C++

This guide covers configuring C++ projects on Semaphore. If you’re new to Semaphore we recommend reading the Guided tour first.

Table of contents:

Hello world

# .semaphore/semaphore.yml
version: v1.0
name: Hello Semaphore
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu1804
blocks:
  - name: C++ example
    task:
      jobs:
      - name: Compile and run C++ code
        commands:
          - printf "#include <iostream>\n int main() { std::cout << \"Hello world\"; return 0; }" > hello.cc
          - g++ hello.cc -o hello
          - ./hello

Supported compiler versions

Semaphore VM is 64-bit and provides the following versions of the g++ compiler:

  • g++ 4.8: found as /usr/bin/g++-4.8
  • g++ 5: found as /usr/bin/g++-5
  • g++ 6: found as /usr/bin/g++-6
  • g++ 7: found as /usr/bin/g++-7
  • g++ 8: found as /usr/bin/g++-8

The default version of the g++ compiler can be found as follows:

$ g++ --version
g++ (Ubuntu 4.8.5-4ubuntu8) 4.8.5
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Changing compiler version

The following Semaphore 2.0 project selects two different versions of g++:

version: v1.0
name: Using C++ in Semaphore 2.0
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu1804

blocks:
  - name: Change g++ version
    task:
      jobs:
      - name: Select g++ version 6
        commands:
          - g++ --version
          - sem-version cpp 6
          - g++ --version

      - name: Select g++ version 8
        commands:
          - g++ --version
          - sem-version cpp 8
          - g++ --version

Dependency management

You can use Semaphore's cache tool to store and load any files or C++ libraries that you want to reuse between jobs.

System dependencies

C++ projects might need packages like database drivers. As you have full sudo access on each Semaphore 2.0 VM, you are free to install all required packages.

A sample project

The following .semaphore/semaphore.yml file compiles and executes a C++ source file using two different versions of the g++ compiler, in parallel:

version: v1.0
name: Using C++ in Semaphore 2.0
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu1804

blocks:
  - name: Compile and run C++ code
    task:
      jobs:
      - name: Hello World!
        matrix:
          - env_var: GPP_VERSION
            values: [ "7", "8" ]
        commands:
          - checkout
          - sem-version cpp $GPP_VERSION
          - g++ hw.cpp -o hw
          - ./hw

The contents of the hw.cpp file are as follows:

#include <iostream>

int main()
{
    std::cout << "Hello, World!\n";
    return 0;
}

See Also

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