Worked on the openssl/openssl repository to stabilize 64-bit Windows MinGW builds by resolving pointer type errors in atomic store operations. Addressed compatibility issues in crypto/threads_win.c by implementing explicit casts for InterlockedExchange and InterlockedExchange64 calls, ensuring correct handling of LONG and LONG64 volatile pointers. This fix enabled successful 64-bit Windows builds and improved the reliability of cryptographic primitives, particularly for FIPS self-test atomic state access. The work involved C programming, Windows API, and multithreading, and was merged through a collaborative code review process. The contribution focused on cross-compiler debugging and hardening atomic operations for robust Windows support.