Declare mockturtle as a SYSTEM library in CMake

[marcelwa]

Libraries declared as SYSTEM do not propagate compiler warnings to top-level projects. Thereby, when using mockturtle as a library while having a stricter compiler warnings setup, this suppresses warnings originating in mockturtle. Since the test cases now link PUBLICly, you are still able to see all warnings as before while working on mockturtle. The changes only affect people including it.

For more information see, e.g., https://foonathan.net/2018/10/cmake-warnings/

A nice compiler warnings setup can be found in Jason Turner's CPP Starter Project here: https://github.com/lefticus/cpp_starter_project/blob/master/cmake/CompilerWarnings.cmake

[codecov-io]

Codecov Report

Merging #437 (7b1c12f) into master (7d0f355) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #437      +/-   ##
==========================================
- Coverage   79.74%   79.72%   -0.03%     
==========================================
  Files         117      117              
  Lines       12720    12720              
==========================================
- Hits        10144    10141       -3     
- Misses       2576     2579       +3     

Impacted Files	Coverage Δ
...nclude/mockturtle/algorithms/dsd_decomposition.hpp	87.14% <0.00%> (-4.29%)	⬇️

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[coveralls]

Pull Request Test Coverage Report for Build 726086384

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 80.086%

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Totals
Change from base Build 725561612:	0.0%
Covered Lines:	10661
Relevant Lines:	13312

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💛 - Coveralls

[hriener]

I am wondering what prevents you from declaring mockturtle as a SYSTEM library on your side, e.g., as in #432. Do you directly include the CMakeLists.txt of mockturtle in your build process?

[marcelwa]

I am by no means an expert in CMake, so I just used add_subdirectory(mockturtle). Issue #432 refers to autotools and does not really help me, unfortunately. If you can point me towards a client-side solution, I'd be more than happy to give it a try.

[hriener]

Instead of adding the subdirectory, you could just add your own target for mockturtle and declare it as SYSTEM.

However, your request sounds reasonable. I would suggest adding PUBLIC to mockturtle's examples and experiments too because they are often used as drivers during development.

[marcelwa]

If I'm not mistaken, they link PUBLICly already.

Examples:

mockturtle/examples/CMakeLists.txt

Line 6 in 7d0f355

target_link_libraries(${basename} PUBLIC mockturtle)

Experiments:

mockturtle/experiments/CMakeLists.txt

Line 30 in 7d0f355

target_link_libraries(${basename} PUBLIC experiments mockturtle)

[hriener]

Perfect! Thank you.