The m4 macro processing language is commonly used as an intermediate format for text-based Unix development tools such as Bison and Flex.
This Bazel ruleset allows GNU M4 to be integrated into a Bazel build. It can
be used to perform macro expansion with the //m4:m4.bzl%m4 build rule, or as
a dependency in other rules via the Bazel toolchain system.
Currently, the only implementation of m4 supported by this ruleset is GNU M4.
API reference: docs/rules_m4.md
Add the following to your MODULE.bazel:
bazel_dep(name = "rules_m4", version = "0.2.3")To specify a version or build with additional C compiler options, use the
m4_repository_ext module extension:
m4 = use_extension(
"@rules_m4//m4/extensions:m4_repository_ext.bzl",
"m4_repository_ext",
)
m4.repository(
name = "m4",
version = "1.4.17",
extra_copts = ["-O3"],
)
use_repo(m4, "m4")
register_toolchains("@m4//:toolchain")Note that repository names registered with a given bzlmod module extension must be unique within the scope of that extension. See the Bazel module extensions documentation for more details.
Add the following to your WORKSPACE.bazel:
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "rules_m4",
# Obtain the package checksum from the release page:
# https://github.com/jmillikin/rules_m4/releases/tag/v0.2.3
sha256 = "",
urls = ["https://github.com/jmillikin/rules_m4/releases/download/v0.2.3/rules_m4-v0.2.3.tar.xz"],
)
load("@rules_m4//m4:m4.bzl", "m4_register_toolchains")
m4_register_toolchains(version = "1.4.18")To specify a version or build with additional C compiler options, use the
m4_repository and m4_toolchain_repository repository rules:
load("@rules_m4//m4:m4.bzl", "m4_repository", "m4_toolchain_repository")
m4_repository(
name = "m4_v1.4.17_fast",
version = "1.4.17",
extra_copts = ["-O3"],
)
m4_toolchain_repository(
name = "m4_toolchain_v1.4.17_fast",
m4_repository = "@m4_v1.4.17_fast",
)
register_toolchains("@m4_toolchain_v1.4.17_fast//:toolchain")Macro expansion with the //m4:m4.bzl%m4 build rule:
load("@rules_m4//m4:m4.bzl", "m4")
m4(
name = "hello_world",
srcs = ["hello_world.in.txt"],
output = "hello_world.txt",
)Macro expansion in a genrule:
genrule(
name = "hello_world_gen",
srcs = ["hello_world.in.txt"],
outs = ["hello_world_gen.txt"],
cmd = "$(M4) $(SRCS) > $@",
toolchains = ["@rules_m4//m4:current_m4_toolchain"],
)Writing a custom rule that depends on m4 as a toolchain:
load("@rules_m4//m4:m4.bzl", "M4_TOOLCHAIN_TYPE", "m4_toolchain")
def _my_rule(ctx):
m4 = m4_toolchain(ctx)
ctx.actions.run(
tools = [m4.m4_tool],
env = m4.m4_env,
# ...
)
my_rule = rule(
implementation = _my_rule,
toolchains = [M4_TOOLCHAIN_TYPE],
)
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