forked from unom/punktfunk
`CudaHw::new` and `VaapiHw::new` are the same shape — alloc a hwdevice, deref it to fill fields, init, alloc a frames ctx, deref, init — and both unwound by hand: `av_buffer_unref` on every failure branch (three in CUDA, two in VAAPI) plus a hand-written `Drop` repeating the pair. That shape has two failure modes and the compiler can see neither: add a branch and forget the cleanup (leak), or let two cleanup paths run (double-unref, an abort inside glibc). `libav::AvBuffer` owns the ref instead. It null-checks on the way in — the check each caller open-coded — and unrefs exactly once on drop, so an early `?` releases whatever was built so far and the failure branches carry no cleanup at all. Both hand-written `Drop` impls are gone, and `linux/mod.rs` goes from seven `av_buffer_unref` calls to zero. The one subtlety, called out at both structs: these two fields must stay declared frames-BEFORE-device. Fields drop in declaration order, and the code being replaced deliberately unref'd frames first (a frames ctx holds its own reference on its device). Refcounting makes either order sound, but a field reorder should not silently change what ships, so the ordering is load-bearing and commented as such. Also adds `cuda_hw_alloc_drop_cycles` — the RAII path had NO test coverage: the NVENC smoke tests take the CPU path and never construct a `CudaHw`, and the VAAPI twin's tests need AMD/Intel silicon. Looping construct/drop is what catches the double-unref (abort) and the leak (allocator growth) this refactor is about. Verified on Nobara (RTX 5070 Ti): `cargo check -p pf-encode --all-targets` clean at exit 0, `cargo test -p pf-encode` 33 passed / 0 failed, and `cuda_hw_alloc_drop_cycles` passes against a real CUDA device — eight construct/drop cycles, no abort. `VaapiHw` is compile-verified only; it is the identical shape but no AMD/Intel box was reachable to run its two ignored tests.