CMake Cleanup Part 2

[stonier]

• make use of target_include_directories instead of include_directories ⇨ [infra] wipe out global include_directories #482
• collapse library targets in backend ⇨ [infra] backend library and exported targets #507
• LCM still needed in SearchForStuff.cmake? No ⇨ [infra] review and update finding of 3rd party packages #473
• review and consider dropping SearchForStuff.cmake ⇨ [infra] review and update finding of 3rd party packages #473
• review and drop unused parts of Utils.cmake (drop entirely?) ⇨ [infra] review and update finding of 3rd party packages #473, [infra] wipe out global include_directories #482
• review the CFlags maze Cleanup the CXX_FLAGS. #565
• review and simplify, drop unused parts in the root CMakeLists.txt ⇨ [infra] wipe out global include_directories #482

[apojomovsky]

Hi @stonier, I'm currently looking to finish this issue so that we can finally close it.
May I ask you a brief explanation on what's expected for the remaining item "Review the CFlags maze"?
Thanks in advance!

[stonier]

I simply hadn't parsed it yet. As with other parts of the CMake it is likely way overkill for our needs. Keeping it simple will foster easier maintenance going forward.

[clalancette]

Going through the cmake stuff in Delphyne, I see the following that tries to add compiler flags:

• CMakeLists.txt at the top
  • Includes cmake/Utils.cmake
    • Utils.cmake actually defines the filter_valid_compiler_warnings macro that the top-level CMakeLists.txt uses to see if the compiler supports certain warning flags
  • Includes cmake/HostCFlags.cmake
    • HostCFlags includes FindSSE.cmake
    • If FindSSE.cmake find SSE, then HostCFlags adds the SSE flags to CMAKE_C_FLAGS_ALL.
  • Includes cmake/DefaultCFlags.cmake
    • This adds in a number of flags, depending on the CMAKE_BUILD_TYPE (things like debugging, profiling, etc).
    • This also currently adds in -rdynamic to the link flags, though that is no longer needed.
  • Attempts to add flags on its own using the filter_valid_compiler_warnings macro from Utils.
• Looking through the rest of the CMakeLists.txt in the delphyne repository, nothing else actually adds flags, so the above is the full list of what touches flags.

With that in mind, I'm not sure exactly what we could simplify. We could just assume that we are always on g++ on an amd64 machine, which would simplify some of this machinery, but it has been useful at times in the past to compile with clang. As far as -rdynamic goes, we no longer need that, so I'll open a PR removing those flags. Otherwise, I'm not sure that we can change too much here, other than moving flags from the top-level CMakeLists.txt so that they are hidden in one of the cmake/* files. @stonier , thoughts?

[clalancette]

Since all of the items here are now checked off, I'm going to close this out. Feel free to reopen (or open a new issue) if there is anything missing.