[Vm-dev] Debugging the new compactor and the SocketPlugin ;-)

[Eliot Miranda]

Hi All,

    I'm having a blast writing and debugging the new compactor.  I've got
to the stage where, in a real VM, I can load and save images and run global
garbage collect fairly reliably, but when I go through a sequence of

    check changes on a package in the Monticello Browser
    attempt to save these changes
    receive warning that there's a more up-to-date version
    update the image

I reliably get a crash.

Now in the simulator I'm using lemming debugging to be able to endlessly
repeat a failing GC, with the original heap unchanged as a reference, hence
having a blast, cuz this makes it relatively easy to debug.  But in the
real VM I would have to implement a fair ammount to reproduce lemming
debugging

    - forking the process on GC
    - running the GC in the child
    - catching the exit status
    - raising an exception in the parent to allow the debugger to attach
    - being able to proceed from the exception by repeating the fork and
the GC, etc...

And yet if and when I did this I would still have nothing like the
debuggability I have in the simulator.

To be able to reproduce the original sequent in the Simulator I also need a
fair amount, to be specific, I need a simulate able SocketPlugin.  This
means implementing some subset of #sqResolverAbort
#sqResolverAddrLookup:Result: #sqResolverAddrLookupResultSize
#sqResolverError #sqResolverGetAddressInfoFamily
#sqResolverGetAddressInfoHost:Size:Service:Size:Flags:Family:Type:Protocol:
#sqResolverGetAddressInfoNext #sqResolverGetAddressInfoProtocol
#sqResolverGetAddressInfoResult:Size: #sqResolverGetAddressInfoSize
#sqResolverGetAddressInfoType #sqResolverGetNameInfo:Size:Flags:
#sqResolverGetNameInfoHostResult:Size: #sqResolverGetNameInfoHostSize
#sqResolverGetNameInfoServiceResult:Size: #sqResolverGetNameInfoServiceSize
#sqResolverHostNameResult:Size: #sqResolverHostNameSize
#sqResolverLocalAddress #sqResolverNameLookupResult
#sqResolverStartAddrLookup: #sqResolverStartName:Lookup: #sqResolverStatus
#sqSocket:AcceptFrom:RecvBytes:SendBytes:SemaID:
#sqSocket:AcceptFrom:RecvBytes:SendBytes:SemaID:ReadSemaID:WriteSemaID:
#sqSocket:BindTo:Port: #sqSocket:BindToAddress:Size:
#sqSocket:ConnectTo:Port: #sqSocket:ConnectToAddress:Size:
#sqSocket:CreateNetType:SocketType:RecvBytes:SendBytes:SemaID:
#sqSocket:CreateNetType:SocketType:RecvBytes:SendBytes:SemaID:ReadSemaID:WriteSemaID:
#sqSocket:CreateRaw:ProtoType:RecvBytes:SendBytes:SemaID:ReadSemaID:WriteSemaID:
#sqSocket:ListenBacklog: #sqSocket:ListenOnPort:
#sqSocket:ListenOnPort:BacklogSize:
#sqSocket:ListenOnPort:BacklogSize:Interface:
#sqSocket:LocalAddressResult:Size: #sqSocket:ReceiveDataBuf:Count:
#sqSocket:ReceiveUDPDataBuf:Count:address:port:moreFlag:
#sqSocket:RemoteAddressResult:Size: #sqSocket:SendDataBuf:Count:
#sqSocket:toHost:port:SendDataBuf:Count: #sqSocketAbortConnection:
#sqSocketAddress:Size:SetPort: #sqSocketAddress:SizeGetPort:
#sqSocketCloseConnection: #sqSocketConnectionStatus: #sqSocketDestroy:
#sqSocketError:
#sqSocketGetOptions:optionNameStart:optionNameSize:returnedValue:
#sqSocketLocalAddress: #sqSocketLocalAddressSize: #sqSocketLocalPort:
#sqSocketReceiveDataAvailable: #sqSocketRemoteAddress:
#sqSocketRemoteAddressSize: #sqSocketRemotePort: #sqSocketSendDone:
#sqSocketSetOptions:optionNameStart:optionNameSize:optionValueStart:optionValueSize:returnedValue:

;-)

(BTW, the implementation strategy, as it is with the FilePluginSmulator, is
to fall back on the host image's facilities; probably simpler with the
SocketPlugin than the FilePlugin because there's no need to fake up
directory entries and the like - at least I hope so).

Now being able to simulate images that use sockets is probably quite
useful.  And I'm leaning toads having a go, but have no idea how long its
going to take (I don't know the subset of the above that will need to be
implemented to get image update to simulate fully).

So has anyone else had any experience here?  Got a SocketPluginSimulator
you've hidden away for a rainy day?  Think its way too difficult and I
should implement lemming debugging for real?
_,,,^..^,,,_
best, Eliot
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