cmake: Use “coverage” preset instead of “Coverage” build type and document it #1251

1. 
   hebasto commented at 2:00 pm on March 28, 2023: member

   Using -DCMAKE_BUILD_TYPE=Coverage to configure the build for coverage analysis has a flaw as build types are not defined at the configuration stage for multi-config generators.

   This PR implements the idea suggested here.

   Please note that both added to the README.md commands, cmake --build build and ctest --test-dir build, accept the -j $(nproc) option to parallelize work.

   Drafted as it is based on #1234.

2. hebasto force-pushed on Mar 28, 2023
3. in CMakePresets.json:23 in ba602344ba outdated

   22+    {
   23+      "name": "coverage",
   24+      "displayName": "Build for coverage analysis",
   25+      "generator": "Unix Makefiles",
   26+      "cacheVariables": {
   27+        "CMAKE_C_COMPILER": "gcc",
   

   ---

   ---

   

   real-or-random commented at 9:33 pm on March 28, 2023:

   https://clang.llvm.org/docs/SourceBasedCodeCoverage.html clang supports this too, so no need to set a default here, I think.

   ---

   

   hebasto commented at 11:22 am on March 29, 2023:

   Doesn’t clang require the use of the llvm-cov tool, which is currently undocumented in the README.md?
4. 
   theuni commented at 10:09 am on April 27, 2023: contributor

   Concept ACK assuming one can stack multiple presets at once.
5. cmake: Use "coverage" preset instead of "Coverage" build type 19ead5e5e6
6. cmake, doc: Document test coverage using CMake-based build system 98bed068c6
7. hebasto force-pushed on Apr 27, 2023
8. hebasto marked this as ready for review on Apr 27, 2023
9. 
   hebasto commented at 10:37 am on April 27, 2023: member

   Rebased.
10. 
    theuni commented at 11:22 am on April 27, 2023: contributor

    After a discussion about this in-person, we’ve found drawbacks in the build type approach as well as the preset one.

    Instead, let’s just do the simple thing and hook up a new option.

11. hebasto marked this as a draft on Apr 28, 2023
12. 
    hebasto commented at 10:44 pm on April 29, 2023: member

    After a discussion about this in-person, we’ve found drawbacks in the build type approach as well as the preset one.

    Instead, let’s just do the simple thing and hook up a new option.

    Closing in favour of #1291.

13. hebasto closed this on Apr 29, 2023

    ---

14. hebasto deleted the branch on Jun 6, 2023
15. 
    hebasto commented at 1:24 am on August 11, 2025: member

    After a discussion about this in-person, we’ve found drawbacks in the build type approach as well as the preset one. Instead, let’s just do the simple thing and hook up a new option.

    Closing in favour of #1291.

    Another reincarnation of this approach is here.

    It works with both single-config and multi-config generators.

    The following are examples workflow on Ubuntu 24.04:

    • a single-config generator:

    0cmake --preset coverage -DCMAKE_GENERATOR="Ninja"
    1cmake --build --preset coverage
    2ctest --preset coverage
    

    • a multi-config generator:

    0cmake --preset coverage -DCMAKE_GENERATOR="Ninja Multi-Config"
    1cmake --build --preset coverage
    2ctest --preset coverage
    

    In the future, with CMake 3.25 or newer, we can use a single invocation:

    0cmake --workflow --preset coverage
    

Contributors
hebasto real-or-random theuni