This Bazel ruleset allows Flex to be integrated into a Bazel build. It can be used to generate lexical analyzers ("lexers") in C or C++.
API reference: docs/rules_flex.md
Add the following to your MODULE.bazel:
bazel_dep(name = "rules_flex", version = "0.4")To specify a version or build with additional C compiler options, use the
flex_repository_ext module extension:
flex = use_extension(
"@rules_flex//flex/extensions:flex_repository_ext.bzl",
"flex_repository_ext",
)
flex.repository(
name = "flex",
version = "2.6.4",
extra_copts = ["-O3"],
)
use_repo(flex, "flex")
register_toolchains("@flex//: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.
Integrating Flex into a C/C++ dependency graph:
load("@rules_flex//flex:flex.bzl", "flex_cc_library")
flex_cc_library(
name = "hello",
src = "hello.l",
)
cc_binary(
name = "hello_bin",
deps = [":hello"],
)Generating .c / .h / .cc source files (not as a CcInfo):
load("@rules_flex//flex:flex.bzl", "flex")
flex(
name = "hello_bin_srcs",
src = "hello.l",
)
cc_binary(
name = "hello_bin",
srcs = [":hello_bin_srcs"],
)Running Flex in a genrule:
genrule(
name = "hello_gen",
srcs = ["hello.l"],
outs = ["hello_gen.c"],
cmd = "M4=$(M4) $(FLEX) --outfile=$@ $<",
toolchains = [
"@rules_flex//flex:current_flex_toolchain",
"@rules_m4//m4:current_m4_toolchain",
],
)Writing a custom rule that depends on Flex as a toolchain:
load("@rules_flex//flex:flex.bzl", "FLEX_TOOLCHAIN_TYPE", "flex_toolchain")
load("@rules_m4//m4:m4.bzl", "M4_TOOLCHAIN_TYPE")
def _my_rule(ctx):
flex = flex_toolchain(ctx)
ctx.actions.run(
executable = flex.flex_tool,
env = flex.flex_env,
# ...
)
my_rule = rule(
implementation = _my_rule,
toolchains = [
FLEX_TOOLCHAIN_TYPE,
M4_TOOLCHAIN_TYPE,
],
)