61c35abc7a
It breaks @emsdk in workspaces that have this feature enabled.
The following error appears when using the latest commit:
cc_toolchain '@emsdk//emscripten_toolchain:everything' with
identifier 'emscripten-wasm' doesn't define a tool path for 'dwp'
The following error appears after adding `emdwp` tool and scripts:
output '*.dwo' was not created
Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Bazel Emscripten toolchain
Setup Instructions
In WORKSPACE file, put:
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "emsdk",
sha256 = "d55e3c73fc4f8d1fecb7aabe548de86bdb55080fe6b12ce593d63b8bade54567",
strip_prefix = "emsdk-3891e7b04bf8cbb3bc62758e9c575ae096a9a518/bazel",
url = "https://github.com/emscripten-core/emsdk/archive/3891e7b04bf8cbb3bc62758e9c575ae096a9a518.tar.gz",
)
load("@emsdk//:deps.bzl", emsdk_deps = "deps")
emsdk_deps()
load("@emsdk//:emscripten_deps.bzl", emsdk_emscripten_deps = "emscripten_deps")
emsdk_emscripten_deps(emscripten_version = "2.0.31")
The SHA1 hash in the above strip_prefix and url parameters correspond to the git revision of
emsdk 2.0.31. To get access to
newer versions, you'll need to update those. To make use of older versions, change the
parameter of emsdk_emscripten_deps(). Supported versions are listed in revisions.bzl
Building
Using wasm_cc_binary (preferred)
First, write a new rule wrapping your cc_binary.
load("@rules_cc//cc:defs.bzl", "cc_binary")
load("@emsdk//emscripten_toolchain:wasm_rules.bzl", "wasm_cc_binary")
cc_binary(
name = "hello-world",
srcs = ["hello-world.cc"],
)
wasm_cc_binary(
name = "hello-world-wasm",
cc_target = ":hello-world",
)
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.
See test_external/ for an example using embind.
Using --config=wasm
Put the following lines into your .bazelrc:
build:wasm --crosstool_top=@emsdk//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.
See the Bazel documentation
for more details