Worked on the google/mozc repository to enhance the robustness of Linux username retrieval by addressing a portability issue in system programming. Implemented a defensive fallback mechanism in C++ that provides a default buffer size when sysconf(_SC_GETPW_R_SIZE_MAX) is undefined or returns -1, ensuring stable getpw-based username lookups across diverse Linux environments. This cross-platform development effort focused on error handling to reduce the risk of undefined behavior caused by varying libpwdb implementations. The solution improved the reliability of user name resolution within Mozc workflows, contributing to more consistent application behavior and maintainability across different system configurations.