mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 21:50:14 +01:00
Chandler Carruth
c23230140d
This PR merges the OS-specific Clang flags into the main Clang flags features using feature-based constraints instead of separate features conditionally added. Similarly for libc++. This also move flags to more correctly live in the Clang flag set vs. the libc++ flag set as some of these flags were specific to using libc++. To make this change, the libc++ feature needs to be computed rather than being fixed, as we need to add search paths based on the installed location of LLVM and Clang. All of this only works when the OS-config flags work. The earlier PR adding these had a bug -- _none_ of the OS features would ever be enabled. This didn't result in a problem as the initial use was only to _disable_ flags on the wrong OS. Now that we're enabling flags, we have to get it right by marking all of these as `enabled`.
307 lines
11 KiB
Python
307 lines
11 KiB
Python
# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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# Exceptions. See /LICENSE for license information.
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# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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"""Definitions of general C++ `cc_toolchain_config` features."""
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load("@rules_cc//cc:action_names.bzl", "ACTION_NAMES")
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load(
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"@rules_cc//cc:cc_toolchain_config_lib.bzl",
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"feature",
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"flag_group",
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"flag_set",
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"with_feature_set",
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)
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load(
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":cc_toolchain_actions.bzl",
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"all_compile_actions",
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"all_cpp_compile_actions",
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"all_link_actions",
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"codegen_compile_actions",
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"preprocessor_compile_actions",
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)
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clang_feature = feature(
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name = "clang",
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enabled = True,
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flag_sets = [
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flag_set(
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actions = all_compile_actions + all_link_actions,
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flag_groups = [
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flag_group(flags = [
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"-no-canonical-prefixes",
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"-fcolor-diagnostics",
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]),
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flag_group(
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expand_if_available = "sysroot",
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flags = ["--sysroot=%{sysroot}"],
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),
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],
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),
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flag_set(
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actions = all_compile_actions,
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flag_groups = [
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flag_group(flags = [
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# Compile actions shouldn't link anything.
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"-c",
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]),
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# Flags controlling the production of specific outputs from
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# compile actions.
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flag_group(
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expand_if_available = "output_assembly_file",
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flags = ["-S"],
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),
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flag_group(
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expand_if_available = "output_preprocess_file",
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flags = ["-E"],
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),
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flag_group(
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expand_if_available = "dependency_file",
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flags = ["-MD", "-MF", "%{dependency_file}"],
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),
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flag_group(
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expand_if_available = "output_file",
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flags = ["-frandom-seed=%{output_file}"],
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),
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],
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),
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flag_set(
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# Flags specific to compiling C++ sources.
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actions = all_cpp_compile_actions,
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flag_groups = [flag_group(flags = [
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"-std=c++20",
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])],
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),
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flag_set(
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actions = codegen_compile_actions,
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flag_groups = [flag_group(flags = [
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"-ffunction-sections",
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"-fdata-sections",
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])],
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),
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flag_set(
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actions = codegen_compile_actions,
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flag_groups = [flag_group(
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expand_if_available = "pic",
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flags = ["-fPIC"],
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)],
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),
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flag_set(
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actions = preprocessor_compile_actions,
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flag_groups = [
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flag_group(flags = [
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# Disable a warning and override builtin macros to
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# ensure a hermetic build.
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"-Wno-builtin-macro-redefined",
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"-D__DATE__=\"redacted\"",
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"-D__TIMESTAMP__=\"redacted\"",
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"-D__TIME__=\"redacted\"",
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]),
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flag_group(
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flags = ["-D%{preprocessor_defines}"],
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iterate_over = "preprocessor_defines",
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),
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flag_group(
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expand_if_available = "includes",
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flags = ["-include", "%{includes}"],
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iterate_over = "includes",
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),
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flag_group(
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flags = ["-iquote", "%{quote_include_paths}"],
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iterate_over = "quote_include_paths",
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),
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flag_group(
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flags = ["-I%{include_paths}"],
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iterate_over = "include_paths",
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),
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flag_group(
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flags = ["-isystem", "%{system_include_paths}"],
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iterate_over = "system_include_paths",
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),
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],
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),
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flag_set(
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actions = [
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ACTION_NAMES.cpp_link_dynamic_library,
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ACTION_NAMES.cpp_link_nodeps_dynamic_library,
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],
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flag_groups = [flag_group(flags = ["-shared"])],
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),
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flag_set(
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actions = all_link_actions,
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flag_groups = [
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flag_group(
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expand_if_available = "strip_debug_symbols",
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flags = ["-Wl,-S"],
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),
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flag_group(
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expand_if_available = "library_search_directories",
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flags = ["-L%{library_search_directories}"],
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iterate_over = "library_search_directories",
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),
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flag_group(
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expand_if_available =
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"runtime_library_search_directories",
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iterate_over = "runtime_library_search_directories",
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flags = [
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"-Wl,-rpath,$ORIGIN/%{runtime_library_search_directories}",
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],
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),
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],
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),
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flag_set(
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actions = all_link_actions,
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flag_groups = [
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flag_group(
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flags = [
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"-fuse-ld=lld",
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# Force the C++ standard library and runtime libraries
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# to be statically linked. This works even with libc++
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# and libunwind despite the names, provided libc++ is
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# built with the CMake option:
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# - `-DCMAKE_POSITION_INDEPENDENT_CODE=ON`
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"-static-libstdc++",
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"-static-libgcc",
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# Link with Clang's runtime library. This is always
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# linked statically.
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"-rtlib=compiler-rt",
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# Link with pthread.
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"-lpthread",
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],
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),
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],
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with_features = [with_feature_set(["linux_target"])],
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),
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flag_set(
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actions = [ACTION_NAMES.cpp_link_executable],
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flag_groups = [flag_group(
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expand_if_available = "force_pic",
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flags = ["-pie"],
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)],
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with_features = [with_feature_set([
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"linux_target",
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"freebsd_target",
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])],
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),
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flag_set(
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actions = [ACTION_NAMES.cpp_link_executable],
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flag_groups = [flag_group(
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expand_if_available = "force_pic",
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flags = ["-fpie"],
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)],
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with_features = [with_feature_set(["macos_target"])],
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),
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],
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)
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clang_warnings_feature = feature(
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name = "clang_warnings",
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enabled = True,
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flag_sets = [flag_set(
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actions = all_compile_actions,
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flag_groups = [flag_group(flags = [
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"-Werror",
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"-Wall",
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"-Wextra",
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"-Wthread-safety",
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"-Wself-assign",
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"-Wimplicit-fallthrough",
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"-Wctad-maybe-unsupported",
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"-Wextra-semi",
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"-Wmissing-prototypes",
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"-Wzero-as-null-pointer-constant",
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"-Wdelete-non-virtual-dtor",
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# TODO: Regression that warns on anonymous unions; remove depending
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# on fix.
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"-Wno-missing-designated-field-initializers",
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])],
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)],
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)
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# Libc++ HARDENING_MODE has 4 possible values:
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# https://libcxx.llvm.org/Hardening.html#notes-for-users
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#
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# Do not enable DEBUG hardening mode, even for -c dbg, because its performance
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# impact on llvm-symbolizer is too severe -- this flag results in symbolization
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# becoming quadratic in the number of debug symbols, in practice meaning it
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# never completes.
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_libcpp_debug_flags = [
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"-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE",
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]
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_libcpp_release_flags = [
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"-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST",
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]
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def libcxx_feature(llvm_bindir = None, clang_bindir = None):
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"""Builds a libc++ feature.
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Returns:
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The feature for use with `cc_toolchain_config`.
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Args:
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llvm_bindir: Optional LLVM installation `bin` directory, causes the
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feature to look for adjacent installed libraries.
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clang_bindir: Optional Clang installation `bin` directory, causes the
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feature to look for adjacent installed libraries if different from
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`llvm_bindir`.
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"""
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# Explicitly add LLVM libs to the search path to preempt the
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# detected GCC installation's library paths. Those might have a
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# system installed libc++ and we want to find the one next to
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# our Clang.
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extra_link_flags = []
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if llvm_bindir:
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extra_link_flags.append("-L" + llvm_bindir + "/../lib")
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if clang_bindir and clang_bindir != llvm_bindir:
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extra_link_flags.append("-L" + clang_bindir + "/../lib")
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return feature(
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name = "libcxx",
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enabled = True,
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flag_sets = [
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flag_set(
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actions = all_cpp_compile_actions + all_link_actions,
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flag_groups = [flag_group(flags = [
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"-stdlib=libc++",
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])],
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with_features = [
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# libc++ is only used on non-Windows platforms.
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with_feature_set(not_features = ["windows_target"]),
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],
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),
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flag_set(
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actions = all_cpp_compile_actions,
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flag_groups = [flag_group(flags = _libcpp_debug_flags)],
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with_features = [with_feature_set(not_features = ["opt"])],
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),
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flag_set(
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actions = all_cpp_compile_actions,
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flag_groups = [flag_group(flags = _libcpp_release_flags)],
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with_features = [with_feature_set(features = ["opt"])],
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),
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flag_set(
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actions = all_link_actions,
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flag_groups = [flag_group(flags = [
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"-unwindlib=libunwind",
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])],
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with_features = [
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# libc++ is only used on non-Windows platforms.
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with_feature_set(not_features = ["windows_target"]),
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],
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),
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flag_set(
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actions = all_link_actions,
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flag_groups = [flag_group(flags = extra_link_flags + [
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# Force linking the static libc++abi archive here. This
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# *should* be linked automatically, but not every release of
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# LLVM correctly sets the CMake flags to do so.
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"-l:libc++abi.a",
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])],
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with_features = [with_feature_set(["linux_target"])],
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),
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],
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)
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