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Extract C++-specific features into their own file (#6606)

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This leaves behind project-specific features such as the system header
management of our dependencies and the fancy cache management string.

No expected changes here, but yet another slightly different order of
flags.
This commit is contained in:
Chandler Carruth
2026-01-15 14:40:29 +00:00
committed by GitHub
parent 7a203efd18
commit 386a8a8a0b
4 changed files with 242 additions and 184 deletions
Download Patch File Download Diff File Expand all files Collapse all files
MODULE.bazel.lock
Generated
+1 -1
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@@ -252,7 +252,7 @@
"moduleExtensions": {
"//bazel/cc_toolchains:clang_configuration.bzl%clang_toolchain_extension": {
"general": {
"bzlTransitiveDigest": "ryYQP3j7NfvoUF+l/TDK6eiWjEfXgeBQSVVL+iS6hwc=",
"bzlTransitiveDigest": "MPw4EBs6afpwX0Xv1R3PmUjuOSQXbf9hi5tMqHjYz+M=",
"usagesDigest": "lTxkeAFhR0iBEa3dg5hWvtd2HFCr5zCJx/fl27A+IKA=",
"recordedFileInputs": {},
"recordedDirentsInputs": {},
bazel/cc_toolchains/cc_toolchain_cpp_features.bzl
+206
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@@ -0,0 +1,206 @@
# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
# Exceptions. See /LICENSE for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
"""Definitions of general C++ `cc_toolchain_config` features."""
load("@rules_cc//cc:action_names.bzl", "ACTION_NAMES")
load(
"@rules_cc//cc:cc_toolchain_config_lib.bzl",
"feature",
"flag_group",
"flag_set",
"with_feature_set",
)
load(
":cc_toolchain_actions.bzl",
"all_compile_actions",
"all_cpp_compile_actions",
"all_link_actions",
"codegen_compile_actions",
"preprocessor_compile_actions",
)
clang_feature = feature(
name = "clang",
enabled = True,
flag_sets = [
flag_set(
actions = all_compile_actions + all_link_actions,
flag_groups = [
flag_group(flags = [
"-no-canonical-prefixes",
"-fcolor-diagnostics",
]),
flag_group(
expand_if_available = "sysroot",
flags = ["--sysroot=%{sysroot}"],
),
],
),
flag_set(
actions = all_compile_actions,
flag_groups = [
flag_group(flags = [
# Compile actions shouldn't link anything.
"-c",
]),
# Flags controlling the production of specific outputs from
# compile actions.
flag_group(
expand_if_available = "output_assembly_file",
flags = ["-S"],
),
flag_group(
expand_if_available = "output_preprocess_file",
flags = ["-E"],
),
flag_group(
expand_if_available = "dependency_file",
flags = ["-MD", "-MF", "%{dependency_file}"],
),
flag_group(
expand_if_available = "output_file",
flags = ["-frandom-seed=%{output_file}"],
),
],
),
flag_set(
# Flags specific to compiling C++ sources.
actions = all_cpp_compile_actions,
flag_groups = [flag_group(flags = [
"-std=c++20",
])],
),
flag_set(
actions = codegen_compile_actions,
flag_groups = [flag_group(flags = [
"-ffunction-sections",
"-fdata-sections",
])],
),
flag_set(
actions = codegen_compile_actions,
flag_groups = [flag_group(
expand_if_available = "pic",
flags = ["-fPIC"],
)],
),
flag_set(
actions = preprocessor_compile_actions,
flag_groups = [
flag_group(flags = [
# Disable a warning and override builtin macros to
# ensure a hermetic build.
"-Wno-builtin-macro-redefined",
"-D__DATE__=\"redacted\"",
"-D__TIMESTAMP__=\"redacted\"",
"-D__TIME__=\"redacted\"",
]),
flag_group(
flags = ["-D%{preprocessor_defines}"],
iterate_over = "preprocessor_defines",
),
flag_group(
expand_if_available = "includes",
flags = ["-include", "%{includes}"],
iterate_over = "includes",
),
flag_group(
flags = ["-iquote", "%{quote_include_paths}"],
iterate_over = "quote_include_paths",
),
flag_group(
flags = ["-I%{include_paths}"],
iterate_over = "include_paths",
),
flag_group(
flags = ["-isystem", "%{system_include_paths}"],
iterate_over = "system_include_paths",
),
],
),
flag_set(
actions = [
ACTION_NAMES.cpp_link_dynamic_library,
ACTION_NAMES.cpp_link_nodeps_dynamic_library,
],
flag_groups = [flag_group(flags = ["-shared"])],
),
flag_set(
actions = all_link_actions,
flag_groups = [
flag_group(
expand_if_available = "strip_debug_symbols",
flags = ["-Wl,-S"],
),
flag_group(
expand_if_available = "library_search_directories",
flags = ["-L%{library_search_directories}"],
iterate_over = "library_search_directories",
),
flag_group(
expand_if_available =
"runtime_library_search_directories",
iterate_over = "runtime_library_search_directories",
flags = [
"-Wl,-rpath,$ORIGIN/%{runtime_library_search_directories}",
],
),
],
),
],
)
clang_warnings_feature = feature(
name = "clang_warnings",
enabled = True,
flag_sets = [flag_set(
actions = all_compile_actions,
flag_groups = [flag_group(flags = [
"-Werror",
"-Wall",
"-Wextra",
"-Wthread-safety",
"-Wself-assign",
"-Wimplicit-fallthrough",
"-Wctad-maybe-unsupported",
"-Wextra-semi",
"-Wmissing-prototypes",
"-Wzero-as-null-pointer-constant",
"-Wdelete-non-virtual-dtor",
# TODO: Regression that warns on anonymous unions; remove depending
# on fix.
"-Wno-missing-designated-field-initializers",
])],
)],
)
libcxx_feature = feature(
name = "libcxx",
enabled = True,
flag_sets = [
flag_set(
actions = all_cpp_compile_actions + all_link_actions,
flag_groups = [flag_group(flags = [
"-stdlib=libc++",
])],
with_features = [
# libc++ is only used on non-Windows platforms.
with_feature_set(not_features = ["windows_target"]),
],
),
flag_set(
actions = all_link_actions,
flag_groups = [flag_group(flags = [
"-unwindlib=libunwind",
])],
with_features = [
# libc++ is only used on non-Windows platforms.
with_feature_set(not_features = ["windows_target"]),
],
),
],
)
bazel/cc_toolchains/clang_cc_toolchain_config.bzl
+34 -183
View File
@@ -18,9 +18,7 @@ load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
load(
":cc_toolchain_actions.bzl",
"all_compile_actions",
"all_cpp_compile_actions",
"all_link_actions",
"codegen_compile_actions",
"preprocessor_compile_actions",
)
load(
@@ -30,6 +28,12 @@ load(
"user_flags_feature",
)
load(":cc_toolchain_config_features.bzl", "target_os_features")
load(
":cc_toolchain_cpp_features.bzl",
"clang_feature",
"clang_warnings_feature",
"libcxx_feature",
)
load(":cc_toolchain_debugging.bzl", "debugging_features")
load(
":cc_toolchain_linking.bzl",
@@ -66,197 +70,37 @@ load(
)
def _build_features(ctx):
# TODO: Refactor this into a reusable form in its own file.
default_flags_feature = feature(
name = "default_flags",
project_flags_feature = feature(
name = "project_flags",
enabled = True,
flag_sets = [
flag_set(
actions = all_compile_actions + all_link_actions,
flag_groups = [
flag_group(flags = [
"-no-canonical-prefixes",
"-fcolor-diagnostics",
]),
flag_group(
expand_if_available = "sysroot",
flags = ["--sysroot=%{sysroot}"],
),
],
),
flag_set(
actions = all_compile_actions,
flag_groups = [
# First, flags for all compiles, regardless of output.
flag_group(flags = [
"-Werror",
"-Wall",
"-Wextra",
"-Wthread-safety",
"-Wself-assign",
"-Wimplicit-fallthrough",
"-Wctad-maybe-unsupported",
"-Wextra-semi",
"-Wmissing-prototypes",
"-Wzero-as-null-pointer-constant",
"-Wdelete-non-virtual-dtor",
# TODO: Regression that warns on anonymous unions;
# remove depending on fix.
"-Wno-missing-designated-field-initializers",
# Don't warn on external code as we can't
# necessarily patch it easily. Note that these have
# to be initial directories in the `#include` line.
"--system-header-prefix=absl/",
"--system-header-prefix=benchmark/",
"--system-header-prefix=boost/",
"--system-header-prefix=clang-tools-extra/",
"--system-header-prefix=clang/",
"--system-header-prefix=gmock/",
"--system-header-prefix=gtest/",
"--system-header-prefix=libfuzzer/",
"--system-header-prefix=llvm/",
"--system-header-prefix=re2/",
"--system-header-prefix=tools/cpp/",
"--system-header-prefix=tree_sitter/",
# Compile actions shouldn't link anything.
"-c",
]),
# Flags controlling the production of specific outputs from
# compile actions.
flag_group(
expand_if_available = "output_assembly_file",
flags = ["-S"],
),
flag_group(
expand_if_available = "output_preprocess_file",
flags = ["-E"],
),
flag_group(
expand_if_available = "dependency_file",
flags = ["-MD", "-MF", "%{dependency_file}"],
),
flag_group(
expand_if_available = "output_file",
flags = ["-frandom-seed=%{output_file}"],
),
],
),
flag_set(
# Flags specific to compiling C++ source.
actions = all_cpp_compile_actions,
flag_groups = [flag_group(flags = [
"-std=c++20",
# Don't warn on external code as we can't
# necessarily patch it easily. Note that these have
# to be initial directories in the `#include` line.
"--system-header-prefix=absl/",
"--system-header-prefix=benchmark/",
"--system-header-prefix=boost/",
"--system-header-prefix=clang-tools-extra/",
"--system-header-prefix=clang/",
"--system-header-prefix=gmock/",
"--system-header-prefix=gtest/",
"--system-header-prefix=libfuzzer/",
"--system-header-prefix=llvm/",
"--system-header-prefix=re2/",
"--system-header-prefix=tools/cpp/",
"--system-header-prefix=tree_sitter/",
])],
),
flag_set(
actions = codegen_compile_actions,
flag_groups = [flag_group(flags = [
"-ffunction-sections",
"-fdata-sections",
])],
),
flag_set(
actions = codegen_compile_actions,
flag_groups = [flag_group(
expand_if_available = "pic",
flags = ["-fPIC"],
)],
),
flag_set(
actions = preprocessor_compile_actions,
flag_groups = [
flag_group(flags = [
# Disable a warning and override builtin macros to
# ensure a hermetic build.
"-Wno-builtin-macro-redefined",
"-D__DATE__=\"redacted\"",
"-D__TIMESTAMP__=\"redacted\"",
"-D__TIME__=\"redacted\"",
# Pass the clang version as a define so that bazel
# caching is more likely to notice version changes.
"-DCLANG_VERSION_FOR_CACHE=\"%s\"" % clang_version_for_cache,
]),
flag_group(
flags = ["-D%{preprocessor_defines}"],
iterate_over = "preprocessor_defines",
),
flag_group(
expand_if_available = "includes",
flags = ["-include", "%{includes}"],
iterate_over = "includes",
),
flag_group(
flags = ["-iquote", "%{quote_include_paths}"],
iterate_over = "quote_include_paths",
),
flag_group(
flags = ["-I%{include_paths}"],
iterate_over = "include_paths",
),
flag_group(
flags = ["-isystem", "%{system_include_paths}"],
iterate_over = "system_include_paths",
),
],
),
flag_set(
actions = [
ACTION_NAMES.cpp_link_dynamic_library,
ACTION_NAMES.cpp_link_nodeps_dynamic_library,
],
flag_groups = [flag_group(flags = ["-shared"])],
),
flag_set(
actions = all_link_actions,
flag_groups = [
flag_group(
expand_if_available = "strip_debug_symbols",
flags = ["-Wl,-S"],
),
flag_group(
expand_if_available = "library_search_directories",
flags = ["-L%{library_search_directories}"],
iterate_over = "library_search_directories",
),
flag_group(
expand_if_available =
"runtime_library_search_directories",
iterate_over = "runtime_library_search_directories",
flags = [
"-Wl,-rpath,$ORIGIN/%{runtime_library_search_directories}",
],
),
],
),
],
)
libcxx_feature = feature(
name = "libcxx",
enabled = True,
flag_sets = [
flag_set(
actions = all_cpp_compile_actions + all_link_actions,
flag_groups = [flag_group(flags = [
"-stdlib=libc++",
# Pass the Clang version to get better Bazel caching
# behavior with system-installed Clang binaries.
"-DCLANG_VERSION_FOR_CACHE=\"%s\"" % clang_version_for_cache,
])],
with_features = [
# libc++ is only used on non-Windows platforms.
with_feature_set(not_features = ["windows_target"]),
],
),
flag_set(
actions = all_link_actions,
flag_groups = [flag_group(flags = [
"-unwindlib=libunwind",
])],
with_features = [
# libc++ is only used on non-Windows platforms.
with_feature_set(not_features = ["windows_target"]),
],
),
],
)
@@ -389,8 +233,15 @@ def _build_features(ctx):
features += base_features
features += target_os_features(ctx.attr.target_os)
features += [
default_flags_feature,
# We always use Clang in the toolchain and enable all of its warnings.
clang_feature,
clang_warnings_feature,
# Enable libc++ where supported.
libcxx_feature,
# Include any project-specific flags, importantly after the Clang and
# warnings features so we can override as necessary here.
project_flags_feature,
]
features += sanitizer_features
bazel/cc_toolchains/clang_configuration.bzl
+1
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@@ -265,6 +265,7 @@ configure_clang_toolchain = repository_rule(
Label("//bazel/cc_toolchains:cc_toolchain_actions.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_base_features.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_config_features.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_cpp_features.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_debugging.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_linking.bzl"),
Label("//bazel/cc_toolchains:cc_toolchain_modules.bzl"),