Travis

Build a C++ Project

For Language versions and other build-environment specific information visit our reference pages:

This guide covers build environment and configuration topics specific to C++ projects. Please make sure to read our Onboarding and General Build configuration guides first.

CI Environment for C++ Projects #

Travis CI VMs are 64-bit and provide versions of:

  • gcc
  • clang
  • core GNU build toolchain (autotools, make), cmake, scons

C++ projects on Travis CI assume you use Autotools and Make by default.

For precise versions on the VM, please consult “Build system information” in the build log.

Dependency Management #

Because there is no dominant convention in the community about dependency management, Travis CI skips dependency installation for C++ projects.

If you need to install dependencies before your tests can run, override the install: key in your .travis.yml:

install: make get-deps

See build configuration guide to learn more.

Test against Compilers #

You can test projects against either GCC or Clang, or both. To do so, specify the compiler to use using the compiler: key in .travis.yml. For example, to build with Clang:

compiler: clang

or both GCC and Clang:

compiler:
  - clang
  - gcc

Testing against two compilers will create (at least) 2 rows in your build matrix. For each row, the Travis CI C++ builder will export the CXX and CXX_FOR_BUILD env variables to point to either g++ or clang++, and correspondingly export the CC and CC_FOR_BUILD env variables to point to either gcc or clang.

Examples #

OpenMP Projects #

OpenMP projects should set the environment variable OMP_NUM_THREADS to a reasonably small value (say, 4). OpenMP detects the cores on the hosting hardware, rather than the VM on which your tests run.

MPI Projects #

The default environment variables $CC and $CXX are known to interfere with MPI projects. In this case, we recommend unsetting it:

before_install:
  - test -n $CC  && unset CC
  - test -n $CXX && unset CXX
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