Zisa
Conan

Conan is a wonderful tool to download and install compiled libraries to a local folder on your computer. In addition it generates the necesary information to link against these local versions.

It can be installed either using the package manager or 

$ pip install --user conan

(or pip3 depending on your Linux distribution).

Quick Conan Primer

Conan Profiles

In order to obtain ABI compatible libraries, Conan must be told which compiler, compiler version and which standard library should be used. My initial faulty assumption was it would just deduce everything from the environment variable CC. Instead Conan has a concept of "profiles" which are textfiles containing all the relevant information.

One easy way setup a custom profile would be to run 

$ conan profile show default

and see what can/needs to be modified. Then create a new profile PROFILE in the folder ~/.conan/profiles. Use this profile by 

$ conan install CONANFILE --profile PROFILE

where CONANFILE is typically ../conanfile.txt and PROFILE is the name of the file you created in ~/.conan/profiles, e.g., default if you want to redundantly specify the default profile.

C++11 Standard Library

Modern C++ links to a C++11 compatible version of the standard library. Conan must be told to use the modern library, either by modifying a profile (possibly the default) or by adding 

$ conan CONANFILE -s compiler.libcxx=libstdc++11

Combining CMake and Conan

Conan and CMake work very nicely together. There are several ways of combining the two. The rationale is to avoid a strong coupling of the two. Therefore, we strive for a CMakeLists.txt which does not contain Conan specific instructions. After all Conan is just a way of obtaining libraries and not the way. In particular, if all dependencies are installed in standard locations (meaning CMake can find them), then Conan should not be needed.

The two generators we use are

  • cmake_find_package which automatically generates FindXYZ.cmake.
  • cmake_paths which generates a file with the CMake variables required to find the generated FindXYZ.cmake modules.

Therefore, if we were to include(conan_paths.cmake), CMake would pickup the Conan generated find modules. Fortunately, there's an interesting trick to avoid literally including the file in CMakeLists.txt. Namely, CMake has a command line argument -DCMAKE_PROJECT_${PROJECT}_INCLUDE which can be used to include a file, e.g., conan_paths.cmake.