Maintaining boost cxx11abi packages

[springmeyer]

@tmpsantos (in #268) has figured out how to build cxx11abi packages for boost libraries on travis 🎉 .

The key is that we need to edit the headers of the libstdc++ installed to enable the "duel API":

sudo perl -i -p -e "s/# define _GLIBCXX_USE_DUAL_ABI 0/# define _GLIBCXX_USE_DUAL_ABI 1/g;" /usr/include/x86_64-linux-gnu/c++/5/bits/c++config.h

per #157 (comment)

Then one can set -D_GLIBCXX_USE_CXX11_ABI=1 and it is respected and will no longer default to 0.

Now we need to think through how to keep these maintained.

TODO:

• Does the boost new release script work?
  https://github.com/mapbox/mason/blob/master/utils/new_boost.sh
• Other existing cxx11abi packages need be ported to be built on travis (rather than manually pushed) (notably gtest - refs Add gtest 1.7.0-cxx03abi & let no suffix mean cxx11 #209)
• Do we want to maintain cxx11abi packages for all boost libraries?

[tmpsantos]

@springmeyer what if we make CXX11ABI the default and we install a newer libc when running tests on the bots so Travis can execute code with CXX11ABI like if it had a newer Linux distro?

[jfirebaugh]

what if we make CXX11ABI the default

I'd love it if we could make that the case.

a newer libc

Did you mean to say "newer libstdc++"?

Also, isn't it not just CI bots but anywhere we deploy a binary that links against libstdc++, that needs to have a version of that library that includes the cxx11abi symbols? Is this going to be an issue? This topic isn't covered by https://github.com/mapbox/cpp#should-i-install-libstdc6-instead-of-libstdc-5-dev.

[springmeyer]

@springmeyer what if we make CXX11ABI the default and we install a newer libc when running tests on the bots so Travis can execute code with CXX11ABI like if it had a newer Linux distro?

I would also like to push for this being the default. The challenge however is that it would force CI bots running on precise to change from being sudo:false to sudo:required so they also could edit the C++ header files to enable -DGLIBCXX_USE_DUAL_ABI=1 per #268 (comment). And this is not desirable because sudo:required machines boot much slower and are generally less powerful than sudo:false machines. However maybe we could try sudo:false with dist:trusty. This might work if:

• trusty packages of libstdc++ don't disable GLIBCXX_USE_DUAL_ABI (like the precise packages) and...
• travis trusty sudo:false machines get their whitelisted packages finished by the travis team - refs APT whitelist request for libstdc++-5-dev in Trusty travis-ci/apt-package-safelist#3597

Other alternatives could be:

• Package libstdc++ in mason to avoid being burned by the ubuntu-toolchain-r default of disabling GLIBCXX_USE_DUAL_ABI