be installed as a part of Clang or downloaded
[here](http://llvm.org/releases/download.html).

**Note:** The downloads for LLVM and Clang 3.8 and later do not include the `libclang.a` static
library. This means you cannot link to any of these versions of `libclang` statically unless you
build it from source.

### Versioned Dependencies

This crate supports finding versioned instances of `libclang.so` (e.g.,`libclang-3.9.so`).
In the case where there are multiple instances to choose from, this crate will prefer instances with
higher versions. For example, the following instances of `libclang.so` are listed in descending
order of preference:

1. `libclang-4.0.so`
2. `libclang-4.so`
3. `libclang-3.9.so`
4. `libclang-3.so`
5. `libclang.so`

**Note:** On BSD distributions, versioned instances of `libclang.so` matching the pattern
`libclang.so.*` (e.g., `libclang.so.7.0`) are also included.

**Note:** On Linux distributions when the `runtime` features is enabled, versioned instances of
`libclang.so` matching the pattern `libclang.so.*` (e.g., `libclang.so.1`) are also included.

## Environment Variables

The following environment variables, if set, are used by this crate to find the required libraries
and executables:

* `LLVM_CONFIG_PATH` **(compiletime)** - provides a full path to an `llvm-config` executable
  (including the executable itself [i.e., `/usr/local/bin/llvm-config-8.0`])
* `LIBCLANG_PATH` **(compiletime)** - provides a path to a directory containing a `libclang` shared
  library or a full path to a specific `libclang` shared library
* `LIBCLANG_STATIC_PATH` **(compiletime)** - provides a path to a directory containing LLVM and
  Clang static libraries
* `CLANG_PATH` **(runtime)** - provides a path to a `clang` executable

## Linking

### Dynamic

`libclang` shared libraries will be searched for in the following directories:

* the directory provided by the `LIBCLANG_PATH` environment variable
* the `bin` and `lib` directories in the directory provided by `llvm-config --libdir`
* the directories provided by `LD_LIBRARY_PATH` environment variable
* a list of likely directories for the target platform (e.g., `/usr/local/lib` on Linux)
* **macOS only:** the toolchain directory in the directory provided by `xcode-select --print-path`

On Linux, running an executable that has been dynamically linked to `libclang` may require you to
add a path to `libclang.so` to the `LD_LIBRARY_PATH` environment variable. The same is true on OS
X, except the `DYLD_LIBRARY_PATH` environment variable is used instead.

On Windows, running an executable that has been dynamically linked to `libclang` requires that
`libclang.dll` can be found by the executable at runtime. See
[here](https://msdn.microsoft.com/en-us/library/7d83bc18.aspx) for more information.

### Static

The availability of `llvm-config` is not optional for static linking. Ensure that an instance of
this executable can be found on your system's path or set the `LLVM_CONFIG_PATH` environment
variable. The required LLVM and Clang static libraries will be searched for in the same way as
shared libraries are searched for, except the `LIBCLANG_STATIC_PATH` environment variable is used in
place of the `LIBCLANG_PATH` environment variable.

### Runtime

The `clang_sys::load` function is used to load a `libclang` shared library for use in the thread in
which it is called. The `clang_sys::unload` function will unload the `libclang` shared library.
`clang_sys::load` searches for a `libclang` shared library in the same way one is searched for when
linking to `libclang` dynamically at compiletime.