Travis CI with Clang 3.4 and C++11

问题:

Is it possible to get Travis CI working with Clang that is capable of C++11? (I want Clang, not GCC, I already have GCC 4.8 working in Travis CI.) It appears that the version that is there pre-installed is not C++11 capable. All my attempts at installing any newer version end up failing because of this:

In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/move.h:57:   
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:269:39: error:
use of undeclared identifier '__float128'
struct __is_floating_point_helper<__float128>

I have seen the -D__STRICT_ANSI__ trick but that clashes with other things for me.

Is it possible to get it working? See also my .travis.yml.

回答1:

Here is a part of my .travis.yml files (mostly taken from this file).

language: cpp

compiler:
  - clang
  - gcc

before_install:
  # g++4.8.1
  - if [ "$CXX" == "g++" ]; then sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test; fi

  # clang 3.4
  - if [ "$CXX" == "clang++" ]; then sudo add-apt-repository -y ppa:h-rayflood/llvm; fi

  - sudo apt-get update -qq

install:
  # g++4.8.1
  - if [ "$CXX" = "g++" ]; then sudo apt-get install -qq g++-4.8; fi
  - if [ "$CXX" = "g++" ]; then export CXX="g++-4.8"; fi

  # clang 3.4
  - if [ "$CXX" == "clang++" ]; then sudo apt-get install --allow-unauthenticated -qq clang-3.4; fi
  - if [ "$CXX" == "clang++" ]; then export CXX="clang++-3.4"; fi

script: 
  - $CXX --version

EDIT because it can be very useful to add libc++ for travis. Up to my knowledge, there is no Linux package for libc++, so one has to compile it "by hand". Do not forget -stdlib=libc++ in CXXFLAGS while compiling with clang.

install:
  # clang 3.4
  - if [ "$CXX" == "clang++" ]; then sudo apt-get install --allow-unauthenticated -qq clang-3.4; fi
  - if [ "$CXX" == "clang++" ]; then export CXXFLAGS="-std=c++0x -stdlib=libc++"; fi
  - if [ "$CXX" == "clang++" ]; then svn co --quiet http://llvm.org/svn/llvm-project/libcxx/trunk libcxx; fi

  - if [ "$CXX" == "clang++" ]; then cd libcxx/lib && bash buildit; fi
  - if [ "$CXX" == "clang++" ]; then sudo cp ./libc++.so.1.0 /usr/lib/; fi
  - if [ "$CXX" == "clang++" ]; then sudo mkdir /usr/include/c++/v1; fi
  - if [ "$CXX" == "clang++" ]; then cd .. && sudo cp -r include/* /usr/include/c++/v1/; fi
  - if [ "$CXX" == "clang++" ]; then cd /usr/lib && sudo ln -sf libc++.so.1.0 libc++.so; fi
  - if [ "$CXX" == "clang++" ]; then sudo ln -sf libc++.so.1.0 libc++.so.1 && cd $cwd; fi

  - if [ "$CXX" == "clang++" ]; then export CXX="clang++-3.4"; fi

回答2:

There is now a better way to do this.

sudo: false
dist: trusty
language: cpp
os:
  - linux
compiler:
  - gcc
  - clang
install:
# /usr/bin/gcc is 4.6 always, but gcc-X.Y is available.
- if [[ $CXX = g++ ]]; then export CXX="g++-4.9" CC="gcc-4.9"; fi
# /usr/bin/clang has a conflict with gcc, so use clang-X.Y.
- if [[ $CXX = clang++ ]]; then export CXX="clang++-3.5" CC="clang-3.5"; fi
addons:
  apt:
    sources:
    - ubuntu-toolchain-r-test
    - llvm-toolchain-precise-3.5 # not sure why we needed this
  packages:
    - gcc-4.9
    - g++-4.9
    - clang-3.5

(The explicit sudo: false will let it build in Docker (for speed) even if you have a pre-docker repo, according to Travis support.)

Thanks to solarce at Travis support for noticing my error and fixing the docs.

• http://docs.travis-ci.com/user/apt/
• http://genbattle.bitbucket.org/blog/2016/01/17/c++-travis-ci/
• https://github.com/open-source-parsers/jsoncpp/blob/master/.travis.yml (for up-to-date example)

回答3:

It appears that the clang developers fixed this when you build in -std=gnu++11 mode.

Are you able to build with that flag instead of __STRICT_ANSI__?

• http://llvm.org/bugs/show_bug.cgi?id=13530
• http://llvm.org/viewvc/llvm-project?view=revision&revision=184476