Macro trace_call 

macro_rules! trace_call {
    ($name:literal, $a:expr, $b:expr, $call:block) => { ... };
}

Bracket a Win32 call that blocks, or that takes a lock inside the pool.

Records the call’s name under syscall-enter before it and syscall-leave after, so a call that blocked shows up as an interval rather than as a record with a later timestamp than you expected. The difference matters: a single record stamped after the call returns cannot distinguish “this was issued late” from “this took four seconds to return”.

Every thread-pool API touches the pool’s own synchronisation, and several block outright – the WaitForThreadpool*Callbacks family, CloseThreadpoolCleanupGroupMembers, CloseThreadpool, and SetThreadpoolThreadMinimum, which creates threads. Which of the rest can contend is not documented, so they are bracketed too rather than assumed cheap: the whole point is to catch synchronisation nobody expected.

It is its own target, so it can be switched on without it. A capture narrowed to wait,delivery is unchanged by this existing; one narrowed to syscall sees only the call boundaries. Argument expressions are evaluated only when the target is being traced, and the whole thing compiles to the call alone without the trace feature.

crate::trace_call!("SetThreadpoolWait", wait, handle as usize, {
    // SAFETY: ...
    unsafe { SetThreadpoolWait(wait, handle, ptr::null()) }
})