tree fd0a7c39e8ff11ec9dabc400f678899b70b941a2
parent 24b9672ddc4f52beb7487f981a76c62a6cfd791d
author Primiano Tucci <primiano@google.com> 1509450632 +0000
committer Primiano Tucci <primiano@google.com> 1509450822 +0000

Use custom libcxx by default on Linux and fix sanitizers

This CL:
 - switches Linux to libcxx by default.
 - turns libcxx into a DSO for sanitizers.
 - fixes a bunch of sanitizers build files.
 - enables the sanitizers cross-checks on the CI.

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 /buildtools version of libcxx:
1) Sanitizers requires that the c++ library is built from sources, see
   https://github.com/google/sanitizers/wiki/MemorySanitizerLibcxxHowTo.
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).

Bug: 68256752
Change-Id: I70a99351cff6582663101bf26583f20460076013