GetProcessGroupAffinity requires the memory for [out] PUSHORT GroupArray to be overaligned. Is this (bug?) documented anywhere? Is this even a bug? The only mention I could find is here https://fossies.org/linux/fio/os/windows/cpu-affinity.c at line 236.

Reproduction:

#include <windows.h>
#include <iostream>

int main()
{
    USHORT GroupCount = 1;
    alignas(4) USHORT GroupArray[2];

    auto status = GetProcessGroupAffinity(GetCurrentProcess(), &GroupCount, GroupArray);
    auto a = GetLastError();
    std::cout << a << ' ' << status << 'n';
    
    status = GetProcessGroupAffinity(GetCurrentProcess(), &GroupCount, GroupArray + 1);
    a = GetLastError();
    std::cout << a << ' ' << status << 'n';
}

g++ a.cpp -static && ./a prints

998 0
998 1

If anything, let this post serve as documentation for people searching for this issue (I intentionally worded the title this way to facilitate this, please don’t change it)