some improvements

[morningstarxcdcode]

This pull request introduces enhanced debugging and error handling in the session.c file to improve the robustness and traceability of the session management logic. Key changes include adding verbose logging for better traceability, handling errors when opening files, and safely managing unknown commands.

Debugging Enhancements:

• Added verbose logging to trace function calls and key operations:
  • Logged calls to conf_cmd_file and session_do_step with relevant session data. [1] [2]
  • Logged when a configuration file does not exist or fails to open. [1] [2]

Error Handling Improvements:

• Ensured safe handling of file operations:
  • Checked if the configuration file pointer is valid before attempting to close it.
  • Added a check to handle failures when opening a configuration file, with appropriate logging and early return.
• Safely managed unknown commands in session_do_step by logging and providing a placeholder for future handling.

Code Standards:

• Defined _POSIX_C_SOURCE 200809L to ensure compatibility with POSIX features.