GeezerVison

Oh, I read WaitForSingleObject documentation of 2006 for Windows CE 3.0:
https://docs.microsoft.com/en-us/previous-versions/ms915517(v=msdn.10)

The time-out value needs to be a positive number between 0 and 0x7FFFFFFF. The maximum time-out value not equal to infinity is 0x7FFFFFFF. The infinite time-out value is 0xFFFFFFFF. Any time-out value between 0x7FFFFFFF and 0xFFFFFFFF—that is, values from 0xF0000000 through 0xFFFFFFFE—is equivalent to 0x7FFFFFFF. If you need a bigger time-out value than the maximum of 0x7FFFFFFF, use the value for infinity (0xFFFFFFFF).

Maybe this is different on Windows 10 and my change in the main branch is not correct.

In ReactOS, WaitForSingleObject() calls WaitForSingleObjectEx() which converts "DWORD dwMilliseconds" to "LARGE_INTEGER Time" with BaseFormatTimeOut()

 PLARGE_INTEGER
 WINAPI
 BaseFormatTimeOut(OUT PLARGE_INTEGER Timeout,
                   IN DWORD dwMilliseconds)
 {
     /* Check if this is an infinite wait, which means no timeout argument */
     if (dwMilliseconds == INFINITE) return NULL;
 
     /* Otherwise, convert the time to NT Format */
     Timeout->QuadPart = dwMilliseconds * -10000LL;
     return Timeout;
 }

Then WaitForSingleObjectEx() calls NtWaitForSingleObject() with the "LARGE_INTEGER Time".

So I don't see any special case for values in the [0x80000000; 0xFFFFFFFE] range. Only INFINITE is special. In ReactOS, INFINITE is defined as:

#define INFINITE MAXULONG

I understand that INFINITE is equal to 0xFFFFFFFF.

The code in the main branch, I wrote PR #28673 to fix it instead.