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# Copyright 2022 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
# Several Rust codegen tools (bindgen, autocxx_gen) link against
# libclang. We prefer to distribute the static libraries that make up
# the conceptual "libclang", but there are quite a few such libraries.
# This script enumerates them.
import("//build/rust/rust_static_library.gni")
_clang_libs_dir = "//third_party/llvm-build/Release+Asserts/lib"
if (toolchain_has_rust) {
# This requires you to configure your .gclient file with
# "custom_vars": {
# "checkout_clang_libs": True,
# }
rust_static_library("clanglibs") {
crate_root = get_label_info(":find_clanglibs", "target_gen_dir") + "/lib.rs"
sources = [ crate_root ]
deps = [ ":find_clanglibs" ]
# all_dependent_configs not public_configs because these directives
# need to propagate to the eventual final linking step. Our immediate
# dependent is probably libclang_sys.rlib, which will only later be
# linked into an executable.
all_dependent_configs = [ ":clanglibs_static_config" ]
}
action("find_clanglibs") {
# We need to tell rustc to link such binaries against a large
# and frequently-varying list of static libraries.
# gn/ninja, however, require statically determined dependency
# rules.
# Our options are:
# a) hard-code them in a .gn file like this, changing them frequently;
# b) use exec_script to enumerate them. This will slow down everyone's
# 'gn' invocations
# c) use libclang.so instead
# d) put these files entirely outside the visibility of gn/ninja
# We choose option (d). We generate a crate which tells rustc to link
# against these things.
script = "find_clanglibs.py"
_generated_crate_root = "$target_gen_dir/lib.rs"
depfile = "$target_out_dir/find_clanglibs.d"
args = [
"--clang-libs-dir",
rebase_path(_clang_libs_dir),
"--output",
rebase_path(_generated_crate_root, root_build_dir),
"--depfile",
rebase_path(depfile, root_build_dir),
]
# Always rerun this script when clang rolls, in case the
# set of libraries has changed. The following script contains
# a clang revision label, so is guaranteed to change each time
# clang rolls.
inputs = [ rebase_path("//tools/clang/scripts/update.py") ]
outputs = [ _generated_crate_root ]
visibility = [ ":*" ]
}
config("clanglibs_static_config") {
# Inform dependent rustc invocations where these various libraries
# are to be found.
rustflags = [ "-L" + rebase_path(_clang_libs_dir) ]
# At present, all known Rust codegen tools are based ultimately
# on bindgen and libclang-sys, so set the environment variable
# required to inform those build processes where the libraries
# are.
rustenv = [ "LIBCLANG_STATIC_PATH=" + rebase_path(_clang_libs_dir) ]
}
}
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