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diff --git a/third_party/rust/cc/README.md b/third_party/rust/cc/README.md index 863540d2d9..33d4bb40f8 100644 --- a/third_party/rust/cc/README.md +++ b/third_party/rust/cc/README.md @@ -1,209 +1,13 @@ # cc-rs -A library to compile C/C++/assembly into a Rust library/application. - -[Documentation](https://docs.rs/cc) - -A simple library meant to be used as a build dependency with Cargo packages in -order to build a set of C/C++ files into a static archive. This crate calls out -to the most relevant compiler for a platform, for example using `cl` on MSVC. - -## Using cc-rs - -First, you'll want to both add a build script for your crate (`build.rs`) and -also add this crate to your `Cargo.toml` via: - -```toml -[build-dependencies] -cc = "1.0" -``` - -Next up, you'll want to write a build script like so: - -```rust,no_run -// build.rs - -fn main() { - cc::Build::new() - .file("foo.c") - .file("bar.c") - .compile("foo"); -} -``` - -And that's it! Running `cargo build` should take care of the rest and your Rust -application will now have the C files `foo.c` and `bar.c` compiled into a file -named `libfoo.a`. If the C files contain - -```c -void foo_function(void) { ... } -``` - -and - -```c -int32_t bar_function(int32_t x) { ... } -``` - -you can call them from Rust by declaring them in -your Rust code like so: - -```rust,no_run -extern { - fn foo_function(); - fn bar_function(x: i32) -> i32; -} - -pub fn call() { - unsafe { - foo_function(); - bar_function(42); - } -} - -fn main() { - // ... -} -``` - -See [the Rustonomicon](https://doc.rust-lang.org/nomicon/ffi.html) for more details. - -## External configuration via environment variables - -To control the programs and flags used for building, the builder can set a -number of different environment variables. - -* `CFLAGS` - a series of space separated flags passed to compilers. Note that - individual flags cannot currently contain spaces, so doing - something like: `-L=foo\ bar` is not possible. -* `CC` - the actual C compiler used. Note that this is used as an exact - executable name, so (for example) no extra flags can be passed inside - this variable, and the builder must ensure that there aren't any - trailing spaces. This compiler must understand the `-c` flag. For - certain `TARGET`s, it also is assumed to know about other flags (most - common is `-fPIC`). -* `AR` - the `ar` (archiver) executable to use to build the static library. -* `CRATE_CC_NO_DEFAULTS` - the default compiler flags may cause conflicts in some cross compiling scenarios. Setting this variable will disable the generation of default compiler flags. -* `CXX...` - see [C++ Support](#c-support). - -Each of these variables can also be supplied with certain prefixes and suffixes, -in the following prioritized order: - -1. `<var>_<target>` - for example, `CC_x86_64-unknown-linux-gnu` -2. `<var>_<target_with_underscores>` - for example, `CC_x86_64_unknown_linux_gnu` -3. `<build-kind>_<var>` - for example, `HOST_CC` or `TARGET_CFLAGS` -4. `<var>` - a plain `CC`, `AR` as above. - -If none of these variables exist, cc-rs uses built-in defaults - -In addition to the above optional environment variables, `cc-rs` has some -functions with hard requirements on some variables supplied by [cargo's -build-script driver][cargo] that it has the `TARGET`, `OUT_DIR`, `OPT_LEVEL`, -and `HOST` variables. - -[cargo]: https://doc.rust-lang.org/cargo/reference/build-scripts.html#inputs-to-the-build-script - -## Optional features - -### Parallel - -Currently cc-rs supports parallel compilation (think `make -jN`) but this -feature is turned off by default. To enable cc-rs to compile C/C++ in parallel, -you can change your dependency to: - -```toml -[build-dependencies] -cc = { version = "1.0", features = ["parallel"] } -``` - -By default cc-rs will limit parallelism to `$NUM_JOBS`, or if not present it -will limit it to the number of cpus on the machine. If you are using cargo, -use `-jN` option of `build`, `test` and `run` commands as `$NUM_JOBS` -is supplied by cargo. - -## Compile-time Requirements - -To work properly this crate needs access to a C compiler when the build script -is being run. This crate does not ship a C compiler with it. The compiler -required varies per platform, but there are three broad categories: - -* Unix platforms require `cc` to be the C compiler. This can be found by - installing cc/clang on Linux distributions and Xcode on macOS, for example. -* Windows platforms targeting MSVC (e.g. your target triple ends in `-msvc`) - require `cl.exe` to be available and in `PATH`. This is typically found in - standard Visual Studio installations and the `PATH` can be set up by running - the appropriate developer tools shell. -* Windows platforms targeting MinGW (e.g. your target triple ends in `-gnu`) - require `cc` to be available in `PATH`. We recommend the - [MinGW-w64](https://www.mingw-w64.org/) distribution, which is using the - [Win-builds](http://win-builds.org/) installation system. - You may also acquire it via - [MSYS2](https://www.msys2.org/), as explained [here][msys2-help]. Make sure - to install the appropriate architecture corresponding to your installation of - rustc. GCC from older [MinGW](http://www.mingw.org/) project is compatible - only with 32-bit rust compiler. - -[msys2-help]: https://github.com/rust-lang/rust#building-on-windows - -## C++ support - -`cc-rs` supports C++ libraries compilation by using the `cpp` method on -`Build`: - -```rust,no_run -fn main() { - cc::Build::new() - .cpp(true) // Switch to C++ library compilation. - .file("foo.cpp") - .compile("libfoo.a"); -} -``` - -For C++ libraries, the `CXX` and `CXXFLAGS` environment variables are used instead of `CC` and `CFLAGS`. - -The C++ standard library may be linked to the crate target. By default it's `libc++` for macOS, FreeBSD, and OpenBSD, `libc++_shared` for Android, nothing for MSVC, and `libstdc++` for anything else. It can be changed in one of two ways: - -1. by using the `cpp_link_stdlib` method on `Build`: - ```rust,no-run - fn main() { - cc::Build::new() - .cpp(true) - .file("foo.cpp") - .cpp_link_stdlib("stdc++") // use libstdc++ - .compile("libfoo.a"); - } - ``` -2. by setting the `CXXSTDLIB` environment variable. - -In particular, for Android you may want to [use `c++_static` if you have at most one shared library](https://developer.android.com/ndk/guides/cpp-support). - -Remember that C++ does name mangling so `extern "C"` might be required to enable Rust linker to find your functions. - -## CUDA C++ support - -`cc-rs` also supports compiling CUDA C++ libraries by using the `cuda` method -on `Build` (currently for GNU/Clang toolchains only): - -```rust,no_run -fn main() { - cc::Build::new() - // Switch to CUDA C++ library compilation using NVCC. - .cuda(true) - .cudart("static") - // Generate code for Maxwell (GTX 970, 980, 980 Ti, Titan X). - .flag("-gencode").flag("arch=compute_52,code=sm_52") - // Generate code for Maxwell (Jetson TX1). - .flag("-gencode").flag("arch=compute_53,code=sm_53") - // Generate code for Pascal (GTX 1070, 1080, 1080 Ti, Titan Xp). - .flag("-gencode").flag("arch=compute_61,code=sm_61") - // Generate code for Pascal (Tesla P100). - .flag("-gencode").flag("arch=compute_60,code=sm_60") - // Generate code for Pascal (Jetson TX2). - .flag("-gencode").flag("arch=compute_62,code=sm_62") - .file("bar.cu") - .compile("libbar.a"); -} -``` +A library for [Cargo build scripts](https://doc.rust-lang.org/cargo/reference/build-scripts.html) +to compile a set of C/C++/assembly/CUDA files into a static archive for Cargo +to link into the crate being built. This crate does not compile code itself; +it calls out to the default compiler for the platform. This crate will +automatically detect situations such as cross compilation and +various environment variables and will build code appropriately. + +Refer to the [documentation](https://docs.rs/cc) for detailed usage instructions. ## License |