Details
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User Story
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Resolution: Out of scope
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Not Evaluated
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None
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6.8.2
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None
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macOS
Description
It seems that the starship operator cannot be applied to const QString objects when compiling on MacOS.
I have a small project that I recently moved from C+17 to C+20, introducing where suitable the starship operator (<=>).
I also ensured that CMakeLists.txt contains both the following lines:
set(CMAKE_CXX_STANDARD 20) set(CMAKE_CXX_STANDARD_REQUIRED ON)
While the project compiles smoothliy on Linux (gcc 13) and Windows (both MinGW and MSVC), the XCode compiler stops early and shows the following error:
[ 28%] Building CXX object CMakeFiles/MyApp.dir/MyApp_autogen/mocs_compilation.cpp.o /Applications/Xcode-16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -DQT_CORE_LIB -DQT_GUI_LIB -DQT_NO_DEBUG -DQT_WIDGETS_LIB -I/Users/distiller/project/build -I/Users/distiller/project -I/Users/distiller/project/build/MyApp_autogen/include -isystem /opt/homebrew/opt/qt/lib/QtCore.framework/Headers -iframework /opt/homebrew/opt/qt/lib -isystem /opt/homebrew/opt/qt/share/qt/mkspecs/macx-clang -isystem /opt/homebrew/opt/qt/include -isystem /opt/homebrew/opt/qt/lib/QtGui.framework/Headers -isystem /opt/homebrew/include -isystem /opt/homebrew/opt/qt/lib/QtWidgets.framework/Headers -std=gnu++20 -arch arm64 -isysroot /Applications/Xcode-16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -mmacosx-version-min=14.6 -MD -MT CMakeFiles/MyApp.dir/MyApp_autogen/mocs_compilation.cpp.o -MF CMakeFiles/MyApp.dir/MyApp_autogen/mocs_compilation.cpp.o.d -o CMakeFiles/MyApp.dir/MyApp_autogen/mocs_compilation.cpp.o -c /Users/distiller/project/build/MyApp_autogen/mocs_compilation.cpp In file included from /Users/distiller/project/build/MyApp_autogen/mocs_compilation.cpp:2: In file included from /Users/distiller/project/build/MyApp_autogen/EWIEGA46WW/moc_categoriesmodel.cpp:9: In file included from /Users/distiller/project/build/MyApp_autogen/EWIEGA46WW/../../../categoriesmodel.hpp:26: /Users/distiller/project/build/MyApp_autogen/EWIEGA46WW/../../../category.hpp:99:42: error: invalid operands to binary expression ('const QString' and 'const QString') 99 | return (lhs.getFullDescription() <=> rhs.getFullDescription()); | ~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~ 1 error generated. make[2]: *** [CMakeFiles/MyApp.dir/MyApp_autogen/mocs_compilation.cpp.o] Error 1 make[1]: *** [CMakeFiles/MyApp.dir/all] Error 2 make: *** [all] Error 2 Exited with code exit status 2
I split the compile command on many lines to improve readability and I would like to pinpoint some important things:
- the -std=gnu++20 is present;
- the function getFullDescription() returns a QString const reference since its signature is QString const &getFullDescription() const;.
I compile for both Linux and Windows on a machine owned by myself, while I rely on an external service (CircleCI) to compile for MacOS.
I tried downgrading to Xcode-16.1 without any change.
What I am asking is to understand if this is a bug of the compiler or something to fix in the Qt library when compiled for MacOS.