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Avoid assertion for legitimate case where reply received for handler that was closed #1437

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rconnell9 merged 4 commits into from
Jun 5, 2026
Merged

Avoid assertion for legitimate case where reply received for handler that was closed #1437

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Avoid assertion for legitimate case where reply received for handler …
rconnell9 Jun 1, 2026
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rconnell9 Jun 1, 2026
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rconnell9 Jun 3, 2026
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rconnell9 Jun 5, 2026
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24 changes: 15 additions & 9 deletions Sources/SwiftBuild/SWBBuildServiceConnection.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,12 @@ typealias swb_build_service_connection_message_handler_t = @Sendable (UInt64, SW

/// Track whether the channels have been cleared because the service has crashed.
var channelsHaveBeenCleared = false

/// A nil handler for a known channel is expected, service crash or client closed the channel before the reply arrived.
/// A nil handler for an unknown channel is unexpected.
func isChannelKnown(_ channel: UInt64) -> Bool {
return channel <= nextChannelID
}
}

/// An "unfair lock" that protects the channels state. Should be held only for very short periods of time.
Expand Down Expand Up @@ -303,14 +309,6 @@ typealias swb_build_service_connection_message_handler_t = @Sendable (UInt64, SW
let channel = headerFrame.channel
let msgSize = Int(headerFrame.messageSize)

// Look up the channel by its number.
let handler = self.channelState.withLock({ $0.channels[channel] })
if handler == nil {
// It’s an error if we didn’t find a channel here.
// FIXME: We need to handle this error in a better way.
assertionFailure("no handler for channel: \(channel)")
}

// If we don’t have all the data yet, we can go no further.
if offset + msgSize > data.count {
// Move the offset back to just before the header, so we’ll see it again next time around.
Expand All @@ -320,7 +318,15 @@ typealias swb_build_service_connection_message_handler_t = @Sendable (UInt64, SW
}

// Otherwise, look up the channel by its number.
handler?(channel, data.subdata(in: offset..<(offset + msgSize)))
let (handler, isChannelKnown) = self.channelState.withLock {
return ($0.channels[channel], $0.isChannelKnown(channel))
}

if let handler {
handler(channel, data.subdata(in: offset..<(offset + msgSize)))
} else {
assert(isChannelKnown, "Received reply for unknown channel: \(channel)")
}

// Move on to the next message.
offset += msgSize
Expand Down
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