Am 22. Nov 2001 um 16:22 MET schrieb Simon Marlow:

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I'm sad to say there was another bug in SocketPrim.getSocketOption in 5.02.1. Please try the enclosed patch.

How does this explain the two differing behaviours? And why didn't it happen in a compiled version?

Because the 'optlen' parameter to getsockopt was wrong (1 instead of sizeof(int)), which means that the other 3 bytes would be garbage. If the other 3 bytes happened to be zero, you probably wouldn't notice. Anyway, I've tested this with the latest sources and it seems to work, whereas I can repro the bug with 5.02.1 in GHCi. Cheers, Simon