Portability: HAL for Win32 thread/atomic/sync primitives (POSIX backend)

[felixx-sp]

Confidence: high · Effort: large (>3 d)

Problem

The whole engine in bruteforce.cu uses Win32 primitives: CRITICAL_SECTION, InterlockedExchange/Add64, _beginthreadex/_stdcall, WaitForSingleObject/CreateEventA, SetThreadAffinityMask, GetTickCount64, QueryPerformanceCounter. None of this is fundamentally Windows-only — C11 <threads.h> + <stdatomic.h> + pthread_setaffinity_np cover all of it. The GUI can stay Windows-only.

Files: src/bruteforce.cu:24, 27, 1609, 1621, 1635-1639, 2564-2587, plus src/bruteforce.c if [resync issue] lands first.

Suggested fix

Step 1 (this issue): introduce

• include/os_atomic.h (Interlocked* → atomic_* wrappers)
• include/os_thread.h (thread spawn/join, mutex, event, affinity)
• include/os_time.h (high-res clock)

with Win32 + POSIX backends behind #ifdef _WIN32. Port the engine code in bruteforce.cu and bruteforce.c to use them. Leave gui.c/main.c Windows-only behind -DBUILD_GUI.

Why it matters

Unlocks a headless Linux build, opens contributions to non-Windows developers, and enables CI to run native Linux tests on free GitHub runners. Pairs with the CMake migration and CLI mode issues.