Bug#1132615: libc++1: Please enable LIBCXX_HARDENING_MODE=extensive or fast

[Andres Salomon]

Package: libc++1
Version: 1:22.1.2-1
Severity: wishlist

libc++ supports a hardening mode which is enabled at build time; it's 
the LIBCXX_HARDENING_MODE configuration in libcxx/CMakeLists.txt, and 
currently defaults to "none". Users of llvm's libc++ can define it for 
their own builds, and Chromium now requires its usage 
(_LIBCPP_HARDENING_MODE_EXTENSIVE) for security reasons. It would be 
nice if libc++ itself had one of the hardening modes enabled, too. I'm 
not sure whether "fast" or "extensive" is more appropriate.

More details about llvm's hardening here:
https://libcxx.llvm.org/Hardening.html

And here's where Chromium started requiring it due to a security hole 
that allowed escaping their v8 sandbox:
https://issues.chromium.org/issues/485696265