diff --git a/bazel/README.md b/bazel/README.md index 17e9264f66..dc849fd27a 100644 --- a/bazel/README.md +++ b/bazel/README.md @@ -2,40 +2,34 @@ ## Setup Instructions -1. Merge the `WORKSPACE` file in with your own at the root of your bazel -directory structure. If you don't have one, simply copy the file. -2. Merge the `bazelrc` file in with your `.bazelrc` file at the root of your -bazel directory structure. If you don't have one, simply copy the file and -rename it to `.bazelrc`. (Note the `.`) -3. Copy the `emscripten_toolchain` folder along with its contents to the root of -your bazel directory. - -Your directory structure should look like this: +In `WORKSPACE` file, put: ``` -bazel_root/ -├── .bazelrc -├── WORKSPACE -├── emscripten_toolchain/ -│ ├── BUILD.bazel -│ ├── builddefs.bzl -│ ├── crosstool.bzl -│ ├── emar.sh -│ ├── emcc.sh -│ ├── emcc_link.sh -│ ├── emscripten.BUILD -│ ├── emscripten_config -│ ├── env.sh -│ ├── link_wrapper.py -│ ├── wasm_binary.py -│ ├── wasm_cc_binary.bzl -│ ├── wasm_rules.bzl -├── your_project_folder/ -│ ├── your_project.file +load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") +http_archive( + name = "emsdk", + strip_prefix = "emsdk-c1589b55641787d55d53e883852035beea9aec3f/bazel", + url = "https://github.com/emscripten-core/emsdk/archive/c1589b55641787d55d53e883852035beea9aec3f.tar.gz", + sha256 = "7a58a9996b113d3e0675df30b5f17e28aa47de2e684a844f05394fe2f6f12e8e", +) + +load("@emsdk//:deps.bzl", emsdk_deps = "deps") +emsdk_deps() + +load("@emsdk//:emscripten_deps.bzl", emsdk_emscripten_deps = "emscripten_deps") +emsdk_emscripten_deps() ``` ## Building ### Using --config=wasm + +Put the following lines into your `.bazelrc`: +``` +build:wasm --crosstool_top=//emscripten_toolchain:everything +build:wasm --cpu=wasm +build:wasm --host_crosstool_top=@bazel_tools//tools/cpp:toolchain +``` + Simply pass `--config=wasm` when building a normal `cc_binary`. The result of this build will be a tar archive containing any files produced by emscripten. @@ -44,7 +38,7 @@ First, write a new rule wrapping your `cc_binary`. ``` load("@rules_cc//cc:defs.bzl", "cc_binary") -load("//emscripten_toolchain:wasm_rules.bzl", "wasm_cc_binary") +load("@emsdk//emscripten_toolchain:wasm_rules.bzl", "wasm_cc_binary") cc_binary( name = "hello-world", @@ -61,3 +55,7 @@ Now you can run `bazel build :hello-world-wasm`. The result of this build will be the individual files produced by emscripten. Note that some of these files may be empty. This is because bazel has no concept of optional outputs for rules. + +`wasm_cc_binary` uses transition to use emscripten toolchain on `cc_target` +and all of its dependencies, and does not require amending `.bazelrc`. This +is the preferred way, since it also unpacks the resulting tarball.