`pf-win-display`'s 21 CCD/GDI helpers were `pub unsafe fn` without a memory-safety
obligation between them. Every one takes `Copy` scalars or borrowed Rust data, returns
owned values, and discharges its FFI preconditions internally —
`retry_set_display_config` even binds the input desktop itself, which is the one thing
a caller could plausibly get wrong. Their own `# Safety` sections say as much: one
reads "safe to call from any thread", and the rest say "call under the manager `state`
lock". That is a SERIALIZATION requirement — calling one unlocked races the topology
mutator and returns a stale answer, a correctness bug, not undefined behaviour.
Encoding it with `unsafe fn` cost 55 `unsafe` blocks across THREE crates whose proofs
could only restate "this takes a u32 and returns a String". That is how `unsafe` stops
meaning anything: the blocks that wrap a real FFI obligation read exactly like the ones
that wrap nothing. The requirement is now prose on the functions that have it, and
`unsafe` marks only the FFI calls inside the helpers.
win_display.rs 97 -> 63 `unsafe`, manager.rs 56 -> 30, pf_vdisplay.rs 34 -> 32, plus 10
sites in pf-capture's IDD-push paths. 55 blocks and 55 orphaned `// SAFETY:` proofs
gone; `#![allow(clippy::missing_safety_doc)]` with them, since nothing is `pub unsafe
fn` any more.
Two things the compiler handed back once the blocks went, both of which existed only to
carry a proof: the `let-else` parens in `force_mode_reenumeration` and
`apply_source_positions`, and the nested `if` in `wait_mode_settled` — which is `&&`
again, still short-circuiting, so the second CCD query on a 25 ms poll is unchanged.
Scope note: the sweep and the plan both scoped this as two crates. It is three —
pf-capture calls the same helpers from 10 sites, and `unused_unsafe` under `-D warnings`
makes that non-optional. Found by re-deriving the count, which the plan asked for
because the underlying finding had been REFUTED in verification; the refutation was
wrong about the magnitude (22 of manager.rs's 45 blocks, against its claimed 24).
Verified on the Windows runner: clippy --all-targets clean over pf-frame,
pf-win-display, pf-capture and pf-vdisplay; pf-vdisplay 55 passed, pf-capture 18 passed.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
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