Continuation zero alloc enqueue#305
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sgerbino merged 3 commits intoJul 2, 2026
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capy removed the DynamicBuffer concept, string_dynamic_buffer, and read_until, so several corosio targets no longer compile against the current capy. Migrate them to the fixed-buffer read primitives: - tcp_socket unit test: read a fixed number of bytes into a mutable_buffer instead of a string_dynamic_buffer. - http-client and https-client examples: read the response until EOF one fixed chunk at a time. - corosio http_server benchmark: a local read_until helper scans for the header delimiter over single reads, preserving the previous read-until semantics.
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An automated preview of the documentation is available at https://305.corosio.prtest3.cppalliance.org/index.html If more commits are pushed to the pull request, the docs will rebuild at the same URL. 2026-07-02 21:18:57 UTC |
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Posting a capy::continuation no longer recovers an enclosing continuation_op through offset-based pointer arithmetic and a magic tag. That recovery read out of bounds whenever a bare continuation (one not embedded in a continuation_op) was posted. The bare continuation is now the unit that is enqueued directly, so the read is gone. A new detail::ready_queue is a single intrusive FIFO that carries both scheduler_ops and capy::continuations, distinguished by a low tag bit on each queue entry. The bit is stolen from the guaranteed-zero low bit of an aligned pointer and decoded with std::bit_cast, so there is no integer-to-pointer cast and no strict-aliasing violation. A scheduler_op links through a uintptr_t q_next_ that reuses its former padding word; a continuation links through capy's reserved slot. The scheduler gains a post(capy::continuation&) overload that enqueues the continuation with no heap allocation. The reactor, io_uring, and IOCP ready paths all carry continuations. Each drain loop decodes the tag and either resumes the coroutine handle or dispatches the op; each shutdown drain destroys the coroutine frame instead of resuming it. IOCP routes a continuation through the completion port under a dedicated key_continuation key. Posted coroutines resume without memory fences: every ready-queue publish and pop is ordered by the scheduler's mutex, and on IOCP by the completion port's kernel transition, so the cross-thread handoff is fully visible to ThreadSanitizer. continuation_op is removed; every embedder now stores a bare capy::continuation directly. Unit tests cover the ready_queue ordering, a worst-case-layout reproducer for the former out-of-bounds read, and a counting-operator- new assertion that the reactor and io_uring post paths allocate nothing.
The capy checkout pinned every ref except master to capy develop, so branches tracking a different capy line, such as develop-2, built against a mismatched dependency. A resolve step now picks the first capy branch whose name matches the build: the pull request's source, then its target, then the pushed branch, falling back to capy's default branch. Trigger filters use a develop* glob so develop-2 pushes and pull requests run CI, docs, and coverage. The boost and asio checkouts are unchanged; neither tracks a develop-2 line.
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Resolves #290.