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🚀 Getting started with CMake RE for C++
00-getting-started

In this getting started guide we will setup your machine to perform local CMake containerized hermetic and cached builds.

  1. Install cmake-re
# Linux & MacOS:
/bin/bash -c \
 "$(curl -fsSL https://raw.githubusercontent.com/tipi-build/cli/master/install/install_for_macos_linux.sh)"
# Windows 10 / 11 in Powershell
[Net.ServicePointManager]::SecurityProtocol = "Tls, Tls11, Tls12, Ssl3"
. { `
  iwr -useb https://raw.githubusercontent.com/tipi-build/cli/master/install/install_for_windows.ps1 `
} | iex
Prerequisites for Hermetic Builds

For local containerized and hermetic build you need to install docker on your system. If you can't install it, you can use the tipi.build cloud instead with --remote. You can also launch non-hermetic builds with --host builds and still benefit from local caching.

➡ Docker Engine Installation Guide

❗️Docker Engine 27.2.0 or newer required: Check your installed version with docker version

  1. Download our get-started example CMakeLists.txt and a CMake RE environment decription ( CMAKE_TOOLCHAIN_FILE ) :
git clone https://github.com/tipi-build/get-started.git

The get-started example presents a CMake Project depending on the fmtlib that will be cached by CMake RE FetchContent support, making FetchContent a full fledged package manager ( Read more about our Compatible and Enhanced FetchContent ).

  1. Get Cached, Reproducible Hermetic CMake builds :
cmake-re -S . -B build/ -DCMAKE_TOOLCHAIN_FILE=environments/linux.cmake

This will launch the container on your machine and execute the build inside it. Build artifacts will be cached.

Content of a CMake RE project

A CMake RE project is a plain CMake project with the addition of environment descriptions to guarantee the build reproducibility and hermeticity.

This allows CMake builds to always get a well-defined environment for reproducible builds, making build caching and remoting possible.

Environment Descriptions are made of :

    • A CMAKE_TOOLCHAIN_FILE, e.g. environment/linux.cmake
    • An accompanying .pkr.js and Dockerfile, e.g. environments/linux.pkr.js/, environments/linux.pkr.js/linux.Dockerfile

Learn more about Environments.

Environments are not limited to docker containers, Virtual Machine images are also usable.

├── CMakeLists.txt
├── environments
│   ├── linux.cmake
│   └── linux.pkr.js
│       ├── linux.Dockerfile
│       └── linux.pkr.js
└── test
    └── main.cpp

CMakeLists.txt

cmake_minimum_required(VERSION 3.27.6)

project(get-started)
enable_testing()

# Install fmt
Include(FetchContent)
set(FMT_TEST OFF CACHE BOOL "" FORCE)
FetchContent_Declare(fmt
  GIT_REPOSITORY https://github.com/fmtlib/fmt.git
  GIT_TAG        9.0.0
  OVERRIDE_FIND_PACKAGE
)
FetchContent_MakeAvailable(fmt)
find_package(fmt REQUIRED)

# Add a test executable
add_executable(main test/main.cpp)
target_link_libraries(main PRIVATE fmt::fmt)

add_test(NAME main COMMAND ${CMAKE_CROSSCOMPILING_EMULATOR} $<TARGET_FILE:main> )

test/main.cpp

#include <fmt/core.h>

int main() {
    fmt::print("Good Morning Caching & Hermetic Builds :-) \n"); 
    return 0;
}

CMAKE_TOOLCHAIN_FILE= environments/linux.cmake

if(DEFINED POLLY_LINUX_CMAKE_)
  return()
else()
  set(POLLY_LINUX_CMAKE_ 1)
endif()

if (NOT CMAKE_HOST_SYSTEM_NAME STREQUAL "Linux") 
  message(FATAL_ERROR "Incompatible System Toolchain, you are running the build on '${CMAKE_HOST_SYSTEM_NAME}' and this toolchain is made for 'Linux'.")
endif()

include("${CMAKE_CURRENT_LIST_DIR}/compiler/clang.cmake")
include("${CMAKE_CURRENT_LIST_DIR}/flags/cxx17.cmake")

environments/linux.pkr.js/linux.pkr.js

{
  "variables": { },
  "builders": [
    {
      "type": "docker",
      "image": "tipibuild/tipi-ubuntu:{{tipi_cli_version}}", // The Docker to use
      "commit": true                                         // or update when Dockerfile present
    }
  ],
  "post-processors": [
    { 
      "type": "docker-tag",
      "repository": "linux",
      "tag": "latest"
    }
  ],
  "_tipi_version":"{{tipi_version_hash}}"
}

Aside of the CMAKE_TOOLCHAIN_FILE the pkr.js folder specifies the environment that will be used for the build. This is a packer docker builder configuration, different to plain packer cmake-re will build the Docker image if it cannot be found on a registry or if any change was made to the linux.Dockerfile.

In this specific case we just take the default tipi.build provided linux docker environment with its installed clang toolchain.

More details in Environments

Hint: for a "compile & test as you type" experience try adding --monitor and --run-test all to the command line. cmake-re will then trigger a (re)build and test execution each time a file changes.