blob: 52c1dac233ba38aa2a797e2d0f00c1854d0d0f5b [file] [log] [blame]
# Copyright (C) 2017 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import("//gn/standalone/sanitizers/sanitizers.gni")
import("//gn/standalone/wasm.gni")
declare_args() {
# Background:
# there are mainly two C++ libraries around in the world: (i) GNU's
# libstdc++ and LLVM's libc++ (aka libcxx). By default Linux provides libstdc++
# (even building with clang on Linux uses that by default) while Mac and
# Android switched to libcxx.
# buildtools/libcxx(abi) contains a fixed version of the libcxx, the same one
# that Chrome uses on most production configurations (% lagging catching up
# with our DEPS).
# The variable use_custom_libcxx tells our build system to prefer the
# aforementioned copy to the system one.
#
# Now, there are two reasons for using the checked in copy of libcxx:
# 1) LLVM sanitizers require that the c++ library is built from sources,
# because they need to be instrumented with -fsanitize as well (see
# https://github.com/google/sanitizers/wiki/MemorySanitizerLibcxxHowTo).
# On top of this, they also require that the c++ library is dynamically
# linked to prevent duplicate symbol errors when linking (see Chrome's
# build/config/c++/c++.gni)
# 2) The libstdc++ situation is too wild on Linux. Modern debian distros are
# fine but Ubuntu Trusty still ships a libstdc++ that doesn't fully
# support C++11. Hence we enable this flag on Linux by default.
# We still retain libstdc++ coverage on the Travis bots by overriding
# use_custom_libcxx=false when we target a modern library (see the
# GCC7 target in .travis.yml).
use_custom_libcxx = is_linux && is_clang && !is_wasm
custom_libcxx_is_static = !using_sanitizer
}
libcxx_prefix = "//buildtools/libcxx"
libcxxabi_prefix = "//buildtools/libcxxabi"