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Fix build break - #136388
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Fix build break#136388
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jkotas
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October 23, 2026 22:11
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Azure Pipelines: Successfully started running 5 pipeline(s). 11 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run. |
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
lewing
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Oct 23, 2026
steveisok
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Oct 23, 2026
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Oops, sorry, I had it in mind, but forgot when I merged the 2nd PR 😞 |
EgorBo
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Oct 23, 2026
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I think it should be safe to merge it as is to unblock others |
EgorBo
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October 23, 2026 22:38
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/ba-g fast merge build break |
lewing
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October 23, 2026 22:39
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Oct 26, 2026
On Unix, a zero-byte receive is implemented as a 1-byte `MSG_PEEK`. wasi-libc rejects `MSG_PEEK` with `EOPNOTSUPP`, so every zero-byte receive fails on WASI. Callers such as HTTP/2 in `SocketsHttpHandler` rely on zero-byte reads to wait for data. This was split out of #136234 at a reviewer's request. ## Fix On WASI, a zero-byte receive with no flags now does this instead: - It polls the socket for `POLLIN` with a zero timeout, and completes only when the socket is readable. - If the socket can't be polled, it does a zero-length `recv` so the real error is reported. For example, wasi-libc returns `EOPNOTSUPP` for an unconnected TCP socket, and the `recv` reports `ENOTCONN` instead. - WASI poll events don't say which direction is ready, so queued zero-byte receives re-run this check. They no longer complete on any event. Non-WASI behavior is unchanged. Not covered: a zero-byte `ReceiveFrom`/`ReceiveMessageFrom` that passes an endpoint still takes the `MSG_PEEK` path on WASI. ## Known caveat After data has been drained, one zero-byte receive can complete early, because wasmtime keeps readiness set until a read would block. wasmtime treats this as by design (bytecodealliance/wasmtime#9667). The next real read then waits correctly. ## Validation - **CoreCLR WASI, Release, wasmtime 49.0.1:** the full System.Net.Sockets functional tests ran 653 tests: 565 passed, 0 failed, 88 skipped. The baseline on main is about 645 run with 0 failed. The two new tests passed in all 4 variants that run on WASI. - **macOS, Release:** I ran the `SendReceive_*` classes (Sync, SyncForceNonBlocking, Apm, Task, Eap, SpanSync, MemoryArrayTask, MemoryNativeTask). Total was 252 with 0 failed, and both new tests passed in every variant. - `Receive0Byte_NotConnected_Throws` runs on all platforms. `Receive0Byte_Udp_CompletesWhenDatagramArrives` runs on Unix only, because on Windows a zero-byte receive consumes the datagram. - `SocketsHttpHandler`/HTTP/2 isn't enabled on WASI in main, so the motivating HTTP/2 scenario is covered in #136234 rather than here. - Building main locally needed the `fgopt.cpp` fix from #136388. That fix is not part of this PR. Related: #107981 > [!NOTE] > This PR was generated with GitHub Copilot. --------- Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Conflict between #136263 and earlier PR