new QFile("some.txt") fails with "device not open" when windows screen locked

  • 9 months ago
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The error "device not open" when trying to create a QFile in Qt might indicate that there is an issue with file access permissions, file locks, or other file-related operations. If this error occurs when the Windows screen is locked, it's possible that the operating system is restricting file access during that time. Here are some steps you can take to troubleshoot the issue:

  1. Check File Path:
    Ensure that the file path you're using is correct. It's possible that an incorrect path could lead to this error.

  2. File Locks:
    Check if the file is locked by another process or application. If the file is open or locked by another program, you might not be able to access it.

  3. File Permissions:
    Verify that the user account your application is running under has the necessary permissions to access the file. Permissions issues can lead to "device not open" errors.

  4. File Handle Leak:
    Make sure you're properly closing any previously opened file handles before attempting to create a new QFile. Leftover file handles from previous operations could cause this issue.

  5. Check Screen Lock Settings:
    Confirm that the issue occurs consistently when the screen is locked. If the issue only happens during specific conditions (such as screen locking), investigate whether any power-saving or security settings are affecting file access.

  6. Use Absolute Paths:
    Instead of relying on relative paths, consider using absolute paths to ensure that you're accessing the correct file location.

  7. Check File System Type:
    Verify that the file system type (NTFS, FAT32, etc.) on the drive where the file resides supports the required file operations.

  8. Run as Administrator:
    Try running your application with administrator privileges to rule out any permission-related issues.

  9. Windows Sleep Mode:
    If the system goes into sleep mode, certain file operations might be restricted. Check if the issue persists after waking the system from sleep mode.

  10. Antivirus or Security Software:
    Some antivirus or security software might interfere with file access. Temporarily disable such software and see if the issue persists.

  11. Qt and Windows Versions:
    Ensure you're using a compatible version of Qt and that there are no known issues related to the Qt version you're using on your Windows version.

  12. Debugging and Logs:
    Add debug statements to your code to log relevant information about the error. This can help you gather more information about what's causing the issue.

If none of these steps resolve the issue, it might be helpful to provide more context about your code, the environment, and the specific conditions under which the error occurs. This can aid in diagnosing the problem more accurately.