Lyric

What changed in v4.0.1 — 2026-08-27

The sweep after 4.0.0. Eight probes against what the major added; four real findings, all fixed failing-test-first. Nothing in the language or the format changed.

Fixed

• A read of a CLOSED socket no longer crashes the process. netReadReady answered "no bytes" for a descriptor the table does not know without recording a reason, so the previous call's would-block stood and readSome went back to the scheduler to wait on a descriptor nothing could ever ready. poll then selected on a list that resolved to nothing, and Socket.Select threw — an unhandled host exception, printed as a .NET stack trace, which is precisely what the panic doctrine exists to prevent. Now: an unresolvable descriptor is a recorded failure (so the silent form answers null and the twin names it), and poll names a dead descriptor READY at once — the convention an errored socket already followed, since the wake exists so the next read can tell the waiter what happened.
• An import used through its SECOND overload is no longer reported as unused (LYR-SEM0072). Importing a name brings the whole set, but the accounting looked only at its first member — so import std.io.net { bind, localPort, close }; warned about names the file demonstrably calls, and under --deny-warnings that breaks a build for correct code.
• One VM's interrupt() no longer reaches another VM's tasks. The pending flag was process-wide, while the socket table beside it is per-thread for exactly the opposite reason. The SIGNAL stays process-wide — SIGINT means the process — but the programmatic raise is now per VM.
• A second VM no longer clears the first one's interrupt listening. The flag was assigned on every poll, so a VM without a parked task turned Ctrl+C back into a process kill while another VM was waiting for it. Listening is counted now, and the count moves on transitions.
• A sleep beyond ~292 million years no longer waits forever. The millisecond-to-microsecond conversion overflowed into a negative number, which Select reads as "no deadline"; the clamp now happens before the multiplication.

The full changelog →