Discussion with Kitware about next round of work

kitware_03_09_2024_upstream_contract.md

+# Issues we definitely want fixed
+
+https://gitlab.kitware.com/cmake/cmake/-/issues/21475 multi-config install fix
+
+Notes:
+This one is clear from Kitware's, it's just a difference between invoking ninja and `cmake --build .`, which should be made to behave the same.
+
+https://gitlab.kitware.com/cmake/cmake/-/issues/24833 better find_package logs
+
+Kitware will discuss which approach is best, log rotation, finding out what is the first cmake run, or something else, and come back to us.
+
+# Work scope and specifics for
+
+https://gitlab.kitware.com/cmake/cmake/-/issues/25790
+
+Kitware will recheck estimate, might have been based on the wrong issue.
+
+
+# General discussion about windows path issues.
+
+CMake windows path length issues
+https://gitlab.kitware.com/cmake/cmake/-/issues/25639
+https://gitlab.kitware.com/cmake/cmake/-/issues/25936
+https://gitlab.kitware.com/cmake/cmake/-/issues/25797
+https://gitlab.kitware.com/cmake/cmake/-/issues/22811
+https://gitlab.kitware.com/cmake/cmake/-/issues/22435
+https://gitlab.kitware.com/cmake/cmake/-/issues/21337
+https://gitlab.kitware.com/cmake/cmake/-/issues/19675
+https://gitlab.kitware.com/cmake/cmake/-/issues/18586
+https://gitlab.kitware.com/cmake/cmake/-/issues/16485
+https://gitlab.kitware.com/cmake/cmake/-/issues/16223
+https://gitlab.kitware.com/cmake/cmake/-/issues/15859
+
+Qt one
+https://bugreports.qt.io/browse/QTBUG-117413
+
+
+# My investigation notes
+Looked a bit into the windows long path issue
+- https://gitlab.kitware.com/cmake/cmake/-/issues/25639
+    - CMake doesn't support 8.3 file paths, it expands them into long ones
+- https://gitlab.kitware.com/cmake/cmake/-/blob/v3.28.1/Source/kwsys/EncodingCXX.cxx#L233-283
+    - CMake uses a function to use UNC long-path based paths, even if Windows long paths is disabled, but it's not used in all places where paths are processed within CMake
+- https://gitlab.kitware.com/cmake/cmake/-/issues/25936
+    - CMake uses some ChangeDirectory/ CreateProcess Windows API, that seems to not work with long paths even if the tool is made long path aware, needs rechecking
+- CMake could use junctions internally like Qt Creator does, but this is a mitigation
+- Just using short file paths doesn't seem to be sufficient, due to the CreateProcess issue
+- Just fixing the CreateProcess issue is not sufficient because cl.exe is not long path aware
+- Using both short paths and a CreateProcess fix might be enough to circumvent cl.exe issue, but CreateProcess fix would be on Windows side
+- Qt also has issues due to using FetchContent, which increases the build path substantially
+- Sample qml long path
+- `C:/Users/frede/Dev/ourapp/build-ourapp-Desktop_Qt_6_5_2_MSVC2019_64bit-Debug/MediaLibrary/qml/MediaLibrary/Controls/Styles/CMakeFiles/ABMediaLibraryControlsStylesQMLplugin.dir/./ABMediaLibraryControlsStylesQMLplugin_MediaLibrary_Controls_StylesPlugin.cpp.obj`
+    - user path, creator build dir name, qml uri, `CMakeFiles`, plugin target name,` plugintargetnamePlugin.cpp.obj` file
+- Setting CMAKE_OBJECT_PATH_MAX to a lower value like 160, with MinGW prevents the generation of hashes for some reason, as opposed to leaving it at 250
+    - compiler fails to read / write the .d dep file
+    - Default generated path is
+    - `-MF CMakeFiles\chapter6-plugins.dir\748d9f7da55b8d98448fb9a66dc59300\chapter6-plugins_qmlcache_loader.cpp.obj.d`
+    - With value set to 160 it is
+    - `-MF CMakeFiles\chapter6-plugins.dir\build\Desktop_Qt_6_7_2_MinGW_64_bit-Debug\.rcc\qmlcache\chapter6-plugins_qmlcache_loader.cpp.obj.d`
+    - It's strange that the `CMakeFiles\chapter6-plugins.dir` part is not elided, and why the default path contains `build\Desktop_Qt_6_7_2_MinGW_64_bit-Debug\` in the name
+- Commented some of the findings on qt bug
+
+
+Notes:
+There are repsonse files workarounds employed by cmake for command line length limitations,
+but not in all cases. These could be improved on case by case basis.
+
+Integrating the junction idea into cmake proper ,does not seem feasible, too much magic,
+all tools and diagnostic messages would refer to junctioned paths.
+Unclear how to handle relative paths that go out of source dir reliably.
+
+Idea to improve on the long path for the qml case above would be to get rid of the
+`MediaLibrary/qml/MediaLibrary/Controls/Styles` part in the build dir
+replace the `ABMediaLibraryControlsStylesQMLplugin.dir/` part with a short hash of the dir,
+and the `ABMediaLibraryControlsStylesQMLplugin_MediaLibrary_Controls_StylesPlugin.cpp.obj`
+with a hash of the object file name. Perhaps allow customizing the object file name directly
+via a source file property.
+
+AP: Alexandru: open an issue on cmake's `qt` project bug tracker project.
+Open one task for each work item that we are requesting.