How to automatically download C++ dependencies in a cross platform way + CMake?

Question

Basically I want to achieve this workflow:

1. Checkout from repository on windows system (or any platform for that matter).

2. Run some tool that gets dependencies, both includes and libs and puts them in their proper place (like in "\Program Files\Microsoft Visual Studio 10.0\VC\Lib and \Includes" on windows)

3. Run CMake (creates MSVS projects on win)

4. Open up MSVS project and compile it.

And i would like to have this workflow on most platforms.

I dont want to have to download dependencies manually

How to do this without storing dependencies in repository? What is the best way to achieve this?

Answer 1

In CMake you can use file(DOWNLOAD URL PATH) to download a file, combine this with custom commands to download and unpack:

set(MY_URL "http://...") set(MY_DOWNLOAD_PATH "path/to/download/to") set(MY_EXTRACTED_FILE "path/to/extracted/file")  if (NOT EXISTS "${MY_DOWNLOAD_PATH}")     file(DOWNLOAD "${MY_URL}" "${MY_DOWNLOAD_PATH}") endif()  add_custom_command(     OUTPUT "${MY_EXTRACTED_FILE}"     COMMAND command to unpack     DEPENDS "${MY_DOWNLOAD_PATH}") 

Your target should depend on the output from the custom command, then when you run CMake the file will be downloaded, and when you build, extracted and used.

This could all be wrapped up in a macro to make it easier to use.

You could also look at using the CMake module ExternalProject which may do what you want.

Answer 2

From cmake 3.11 on there is a new feature: FetchContent

You can use it to get your dependencies during configuration, e.g. get the great cmake-scripts.

include(FetchContent)  FetchContent_Declare(   cmake_scripts   URL https://github.com/StableCoder/cmake-scripts/archive/master.zip) FetchContent_Populate(cmake_scripts) message(STATUS "cmake_scripts is available in " ${cmake_scripts_SOURCE_DIR}) 

I prefer fetching the ziped sources instead of directly checking out. But FetchContent also allows to define a git repository.