Squeak-dev October 2014

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The Inbox: Files-ul.141.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of Files was added to project The Inbox: http://source.squeak.org/inbox/Files-ul.141.mcz ==================== Summary ==================== Name: Files-ul.141 Author: ul Time: 27 October 2014, 4:51:14.305 pm UUID: b0dbabfe-ce75-4f18-a82f-2f95fa8b026e Ancestors: Files-eem.138 - use the new ExternalObjectTable API =============== Diff against Files-eem.138 =============== Item was changed: ----- Method: AsyncFile>>open:forWrite: (in category 'as yet unclassified') ----- open: fullFileName forWrite: aBoolean "Open a file of the given name, and return a handle for that file. Answer the receiver if the primitive succeeds, nil otherwise. If openForWrite is true, then: if there is no existing file with this name, then create one else open the existing file in read-write mode otherwise: if there is an existing file with this name, then open it read-only else answer nil." "Note: if an exisiting file is opened for writing, it is NOT truncated. If truncation is desired, the file should be deleted before being opened as an asynchronous file." "Note: On some platforms (e.g., Mac), a file can only have one writer at a time." - | semaIndex | name := fullFileName. writeable := aBoolean. + ^Smalltalk newExternalSemaphoreDo: [ :newSemaphore :index | + fileHandle := self primOpen: name asVmPathName forWrite: writeable semaIndex: index. + fileHandle + ifNotNil: [ + semaphore := newSemaphore. + self ] + ifNil: [ + Smalltalk unregisterExternalObject: newSemaphore. + nil ] ]! - semaphore := Semaphore new. - semaIndex := Smalltalk registerExternalObject: semaphore. - fileHandle := self primOpen: name asVmPathName forWrite: writeable semaIndex: semaIndex. - fileHandle ifNil: [ - Smalltalk unregisterExternalObject: semaphore. - semaphore := nil. - ^ nil]. - ! Item was changed: ----- Method: StandardFileStream>>post:target:url:ifError: (in category 'browser requests') ----- post: data target: target url: url ifError: errorBlock "Post data to the given URL. The returned file stream contains the reply of the server. If Squeak is not running in a browser evaluate errorBlock" + - | sema index request result | self waitBrowserReadyFor: self defaultBrowserReadyWait ifFail: [^errorBlock value]. + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + | request result | + request := self primURLPost: url target: target data: data semaIndex: index. + request ifNil: [ + Smalltalk unregisterExternalObject: semaphore. + ^errorBlock value ]. + [ semaphore wait. "until something happens" + result := self primURLRequestState: request. + result == nil ] whileTrue. + result ifTrue: [ fileID := self primURLRequestFileHandle: request ]. - sema := Semaphore new. - index := Smalltalk registerExternalObject: sema. - request := self primURLPost: url target: target data: data semaIndex: index. - request == nil ifTrue:[ - - Smalltalk unregisterExternalObject: sema. - ^errorBlock value. - ] ifFalse:[ - [sema wait. "until something happens" - result := self primURLRequestState: request. - result == nil] whileTrue. - result ifTrue:[fileID := self primURLRequestFileHandle: request]. self primURLRequestDestroy: request. + Smalltalk unregisterExternalObject: semaphore ]. + fileID ifNil: [ ^nil ]. - ]. - Smalltalk unregisterExternalObject: sema. - fileID == nil ifTrue:[^nil]. self register. name := url. rwmode := false. buffer1 := String new: 1. + self enableReadBuffering! - self enableReadBuffering - ! Item was changed: ----- Method: StandardFileStream>>requestURL:target:ifError: (in category 'browser requests') ----- requestURL: url target: target ifError: errorBlock "Request to go to the target for the given URL. If Squeak is not running in a browser evaluate errorBlock" - | sema index request result | self waitBrowserReadyFor: self defaultBrowserReadyWait ifFail: [^errorBlock value]. + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + | request result | + request := self primURLRequest: url target: target semaIndex: index. + request ifNil: [ + Smalltalk unregisterExternalObject: semaphore. + ^errorBlock value ]. + [ semaphore wait. "until something happens" + result := self primURLRequestState: request. + result == nil ] whileTrue. - sema := Semaphore new. - index := Smalltalk registerExternalObject: sema. - request := self primURLRequest: url target: target semaIndex: index. - request == nil ifTrue:[ - - Smalltalk unregisterExternalObject: sema. - ^errorBlock value. - ] ifFalse:[ - [sema wait. "until something happens" - result := self primURLRequestState: request. - result == nil] whileTrue. self primURLRequestDestroy: request. + Smalltalk unregisterExternalObject: semaphore ]. + fileID ifNil: [ ^nil ]. - ]. - Smalltalk unregisterExternalObject: sema. - fileID == nil ifTrue:[^nil]. self register. name := url. rwmode := false. buffer1 := String new: 1. + self enableReadBuffering! - self enableReadBuffering - ! Item was changed: ----- Method: StandardFileStream>>requestURLStream:ifError: (in category 'browser requests') ----- requestURLStream: url ifError: errorBlock "Request a FileStream for the given URL. If Squeak is not running in a browser evaluate errorBlock" "FileStream requestURLStream:'http://www.squeak.org'" + - | sema index request result | self waitBrowserReadyFor: self defaultBrowserReadyWait ifFail: [^errorBlock value]. + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + | request result | + request := self primURLRequest: url semaIndex: index. + request ifNil: [ + Smalltalk unregisterExternalObject: semaphore. + ^errorBlock value ]. + [ semaphore wait. "until something happens" + result := self primURLRequestState: request. + result == nil ] whileTrue. + result ifTrue: [ fileID := self primURLRequestFileHandle: request ]. - sema := Semaphore new. - index := Smalltalk registerExternalObject: sema. - request := self primURLRequest: url semaIndex: index. - request == nil ifTrue:[ - - Smalltalk unregisterExternalObject: sema. - ^errorBlock value. - ] ifFalse:[ - [sema wait. "until something happens" - result := self primURLRequestState: request. - result == nil] whileTrue. - result ifTrue:[fileID := self primURLRequestFileHandle: request]. self primURLRequestDestroy: request. + Smalltalk unregisterExternalObject: semaphore ]. + fileID ifNil: [ ^nil ]. - ]. - Smalltalk unregisterExternalObject: sema. - fileID == nil ifTrue:[^nil]. self register. name := url. rwmode := false. buffer1 := String new: 1. + self enableReadBuffering! - self enableReadBuffering - !

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The Inbox: Network-ul.155.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of Network was added to project The Inbox: http://source.squeak.org/inbox/Network-ul.155.mcz ==================== Summary ==================== Name: Network-ul.155 Author: ul Time: 27 October 2014, 4:46:13.635 pm UUID: cf2f8a25-3525-4183-8f93-7dc5d127f22d Ancestors: Network-ul.152 - use the new ExternalObjectTable API - unifed socket initialization - unregister ResolverSemaphore when the network initialization fails =============== Diff against Network-ul.152 =============== Item was changed: ----- Method: NetNameResolver class>>initializeNetwork (in category 'network initialization') ----- initializeNetwork "Initialize the network drivers and record the semaphore to be used by the resolver. Do nothing if the network is already initialized. Evaluate the given block if network initialization fails." "NetNameResolver initializeNetwork" - | semaIndex | self resolverStatus = ResolverUninitialized ifFalse: [^HaveNetwork := true]. "network is already initialized" HaveNetwork := false. "in case abort" + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + ResolverSemaphore := semaphore. + "result is nil if network initialization failed, self if it succeeds" + (self primInitializeNetwork: index) + ifNil: [ + Smalltalk unregisterExternalObject: ResolverSemaphore. + ResolverSemaphore := nil. + NoNetworkError signal: 'failed network initialization'] + ifNotNil: [ HaveNetwork := true ] ]. - ResolverSemaphore := Semaphore new. - semaIndex := Smalltalk registerExternalObject: ResolverSemaphore. + self initializeOldNetworkFlag! - "result is nil if network initialization failed, self if it succeeds" - (self primInitializeNetwork: semaIndex) - ifNil: [NoNetworkError signal: 'failed network initialization'] - ifNotNil: [HaveNetwork := true]. - - self initializeOldNetworkFlag - ! Item was changed: ----- Method: Socket>>acceptFrom: (in category 'initialize-destroy') ----- acceptFrom: aSocket "Initialize a new socket handle from an accept call" - | semaIndex readSemaIndex writeSemaIndex | + self initializeSocketHandleUsing: [ :semaIndex :readSemaIndex :writeSemaIndex | + self + primAcceptFrom: aSocket socketHandle + receiveBufferSize: 8000 + sendBufSize: 8000 + semaIndex: semaIndex + readSemaIndex: readSemaIndex + writeSemaIndex: writeSemaIndex ]! - semaphore := Semaphore new. - readSemaphore := Semaphore new. - writeSemaphore := Semaphore new. - semaIndex := Smalltalk registerExternalObject: semaphore. - readSemaIndex := Smalltalk registerExternalObject: readSemaphore. - writeSemaIndex := Smalltalk registerExternalObject: writeSemaphore. - socketHandle := self primAcceptFrom: aSocket socketHandle - receiveBufferSize: 8000 - sendBufSize: 8000 - semaIndex: semaIndex - readSemaIndex: readSemaIndex - writeSemaIndex: writeSemaIndex. - socketHandle - ifNotNil: [ self register ] - ifNil: [ "socket creation failed" - Smalltalk unregisterExternalObject: semaphore. - Smalltalk unregisterExternalObject: readSemaphore. - Smalltalk unregisterExternalObject: writeSemaphore. - readSemaphore := writeSemaphore := semaphore := nil ] - ! Item was changed: ----- Method: Socket>>destroy (in category 'initialize-destroy') ----- destroy "Destroy this socket. Its connection, if any, is aborted and its resources are freed. Do nothing if the socket has already been destroyed (i.e., if its socketHandle is nil)." socketHandle ifNotNil: [ self isValid ifTrue: [ self primSocketDestroy: socketHandle ]. + Smalltalk unregisterExternalObjects: { + semaphore. + readSemaphore. + writeSemaphore }. - Smalltalk unregisterExternalObject: semaphore. - Smalltalk unregisterExternalObject: readSemaphore. - Smalltalk unregisterExternalObject: writeSemaphore. socketHandle := nil. readSemaphore := writeSemaphore := semaphore := nil. self unregister ]! Item was changed: ----- Method: Socket>>finalize (in category 'finalization') ----- finalize + self primSocketDestroyGently: socketHandle. + Smalltalk unregisterExternalObjects: { + semaphore. + readSemaphore. + writeSemaphore } - Smalltalk unregisterExternalObject: semaphore. - Smalltalk unregisterExternalObject: readSemaphore. - Smalltalk unregisterExternalObject: writeSemaphore. ! Item was changed: ----- Method: Socket>>initialize: (in category 'initialize-destroy') ----- initialize: socketType "Initialize a new socket handle. If socket creation fails, socketHandle will be set to nil." - | semaIndex readSemaIndex writeSemaIndex | + self initializeSocketHandleUsing: [ :semaIndex :readSemaIndex :writeSemaIndex | - semaphore := Semaphore new. - readSemaphore := Semaphore new. - writeSemaphore := Semaphore new. - semaIndex := Smalltalk registerExternalObject: semaphore. - readSemaIndex := Smalltalk registerExternalObject: readSemaphore. - writeSemaIndex := Smalltalk registerExternalObject: writeSemaphore. - socketHandle := self primSocketCreateNetwork: 0 type: socketType receiveBufferSize: 8000 sendBufSize: 8000 semaIndex: semaIndex readSemaIndex: readSemaIndex + writeSemaIndex: writeSemaIndex ]! - writeSemaIndex: writeSemaIndex. - - socketHandle - ifNotNil: [ self register ] - ifNil: [ "socket creation failed" - Smalltalk unregisterExternalObject: semaphore. - Smalltalk unregisterExternalObject: readSemaphore. - Smalltalk unregisterExternalObject: writeSemaphore. - readSemaphore := writeSemaphore := semaphore := nil ] - ! Item was changed: ----- Method: Socket>>initialize:family: (in category 'initialize-destroy') ----- initialize: socketType family: family "Initialize a new socket handle. If socket creation fails, socketHandle will be set to nil." - | semaIndex readSemaIndex writeSemaIndex | + NetNameResolver useOldNetwork ifTrue: [ ^self initialize: socketType ]. + self initializeSocketHandleUsing: [ :semaIndex :readSemaIndex :writeSemaIndex | - NetNameResolver useOldNetwork ifTrue: [^self initialize: socketType]. - semaphore := Semaphore new. - readSemaphore := Semaphore new. - writeSemaphore := Semaphore new. - semaIndex := Smalltalk registerExternalObject: semaphore. - readSemaIndex := Smalltalk registerExternalObject: readSemaphore. - writeSemaIndex := Smalltalk registerExternalObject: writeSemaphore. - socketHandle := self primSocketCreateNetwork: family type: socketType receiveBufferSize: 8000 sendBufSize: 8000 semaIndex: semaIndex readSemaIndex: readSemaIndex + writeSemaIndex: writeSemaIndex ]! - writeSemaIndex: writeSemaIndex. - - socketHandle - ifNotNil: [ self register ] - ifNil: [ "socket creation failed" - Smalltalk unregisterExternalObject: semaphore. - Smalltalk unregisterExternalObject: readSemaphore. - Smalltalk unregisterExternalObject: writeSemaphore. - readSemaphore := writeSemaphore := semaphore := nil ] - ! Item was added: + ----- Method: Socket>>initializeSocketHandleUsing: (in category 'initialize-destroy') ----- + initializeSocketHandleUsing: aBlock + "Initialize a new socket handle. If socket creation fails, socketHandle will be set to nil." + + | semaphoresAndIndexes semaphores indexes | + semaphoresAndIndexes := Smalltalk newExternalSemaphores: 3. + semaphores := semaphoresAndIndexes at: 1. + indexes := semaphoresAndIndexes at: 2. + semaphore := semaphores at: 1. + readSemaphore := semaphores at: 2. + writeSemaphore := semaphores at: 3. + (socketHandle := aBlock valueWithArguments: indexes) + ifNotNil: [ self register ] + ifNil: [ + "socket creation failed" + semaphore := readSemaphore := writeSemaphore := nil. + Smalltalk unregisterExternalObjects: semaphores ]!

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The Inbox: System-ul.688.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of System was added to project The Inbox: http://source.squeak.org/inbox/System-ul.688.mcz ==================== Summary ==================== Name: System-ul.688 Author: ul Time: 27 October 2014, 4:43:14.279 pm UUID: 77747387-55a5-4118-95b5-752979bf1cf7 Ancestors: System-dtl.685 Replaced ExternalSemaphoreTable with ExternalObjectTable to provide faster registration, and give better support to the current users of external objects. Notable changes: - the table is a separate object instead of a few class side methods - the whole API can be found in SmalltalkImage in the external objects category - #newExternalSemaphore, #newExternalSemaphoreDo: and #newExternalSemaphores: provide fast and easy creation and registration of Semaphores - #unregisterExternalObjects: can unregister multiple objects faster - #externalObjects will return a copy of the externalObjectsArray - better scalability - the maxExternalSemaphores VM parameter will be incremented as the externalObjectsArray grows =============== Diff against System-dtl.685 =============== Item was added: + Object subclass: #ExternalObjectTable + instanceVariableNames: 'semaphore externalObjectsArray freeSlotIndexes indexesByObjects' + classVariableNames: '' + poolDictionaries: '' + category: 'System-Support'! + ExternalObjectTable class + instanceVariableNames: 'current'! + + !ExternalObjectTable commentStamp: 'ul 10/27/2014 16:26' prior: 0! + I'm an enhanced version of JMM's ExternalSemaphoreTable. + I'm responsible for maintaining the externalObjectsArray, which can be found at slot 39 of Smalltalk specialObjectsArray. Manipulating the array directly is highly discouraged. + + My services are available via the methods of the "external objects" category of SmalltalkImage. + + To register anObject simply use Smalltalk registerExternalObject: anObject. Use #unregisterExternalObject: to unregister it. It your responsibility to always unregister these objects. + If you'd like the create one or more new Semaphores, and register them for external use, then you should use one of #newExternalSemaphore, #newExternalSemaphoreDo: and #newExternalSemaphores:. If you want to unregister more than one external objects at the same time, then #unregisterExternalObjects: is the method you're looking for. + + Implementation details: + I maintain a single instance (#current), which can automatically synchronize with externalObjectsArray. + All accesses are protected by the semaphore instance variable. + To ensure fast access, I keep track of the indexes of the external objects in the externalObjectArray in my indexesByObjects IdentityDictionary. + To ensure fast insertion, I keep track of the free slots of the externalObjectsArray in the freeSlotIndexes OrderedCollection. The access pattern is LIFO to avoid unnecessary growth and reordering of the OrderedCollection. + I can grow the externalObjectsArray (see #ensureFreeSlot), but I never shrink it.! + ExternalObjectTable class + instanceVariableNames: 'current'! Item was added: + ----- Method: ExternalObjectTable class>>cleanUp: (in category 'initialize-release') ----- + cleanUp: aggressive + "It's safe to release the instance" + + self reset! Item was added: + ----- Method: ExternalObjectTable class>>current (in category 'accessing') ----- + current + + ^current ifNil: [ + | newInstance | + newInstance := self new. + " Check again, because another process might have registered another instance. " + current ifNil: [ current := newInstance ] ]! Item was added: + ----- Method: ExternalObjectTable class>>reset (in category 'accessing') ----- + reset + + current := nil! Item was added: + ----- Method: ExternalObjectTable>>clearExternalObjects (in category 'accessing') ----- + clearExternalObjects + "Clear the array of objects that have been registered for use in non-Smalltalk code." + + semaphore critical: [ + Smalltalk specialObjectsArray at: 39 put: Array new. + self + initializeCaches; + synchronizeExternalObjectsArrayAndForceUpdate: true ]! Item was added: + ----- Method: ExternalObjectTable>>ensureFreeSlot (in category 'private') ----- + ensureFreeSlot + "Make sure there's at least one free slot." + + | oldSize newSize newExternalObjectsArray specialObjectsArray | + freeSlotIndexes isEmpty ifFalse: [ ^self ]. + oldSize := externalObjectsArray size. + newSize := oldSize + 20. "Linear growth is not really a problem, because we never shrink the array." + newExternalObjectsArray := externalObjectsArray species new: newSize. + newExternalObjectsArray + replaceFrom: 1 + to: oldSize + with: externalObjectsArray + startingAt: 1. + specialObjectsArray := Smalltalk specialObjectsArray. + (specialObjectsArray at: 39) == externalObjectsArray + ifFalse: [ + "We're not in sync. Try again." + ^self + synchronizeExternalObjectsArrayAndForceUpdate: true; + ensureFreeSlot ]. + specialObjectsArray at: 39 put: newExternalObjectsArray. + externalObjectsArray := newExternalObjectsArray. + newSize to: oldSize + 1 by: -1 do: [ :each | + freeSlotIndexes addFirst: each ]. + Smalltalk maxExternalSemaphores ifNotNil: [ :maxExternalSemaphores | + "Make sure that those new external semaphores can be signaled by the VM. This is not entirely safe, but not incrementing at all is worse." + newSize > maxExternalSemaphores ifTrue: [ + Smalltalk maxExternalSemaphores: newSize ] ] + + ! Item was added: + ----- Method: ExternalObjectTable>>externalObjects (in category 'accessing') ----- + externalObjects + "Return a copy of the externalObjectsArray." + + ^semaphore critical: [ + self synchronizeExternalObjectsArrayAndForceUpdate: false. + externalObjectsArray copy ]! Item was added: + ----- Method: ExternalObjectTable>>externalObjectsArray: (in category 'private') ----- + externalObjectsArray: anArray + "Update the index mapping using anArray as the new externalObjectsArray." + + externalObjectsArray := anArray. + freeSlotIndexes reset. + indexesByObjects removeAll. + 1 to: externalObjectsArray size do: [ :index | + (anArray at: index) + ifNil: [ freeSlotIndexes addFirst: index ] + ifNotNil: [ :object | indexesByObjects at: object put: index ] ]! Item was added: + ----- Method: ExternalObjectTable>>initialize (in category 'initialize-release') ----- + initialize + + semaphore := Semaphore forMutualExclusion. + self initializeCaches! Item was added: + ----- Method: ExternalObjectTable>>initializeCaches (in category 'private') ----- + initializeCaches + + freeSlotIndexes := OrderedCollection new. + indexesByObjects := IdentityDictionary new! Item was added: + ----- Method: ExternalObjectTable>>newExternalSemaphore (in category 'accessing') ----- + newExternalSemaphore + "Create and register a new Semaphore, and return an array containing itself and its index." + + | newSemaphore | + ^{ + newSemaphore := Semaphore new. + semaphore critical: [ + self + synchronizeExternalObjectsArrayAndForceUpdate: false; + safelyRegisterNewExternalObject: newSemaphore ] }! Item was added: + ----- Method: ExternalObjectTable>>newExternalSemaphoreDo: (in category 'accessing') ----- + newExternalSemaphoreDo: aBlock + "Create and register a new Semaphore, then evaluate aBlock with it and its index." + + | newSemaphore | + ^aBlock + value: (newSemaphore := Semaphore new) + value: (semaphore critical: [ + self + synchronizeExternalObjectsArrayAndForceUpdate: false; + safelyRegisterNewExternalObject: newSemaphore ])! Item was added: + ----- Method: ExternalObjectTable>>newExternalSemaphores: (in category 'accessing') ----- + newExternalSemaphores: count + "Create and register multiple Semaphores, and return an array containing the semaphores and their indexes in separate arrays." + + | semaphores indexes | + semaphores := Array new: count. + 1 to: count do: [ :index | semaphores at: index put: Semaphore new ]. + indexes := Array new: count. + semaphore critical: [ + self synchronizeExternalObjectsArrayAndForceUpdate: false. + 1 to: count do: [ :index | + indexes at: index put: ( + self safelyRegisterNewExternalObject: (semaphores at: index)) ] ]. + ^{ semaphores. indexes }! Item was added: + ----- Method: ExternalObjectTable>>registerExternalObject: (in category 'accessing') ----- + registerExternalObject: anObject + "Register the given object in the external objects array and return its index. If it is already there, just return its index." + + anObject ifNil: [ ^nil ]. + ^semaphore critical: [ + self + synchronizeExternalObjectsArrayAndForceUpdate: false; + safelyRegisterExternalObject: anObject ]! Item was added: + ----- Method: ExternalObjectTable>>safelyRegisterExternalObject: (in category 'private') ----- + safelyRegisterExternalObject: anObject + + | index | + (index := indexesByObjects at: anObject ifAbsent: nil) ifNotNil: [ + (externalObjectsArray at: index) == anObject ifTrue: [ ^index ]. + "indexesByObjects is out of sync. Try again." + ^self + synchronizeExternalObjectsArrayAndForceUpdate: true; + safelyRegisterExternalObject: anObject ]. + ^self safelyRegisterNewExternalObject: anObject! Item was added: + ----- Method: ExternalObjectTable>>safelyRegisterNewExternalObject: (in category 'private') ----- + safelyRegisterNewExternalObject: anObject + + | index | + self ensureFreeSlot. + index := freeSlotIndexes removeLast. + (externalObjectsArray at: index) ifNotNil: [ + "Free slot is not empty. Try again." + ^self + synchronizeExternalObjectsArrayAndForceUpdate: true; + safelyRegisterNewExternalObject: anObject ]. + externalObjectsArray at: index put: anObject. + indexesByObjects at: anObject put: index. + ^index! Item was added: + ----- Method: ExternalObjectTable>>safelyUnregisterExternalObject: (in category 'private') ----- + safelyUnregisterExternalObject: anObject + + (indexesByObjects removeKey: anObject ifAbsent: nil) + ifNotNil: [ :index | + (externalObjectsArray at: index) == anObject ifFalse: [ + "We're not in sync. Try again." + ^self + synchronizeExternalObjectsArrayAndForceUpdate: true; + safelyUnregisterExternalObject: anObject ]. + externalObjectsArray at: index put: nil. + freeSlotIndexes add: index ] + ifNil: [ + "Check if we're just out of sync." + (externalObjectsArray instVarsInclude: anObject) ifFalse: [ ^self ]. + "We're not in sync. Try again." + ^self + synchronizeExternalObjectsArrayAndForceUpdate: true; + safelyUnregisterExternalObject: anObject ]! Item was added: + ----- Method: ExternalObjectTable>>synchronizeExternalObjectsArrayAndForceUpdate: (in category 'private') ----- + synchronizeExternalObjectsArrayAndForceUpdate: forceUpdate + + | actualExternalObjectsArray | + actualExternalObjectsArray := Smalltalk specialObjectsArray at: 39. + (actualExternalObjectsArray == externalObjectsArray and: [ forceUpdate not ]) + ifTrue: [ ^self ]. + self externalObjectsArray: actualExternalObjectsArray! Item was added: + ----- Method: ExternalObjectTable>>unregisterExternalObject: (in category 'accessing') ----- + unregisterExternalObject: anObject + "Unregister the given object from the external objects array. Do nothing if it isn't registered." + + anObject ifNil: [ ^self ]. + semaphore critical: [ + self + synchronizeExternalObjectsArrayAndForceUpdate: false; + safelyUnregisterExternalObject: anObject ]! Item was added: + ----- Method: ExternalObjectTable>>unregisterExternalObjects: (in category 'accessing') ----- + unregisterExternalObjects: aCollection + "Unregister the given objects from the external objects array. Do nothing if they aren't registered." + + semaphore critical: [ + self synchronizeExternalObjectsArrayAndForceUpdate: false. + aCollection do: [ :each | + each ifNotNil: [ + self safelyUnregisterExternalObject: each ] ] ]! Item was removed: - Object subclass: #ExternalSemaphoreTable - instanceVariableNames: '' - classVariableNames: 'ProtectTable' - poolDictionaries: '' - category: 'System-Support'! - - !ExternalSemaphoreTable commentStamp: '<historical>' prior: 0! - By John M McIntosh johnmci(a)smalltalkconsulting.com - This class was written to mange the external semaphore table. When I was writing a Socket test server I discovered various race conditions on the access to the externalSemaphore table. This new class uses class side methods to restrict access using a mutex semaphore. It seemed cleaner to deligate the reponsibility here versus adding more code and another class variable to SystemDictionary - - Note that in Smalltalk recreateSpecialObjectsArray we still directly play with the table.! Item was removed: - ----- Method: ExternalSemaphoreTable class>>clearExternalObjects (in category 'accessing') ----- - clearExternalObjects - "Clear the array of objects that have been registered for use in non-Smalltalk code." - - ProtectTable critical: [Smalltalk specialObjectsArray at: 39 put: Array new]. - ! Item was removed: - ----- Method: ExternalSemaphoreTable class>>externalObjects (in category 'accessing') ----- - externalObjects - ^ProtectTable critical: [Smalltalk specialObjectsArray at: 39].! Item was removed: - ----- Method: ExternalSemaphoreTable class>>initialize (in category 'initialize') ----- - initialize - ProtectTable := Semaphore forMutualExclusion! Item was removed: - ----- Method: ExternalSemaphoreTable class>>registerExternalObject: (in category 'accessing') ----- - registerExternalObject: anObject - ^ ProtectTable critical: [self safelyRegisterExternalObject: anObject] - ! Item was removed: - ----- Method: ExternalSemaphoreTable class>>safelyRegisterExternalObject: (in category 'accessing') ----- - safelyRegisterExternalObject: anObject - "Register the given object in the external objects array and return its index. If it is already there, just return its index." - - | objects firstEmptyIndex obj sz newObjects | - objects := Smalltalk specialObjectsArray at: 39. - - "find the first empty slot" - firstEmptyIndex := 0. - 1 to: objects size do: [:i | - obj := objects at: i. - obj == anObject ifTrue: [^ i]. "object already there, just return its index" - (obj == nil and: [firstEmptyIndex = 0]) ifTrue: [firstEmptyIndex := i]]. - - "if no empty slots, expand the array" - firstEmptyIndex = 0 ifTrue: [ - sz := objects size. - newObjects := objects species new: sz + 20. "grow linearly" - newObjects replaceFrom: 1 to: sz with: objects startingAt: 1. - firstEmptyIndex := sz + 1. - Smalltalk specialObjectsArray at: 39 put: newObjects. - objects := newObjects]. - - objects at: firstEmptyIndex put: anObject. - ^ firstEmptyIndex - ! Item was removed: - ----- Method: ExternalSemaphoreTable class>>safelyUnregisterExternalObject: (in category 'accessing') ----- - safelyUnregisterExternalObject: anObject - "Unregister the given object in the external objects array. Do nothing if it isn't registered. - JMM change to return if we clear the element, since it should only appear once in the array" - - | objects | - anObject ifNil: [^ self]. - objects := Smalltalk specialObjectsArray at: 39. - 1 to: objects size do: [:i | - (objects at: i) == anObject ifTrue: - [objects at: i put: nil. - ^self]]. - ! Item was removed: - ----- Method: ExternalSemaphoreTable class>>unregisterExternalObject: (in category 'accessing') ----- - unregisterExternalObject: anObject - ProtectTable critical: [self safelyUnregisterExternalObject: anObject] - ! Item was changed: + ----- Method: SmalltalkImage>>clearExternalObjects (in category 'external objects') ----- - ----- Method: SmalltalkImage>>clearExternalObjects (in category 'special objects') ----- clearExternalObjects "Clear the array of objects that have been registered for use in non-Smalltalk code." "Smalltalk clearExternalObjects" + ExternalObjectTable current clearExternalObjects - ExternalSemaphoreTable clearExternalObjects ! Item was changed: + ----- Method: SmalltalkImage>>externalObjects (in category 'external objects') ----- - ----- Method: SmalltalkImage>>externalObjects (in category 'special objects') ----- externalObjects "Return an array of objects that have been registered for use in non-Smalltalk code. Smalltalk objects should be referrenced by external code only via indirection through this array, thus allowing the objects to move during compaction. This array can be cleared when the VM re-starts, since variables in external code do not survive snapshots. Note that external code should not attempt to access a Smalltalk object, even via this mechanism, while garbage collection is in progress." + "Note that this is just a copy of the array used by the VM." "Smalltalk externalObjects" + ^ExternalObjectTable current externalObjects - ^ ExternalSemaphoreTable externalObjects ! Item was added: + ----- Method: SmalltalkImage>>newExternalSemaphore (in category 'external objects') ----- + newExternalSemaphore + "Create and register a new Semaphore, and return an array containing itself and its index." + + ^ExternalObjectTable current newExternalSemaphore! Item was added: + ----- Method: SmalltalkImage>>newExternalSemaphoreDo: (in category 'external objects') ----- + newExternalSemaphoreDo: aBlock + "Create and register a new Semaphore, then evaluate aBlock with it and its index." + + ^ExternalObjectTable current newExternalSemaphoreDo: aBlock! Item was added: + ----- Method: SmalltalkImage>>newExternalSemaphores: (in category 'external objects') ----- + newExternalSemaphores: count + "Create and register multiple Semaphores, and return an array containing the semaphores and their indexes in separate arrays." + + ^ExternalObjectTable current newExternalSemaphores: count! Item was changed: + ----- Method: SmalltalkImage>>registerExternalObject: (in category 'external objects') ----- - ----- Method: SmalltalkImage>>registerExternalObject: (in category 'special objects') ----- registerExternalObject: anObject "Register the given object in the external objects array and return its index. If it is already there, just return its index." + ^ExternalObjectTable current registerExternalObject: anObject! - ^ExternalSemaphoreTable registerExternalObject: anObject! Item was changed: + ----- Method: SmalltalkImage>>unregisterExternalObject: (in category 'external objects') ----- - ----- Method: SmalltalkImage>>unregisterExternalObject: (in category 'special objects') ----- unregisterExternalObject: anObject "Unregister the given object in the external objects array. Do nothing if it isn't registered." + ExternalObjectTable current unregisterExternalObject: anObject! - ExternalSemaphoreTable unregisterExternalObject: anObject! Item was added: + ----- Method: SmalltalkImage>>unregisterExternalObjects: (in category 'external objects') ----- + unregisterExternalObjects: aCollection + "Unregister the given objects from the external objects array. Do nothing if they aren't registered." + + ExternalObjectTable current unregisterExternalObjects: aCollection!

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The Inbox: Sound-ul.41.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of Sound was added to project The Inbox: http://source.squeak.org/inbox/Sound-ul.41.mcz ==================== Summary ==================== Name: Sound-ul.41 Author: ul Time: 27 October 2014, 4:48:59.268 pm UUID: b700fc19-c219-47e3-bc55-4874db9dea22 Ancestors: Sound-nice.38 - use the new ExternalObjectTable API =============== Diff against Sound-nice.38 =============== Item was changed: ----- Method: SoundPlayer class>>startPlayerProcessBufferSize:rate:stereo:sound: (in category 'player process') ----- startPlayerProcessBufferSize: bufferSize rate: samplesPerSecond stereo: stereoFlag sound: aSound "Start the sound player process. Terminate the old process, if any." "SoundPlayer startPlayerProcessBufferSize: 1000 rate: 11025 stereo: false" self stopPlayerProcess. aSound ifNil:[ActiveSounds := OrderedCollection new] ifNotNil:[ActiveSounds := OrderedCollection with: aSound]. Buffer := SoundBuffer newStereoSampleCount: (bufferSize // 4) * 4. LastBuffer ifNotNil:[LastBuffer := SoundBuffer basicNew: Buffer basicSize]. PlayerSemaphore := Semaphore forMutualExclusion. SamplingRate := samplesPerSecond. Stereo := stereoFlag. - ReadyForBuffer := Semaphore new. SoundSupported := true. "Assume so" UseReadySemaphore := true. "set to false if ready semaphore not supported by VM" + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + ReadyForBuffer := semaphore. + self primSoundStartBufferSize: Buffer stereoSampleCount + rate: samplesPerSecond + stereo: Stereo + semaIndex: index ]. - self primSoundStartBufferSize: Buffer stereoSampleCount - rate: samplesPerSecond - stereo: Stereo - semaIndex: (Smalltalk registerExternalObject: ReadyForBuffer). "Check if sound start prim was successful" + SoundSupported ifFalse:[ + Smalltalk unregisterExternalObject: ReadyForBuffer. + ReadyForBuffer := nil. + ^self ]. - SoundSupported ifFalse:[^self]. UseReadySemaphore ifTrue: [PlayerProcess := [SoundPlayer playLoop] newProcess] ifFalse: [PlayerProcess := [SoundPlayer oldStylePlayLoop] newProcess]. UseReverb ifTrue: [self startReverb]. PlayerProcess priority: Processor userInterruptPriority. + PlayerProcess resume! - PlayerProcess resume.! Item was changed: ----- Method: SoundRecorder>>startRecording (in category 'recording controls') ----- startRecording "Turn of the sound input driver and start the recording process. Initially, recording is paused." - | semaIndex | recordLevel ifNil: [recordLevel := 0.5]. "lazy initialization" CanRecordWhilePlaying ifFalse: [SoundPlayer shutDown]. recordProcess ifNotNil: [self stopRecording]. paused := true. meteringBuffer := SoundBuffer newMonoSampleCount: 1024. meterLevel := 0. self allocateBuffer. + Smalltalk newExternalSemaphoreDo: [ :semaphore :index | + bufferAvailableSema := semaphore. + self primStartRecordingDesiredSampleRate: samplingRate asInteger + stereo: stereo + semaIndex: index ]. - bufferAvailableSema := Semaphore new. - semaIndex := Smalltalk registerExternalObject: bufferAvailableSema. - self primStartRecordingDesiredSampleRate: samplingRate asInteger - stereo: stereo - semaIndex: semaIndex. RecorderActive := true. samplingRate := self primGetActualRecordingSampleRate. self primSetRecordLevel: (1000.0 * recordLevel) asInteger. recordProcess := [self recordLoop] newProcess. recordProcess priority: Processor userInterruptPriority. + recordProcess resume! - recordProcess resume. - !

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The Inbox: Universes-kfr.47.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of Universes was added to project The Inbox: http://source.squeak.org/inbox/Universes-kfr.47.mcz ==================== Summary ==================== Name: Universes-kfr.47 Author: kfr Time: 27 October 2014, 2:01:04.363 pm UUID: be75a4ac-e8b3-834d-af8f-23cf47fcac79 Ancestors: Universes-nice.46 Remove entries in world menu =============== Diff against Universes-nice.46 =============== Item was changed: ----- Method: UUniverseBrowser class>>unload (in category 'class initialization') ----- unload + #('Package Universe Browser' 'Universe Browser (basic)') do: [:oldName | + TheWorldMenu unregisterOpenCommand: oldName ].! - TheWorldMenu unregisterOpenCommand: 'Universe Browser (basic)'!

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New Cog VMs available
by Eliot Miranda 27 Oct '14

27 Oct '14

...at http://www.mirandabanda.org/files/Cog/VM/VM.r3114/. CogVM binaries as per VMMaker.oscog-eem.913/r3114 Spur: Fix baaaad bug in checking for still-married contexts in Spur. One *cannot* simply follow what is assumed to be the frameContext field of what is presumed to be a context. On Spur we need to *know* whether we have a valid frameContext field, and for that we have to know there is a valid frame. So refactor, moving isFrame:onPage: from StackInterpreterPrimitives to StackInterpreter, and use it to validate the frame pointer of a maybe married context before testing the context for being forwarded. All: Avoid cogging methods containing unknown bytecodes early in scanMethod. Use a hack to avoid a test on the common path. Fix assert fail cases in ceInterpretMethodFromPIC:receiver: Both of these together fix assert fails due to cogging methods containing unknown bytecodes. Spur: Implement image segments. Use Igor's idea of splitting the computation of the transitive closure from the writing of the image segment for simplicity, even if the two are together into a single primitive for backwards-compatibility. All: Rewrite the two image segment primitives to pass back an error code on failure, and rewrite the (New)ObjectMemory code to answer informative failure codes. Print slots of word objects in longPrintOop: Fix parenthesization bugs in validation code in some Alien plugin primtiives. Make findClassContainingMethod:startingAt: et al robust in the face of faulted-out classes (nil method dictionaries). Include the AioPlugin in the Newspeak linux VMs; recent reports indicate it's essential to good performance in recent versions of OSProcessPlugin. Unix startup script: Quote the LD_LIBRARY_PATH setting to tolerate directory names with spaces. -- best, Eliot

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Daily Commit Log
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

Changes to Trunk (http://source.squeak.org/trunk.html) in the last 24 hours: http://lists.squeakfoundation.org/pipermail/packages/2014-October/007346.ht… Name: Monticello-mtf.603 Ancestors: Monticello-ul.602 Print the right thing for class-side traits =============================================

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The Inbox: Collections-ul.586.mcz
by commits＠source.squeak.org 27 Oct '14

27 Oct '14

A new version of Collections was added to project The Inbox: http://source.squeak.org/inbox/Collections-ul.586.mcz ==================== Summary ==================== Name: Collections-ul.586 Author: ul Time: 27 October 2014, 12:52:51.886 am UUID: 4c460675-3065-4b48-aa30-52ad67e15076 Ancestors: Collections-cmm.585 Symbol table changes: - ensure that enumerations stay consistent - avoid read-write and write-write race conditions - added a safe #condenseNewSymbols method, which is a replacement for former unsafe methods (#shutDown: and #compactSymbolTable). It's also automatically triggered whenever there are more than 1000 NewSymbols. - deprecated #compactSymbolTable - updated some comments Note that interning many symbols is a bit slower, but thread safety is more important. =============== Diff against Collections-cmm.585 =============== Item was changed: ----- Method: Symbol class>>allSymbolTablesDo: (in category 'class initialization') ----- allSymbolTablesDo: aBlock + + | originalNewSymbols originalSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. + originalNewSymbols do: aBlock. + originalSymbolTable do: aBlock.! - - NewSymbols do: aBlock. - SymbolTable do: aBlock.! Item was changed: ----- Method: Symbol class>>allSymbolTablesDo:after: (in category 'class initialization') ----- allSymbolTablesDo: aBlock after: aSymbol + | originalNewSymbols originalSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. + (originalNewSymbols includes: aSymbol) - (NewSymbols includes: aSymbol) ifTrue: [ + originalNewSymbols do: aBlock after: aSymbol. + originalSymbolTable do: aBlock after: aSymbol ] - NewSymbols do: aBlock after: aSymbol. - SymbolTable do: aBlock after: aSymbol ] ifFalse: [ + originalSymbolTable do: aBlock after: aSymbol. + originalNewSymbols do: aBlock after: aSymbol ] - SymbolTable do: aBlock after: aSymbol. - NewSymbols do: aBlock after: aSymbol ] ! Item was changed: ----- Method: Symbol class>>allSymbols (in category 'access') ----- allSymbols "Answer all interned symbols" + | originalNewSymbols originalSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. ^Array + new: originalNewSymbols slowSize + originalSymbolTable slowSize - new: NewSymbols slowSize + SymbolTable slowSize streamContents:[ :stream | stream + nextPutAll: originalNewSymbols; + nextPutAll: originalSymbolTable ] - nextPutAll: NewSymbols; - nextPutAll: SymbolTable ] ! Item was changed: ----- Method: Symbol class>>cleanUp (in category 'class initialization') ----- cleanUp "Flush caches" + self condenseNewSymbols! - self compactSymbolTable.! Item was changed: ----- Method: Symbol class>>compactSymbolTable (in category 'class initialization') ----- compactSymbolTable "Reduce the size of the symbol table so that it holds all existing symbols with 25% free space." + self deprecated: 'Use #condenseNewSymbols instead'. + self condenseNewSymbols! - | oldSize | - Smalltalk garbageCollect. - oldSize := SymbolTable capacity. - SymbolTable compact. - ^(oldSize - SymbolTable capacity) printString, ' slot(s) reclaimed'! Item was added: + ----- Method: Symbol class>>condenseNewSymbols (in category 'private') ----- + condenseNewSymbols + "Move all symbols from NewSymbols to SymbolTable, and compact SymbolTable." + + | originalNewSymbols originalSymbolTable newNewSymbols newSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. + newNewSymbols := WeakSet new. + newSymbolTable := originalSymbolTable copy + addAll: originalNewSymbols; + compact; + yourself. + originalNewSymbols == NewSymbols ifFalse: [ + "Some other process has modified the symbols. Try again." + ^self condenseNewSymbols ]. + NewSymbols := newNewSymbols. + SymbolTable := newSymbolTable! Item was changed: ----- Method: Symbol class>>intern: (in category 'instance creation') ----- intern: aStringOrSymbol + | originalNewSymbols | + originalNewSymbols := NewSymbols. ^(self lookup: aStringOrSymbol) ifNil:[ + | aClass aSymbol newNewSymbols | - | aClass aSymbol | aStringOrSymbol isSymbol ifTrue:[ aSymbol := aStringOrSymbol. ] ifFalse:[ aClass := aStringOrSymbol isOctetString ifTrue:[ByteSymbol] ifFalse:[WideSymbol]. aSymbol := aClass new: aStringOrSymbol size. aSymbol string: aStringOrSymbol. ]. + newNewSymbols := originalNewSymbols copyWith: aSymbol. + originalNewSymbols == NewSymbols + ifTrue: [ + NewSymbols := newNewSymbols. + newNewSymbols size > 1000 ifTrue: [ self condenseNewSymbols ]. + aSymbol ] + ifFalse: [ + "Some other process has modified the symbols. Try again." + self intern: aStringOrSymbol ] ]! - NewSymbols add: aSymbol. - aSymbol].! Item was changed: ----- Method: Symbol class>>lookup: (in category 'instance creation') ----- lookup: aStringOrSymbol + | originalNewSymbols originalSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. + ^(originalNewSymbols like: aStringOrSymbol) ifNil: [ + originalSymbolTable like: aStringOrSymbol ]! - ^(SymbolTable like: aStringOrSymbol) ifNil: [ - NewSymbols like: aStringOrSymbol - ]! Item was changed: ----- Method: Symbol class>>rehash (in category 'private') ----- + rehash + "Rebuild the hash table, reclaiming unreferenced Symbols. This method will intern all symbols. You're probably looking for #condenseNewSymbols instead." - rehash "Symbol rehash" - "Rebuild the hash table, reclaiming unreferenced Symbols." + | originalNewSymbols originalSymbolTable newNewSymbols newSymbolTable | + originalNewSymbols := NewSymbols. + originalSymbolTable := SymbolTable. + newNewSymbols := WeakSet new. + newSymbolTable := WeakSet withAll: self allSubInstances. + originalNewSymbols == NewSymbols ifFalse: [ + "Some other process has modified the symbols. Try again." + ^self rehash ]. + NewSymbols := newNewSymbols. + SymbolTable := newSymbolTable! - SymbolTable := WeakSet withAll: self allSubInstances. - NewSymbols := WeakSet new.! Item was changed: ----- Method: Symbol class>>shutDown: (in category 'private') ----- shutDown: aboutToQuit + self condenseNewSymbols! - SymbolTable addAll: NewSymbols. - NewSymbols := WeakSet new.!

1 0

New Spur trunk image available
by Eliot Miranda 26 Oct '14

26 Oct '14

Hi All, finally the Spur Squeak trunk image is updateable. The image in http://www.mirandabanda.org/files/Cog/SpurImages/2014-10-16/ was created today and thanks to Bert Freudenberg's latest Monticello work can be updated independently of the non-Spur trunk. Spur VMs are available in http://www.mirandabanda.org/files/Cog/VM/VM.r3105/ (and later as they appear). Without wanting to appear too overconfident the Spur system looks to be ready for use apart from image segments (which I hope to have working some time next month). I'm really interested in having this stress tested by as many people as possible. Spur really does offer a significant performance and functionality improvement over the current system, but it needs testing to ensure its reliability. Esteban Lorenzano is hard at work on the Pharo bootstrap for Spur so I hope Pharo 4 Spur will be available soon. As far as trunk goes, using Spur alongside non-Spur trunk is going to be difficult to manage for the near future. Right now, Spur modifies the Collections, Compiler, Kernel and System packages, and this is done by auto-editing the non-Spur versions of those packages, something I do periodically as new versions arrive. I also auto-edit trunk configurations (the part of the image update scheme that ensures packages are loaded in the right order when there are dependencies between packages) from non-Spur "update" to Spur "update.spur" forms. This at east means that Spur can keep up with trunk. But it does /not/ provide a way of committing to Collections.spur, Compiler.spur, Kernel.spur or System.spur without getting out of sync with non-Spur trunk. Note that apart from these packages, one /can/ safely commit any other package from a Spur image to trunk. Right now the plan is to release both V3 (the pre-Spur format) and Spur versions of Squeak 4.6 (I hope it'll be called Squeak 5.0). This isn't my preference. I'd like to see just Spur released, once reliability is verified. But I understand the safety and backward-compatibility concerns (Spur won't be able to load V3 image segments, and vice verse). The issue is of course that we have this tricky package situation to manage where, to keep the two systems in sync, modifications to Collections, Compiler, Kernel and System need to be committed from V3 and auto-edited to Spur. I think that's too clumsy to be practicable. Perhaps allowing the two systems to fork and doing a manual merge will be acceptable, but it'll be work to keep them in sync. -- best, Eliot

8 12

Image Segment semantics and weakness
by Eliot Miranda 26 Oct '14

26 Oct '14

Hi All, I want to check my understanding of reference semantics for image segments as I'm close to completing the Spur implementation. Specifically the question is whether objects reachable only through weak pointers should be included in an image segment or not. Remember that an image segment is created from the transitive closure of an Array of root objects, the *segment roots*. i.e. we can think of an image segment as a set of objects created by tracing the object graph from the segment roots. The segment always includes the segment roots. Except for the roots, objects are excluded from the segment that are also reachable form the roots of the system (the *system roots*, effectively the root environment, Smalltalk, and the stack of the current process). Consider a weak array in the transitive closure that is not reachable from the system roots, and hence should be included in the segment. Objects referenced from that weak array may be in one of three categories - reachable from the system roots (and hence not to be included in the segment) - *not* reachable form the system roots, but reachable from the segment roots via strong pointers (and hence to be included in the segment) - *not* reachable form the system roots, *not* reachable from the segment roots via strong pointers Should this last category be included or excluded from the segment? I think that it makes no difference, and excluding them is only an optimization. The argument is as follows. Imagine that immediately after loading the image segment there is a garbage collection. That garbage collection will collect all the objects in the last category as they are only reachable from the weak arrays in the segment. Hence we are free to follow weak references as if they are strong when we create the image segment, leaving it to subsequent events to reclaim those objects. An analogous argument accounts for objects reachable from ephemerons. Is my reasoning sound? -- best, Eliot

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