C++#

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

Hello world#

# .semaphore/semaphore.yml
version: v1.0
name: Hello Semaphore
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2004
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:

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

$ g++ --version
g++ (Ubuntu 9.4.0-1ubuntu1~20.04.2) 9.4.0
Copyright (C) 2019 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: ubuntu2004

blocks:
  - name: Change g++ version
    task:
      jobs:
      - name: Select g++ version 9
        commands:
          - g++ --version
          - sem-version cpp 9
          - g++ --version

      - name: Select g++ version 10
        commands:
          - g++ --version
          - sem-version cpp 10
          - 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. You have full sudo access on each Semaphore 2.0 VM, so you can 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: ubuntu2004

blocks:
  - name: Compile and run C++ code
    task:
      jobs:
      - name: Hello World!
        matrix:
          - env_var: GPP_VERSION
            values: [ "9", "10" ]
        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#