# 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") 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 custom_libcxx_is_static = !using_sanitizer } libcxx_prefix = "//buildtools/libcxx" libcxxabi_prefix = "//buildtools/libcxxabi"