javinovo / conan-cmake-hello

Creating and consuming Conan packages using CMake

This repository shows how to create a basic Conan example package and how to build code consuming it using CMake.

Install Conan in your system:

pip3 install conan

Creating the package

We will use Conan to create a package with testing. Conan assumes by default that the package will be an external project checking out the source from git. Here, we want to have the package information along the source code. For simplicity, we will re-use the source code provided by Conan as example.

Steps

Create the package folder:

mkdir package && cd package

Create the package recipe (conanfile.py), the package testing folder(test_package) and the source folder (src):

conan new Hello/0.1 -t -s

Build the package for the demo user and testing channel, testing using test_package and add it to the local repository:

conan create . demo/testing

Inspect the package in the local repository:

conan info Hello/0.1@demo/testing

Consuming the package

To consume a package we must create a file to declare the dependency and invoke the Conan CLI to satisfy it right before building with CMake.

Steps

Create the consumer folder:

mkdir consumer && cd consumer

Create main.cpp containing:

#include <iostream>
#include "hello.h"

int main() {
    hello();
}

Create conanfile.txt declaring a dependency on the package and that a CMake support file must be generated:

[requires]
Hello/0.1@demo/testing

[generators]
cmake

Create CMakeLists.txt including the conanbuildinfo.cmake that will be generated by Conan and invoking the setup conan_basic_setup function declared in that file:

cmake_minimum_required(VERSION 3.10)

project(hello-consumer CXX)

# Setup Conan packages ('conan install' must be run first)
include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()

add_executable(main main.cpp)
target_link_libraries(main ${CONAN_LIBS})

Create the build folder

mkdir build && cd build

Install packages and generate the required conanbuildinfo.cmake CMake support file. The path points to the location of the conanfile.txt file:

conan install ..

Configure and generate CMake build:

cmake -DCMAKE_BUILD_TYPE=Release ..

Build:

cmake --build .

Run:

bin/main

Consuming the package through CMake

This is a variation of the previous, automatically installing the packages from CMake to avoid having to use the CLI.

Steps

Create the consumer-cmake folder:

mkdir consumer-cmake && cd consumer-cmake

Create main.cpp containing:

#include <iostream>
#include "hello.h"

int main() {
    hello();
}

Create CMakeLists.txt which will download a conan.cmake CMake wrapper file which provides the conan_cmake_run function to install package dependencies from whithin CMake instead of having to invoke the CLI:

cmake_minimum_required(VERSION 3.10)

project(hello-consumer-cmake CXX)

# Download automatically, you can also just copy the conan.cmake file
if(NOT EXISTS "${CMAKE_BINARY_DIR}/conan.cmake")
   message(STATUS "Downloading conan.cmake from https://github.com/ conan-io/cmake-conan")
   file(DOWNLOAD "https://raw.githubusercontent.com/conan-io/cmake-conan/   master/conan.cmake"
                  "${CMAKE_BINARY_DIR}/conan.cmake")
endif()
include(${CMAKE_BINARY_DIR}/conan.cmake)

# Install required packages
conan_cmake_run(REQUIRES Hello/0.1@demo/testing
                BASIC_SETUP)

add_executable(main main.cpp)
target_link_libraries(main ${CONAN_LIBS})

Configure and generate CMake build:

mkdir build && cd build
cmake -DCMAKE_BUILD_TYPE=Release ..

Build:

cmake --build .

Run:

bin/main