Linux 16.04LTS下QT+CUDA+OpenGL开发编译报错求助

Hey Andy, let's break down and fix these two frustrating issues you're hitting with your Qt+CUDA+OpenGL application on Ubuntu 16.04 LTS. I've dealt with both of these before, so here's what you can try:

This error usually boils down to missing dependencies for the xcb plugin or incorrect environment variables pointing Qt to the right plugin directory. Here's how to debug and fix it:

• Enable plugin debug logging to pinpoint the issue
  Run your application with the QT_DEBUG_PLUGINS environment variable set to 1 to get detailed logs about why the xcb plugin is failing to load:

  QT_DEBUG_PLUGINS=1 ./your_application_name
  

  Look for lines like "Cannot load library..." or "Missing symbol..."—this will tell you exactly what's missing.

• Install missing xcb dependencies
  Ubuntu 16.04 often lacks some optional xcb libraries that Qt's xcb plugin relies on. Run this command to install common missing packages:

  sudo apt-get update && sudo apt-get install libxcb-xinerama0 libxcb-randr0 libxcb-util0 libxcb-cursor0 libxcb-xkb1
  

  If the debug logs show a specific missing library, install that package specifically (use apt-cache search <library-name> to find the package).

• Ensure Qt's platform plugin path is correctly set
  If you're using a custom Qt installation (not the system Qt), make sure the QT_QPA_PLATFORM_PLUGIN_PATH environment variable points to the platforms plugin directory. For example, if Qt is installed at /opt/Qt/5.9/gcc_64:

  export QT_QPA_PLATFORM_PLUGIN_PATH=/opt/Qt/5.9/gcc_64/plugins/platforms
  ./your_application_name
  

  If you're using Qt Creator, check the "Run Environment" tab in your project settings to ensure this variable is set correctly.

• Fix library path conflicts with CUDA
  Sometimes CUDA's library path can override Qt's, causing Qt to load the wrong versions of libraries. Adjust your LD_LIBRARY_PATH to prioritize Qt's libraries first:

  export LD_LIBRARY_PATH=/opt/Qt/5.9/gcc_64/lib:$LD_LIBRARY_PATH
  ./your_application_name
  

This is a classic C++ linking issue related to virtual functions in your MainWindow class. Here's what to check:

• Ensure all pure virtual functions are implemented
  If your MainWindow class inherits from an abstract class (or has its own pure virtual functions marked with = 0), every single one of those functions must have an implementation in your .cpp file. For example, if your header has:

  class MainWindow : public QMainWindow {
      Q_OBJECT
  public:
      virtual void customVirtualFunc() = 0; // Pure virtual function
  };
  

  You must have this in mainwindow.cpp:

  void MainWindow::customVirtualFunc() {
      // Implementation here
  }
  

  Missing implementations will cause the linker to fail to generate the vtable for MainWindow.

• Verify your build system includes all source files

  • If using qmake: Check your .pro file to make sure mainwindow.cpp is listed in the SOURCES section:

    SOURCES += main.cpp \
               mainwindow.cpp
    

  • If using CMake: Ensure mainwindow.cpp is added to your add_executable or cuda_add_executable command:

    add_executable(your_app main.cpp mainwindow.cpp)
    

  Forgetting to include the source file means the linker never sees the implementation of MainWindow's functions.

• Check CUDA and Qt mixed compilation settings
  Since you're combining Qt with CUDA, make sure your build system is handling C++ and CUDA files correctly:

  • For qmake: Use the CUDA_SOURCES variable for your .cu files, and ensure Qt's MOC tool is processing your MainWindow header correctly (the Q_OBJECT macro requires MOC to generate code, which qmake usually handles automatically, but double-check).
  • For CMake: Use find_package(Qt5 REQUIRED COMPONENTS ...) and target_link_libraries to link Qt's libraries, and use cuda_add_executable if your app includes CUDA code. Ensure there's no conflict between CUDA's compiler flags and Qt's.

• Check for linker order issues
  Make sure Qt's libraries are linked after your source files in your build configuration. For example, in CMake, target_link_libraries(your_app Qt5::Widgets) should come after the source files in add_executable. Incorrect order can lead to missing symbol errors.

Give these steps a try—start with the debug logs for the xcb issue, since that's often a quick fix, then tackle the vtable error. Let me know if you need more details on any of these steps!

内容的提问来源于stack exchange，提问作者Andy