I introduced the method #supportsWriteBarrier in Pharo 6. You can backport it if you want:
VirtualMachine>>#supportsWriteBarrier "Answer whether the VM observes the per-object read-only flag and consequently aborts writes to inst vars of, and fails primitives that attempt to write, to read-only objects." ^(self parameterAt: 65) ifNil: [false] ifNotNil: [:param| "In older VMs this is a boolean reflecting MULTIPLE_BYTECODE_SETS" param isInteger "In newer VMs it is a set of integer flags, bit 1 of which is IMMUTABILITY" ifTrue: [param anyMask: 2] ifFalse: [false]] On Wed, Jan 25, 2017 at 2:06 PM, p...@highoctane.be <p...@highoctane.be> wrote: > The "latest" Windows VM I do use has no such method. > > Virtual Machine > --------------- > C:\Users\Philippe\Dropbox\Sibelga\JiraAutomation\Pharo5. > 0\latestvm\pharo.exe > CoInterpreter * VMMaker.oscog-eem.2090 uuid: > 63a161b9-17e1-4911-a89a-1687d9ba9a1a > Jan 15 2017 > StackToRegisterMappingCogit * VMMaker.oscog-eem.2090 uuid: > 63a161b9-17e1-4911-a89a-1687d9ba9a1a Jan 15 2017 > VM: 201701151442 https://github.com/pharo-project/pharo-vm.git $ Date: > Sun Jan 15 15:42:39 2017 +0100 $ Plugins: 201701151442 > https://github.com/pharo-project/pharo-vm.git $ > > Win32 built on Jan 15 2017 15:59:52 CUT Compiler: 5.4.0 > VMMaker versionString VM: 201701151442 https://github.com/pharo- > project/pharo-vm.git $ Date: Sun Jan 15 15:42:39 2017 +0100 $ Plugins: > 201701151442 https://github.com/pharo-project/pharo-vm.git $ > CoInterpreter * VMMaker.oscog-eem.2090 uuid: > 63a161b9-17e1-4911-a89a-1687d9ba9a1a > Jan 15 2017 > StackToRegisterMappingCogit * VMMaker.oscog-eem.2090 uuid: > 63a161b9-17e1-4911-a89a-1687d9ba9a1a Jan 15 2017 > > [image: Inline image 1] > > > On Wed, Jan 25, 2017 at 1:54 PM, Clément Bera <bera.clem...@gmail.com> > wrote: > >> >> >> On Wed, Jan 25, 2017 at 11:35 AM, Norbert Hartl <norb...@hartl.name> >> wrote: >> >>> Does anyone know the state of immutability support in vm and image? The >>> latest vm downloadable is compiled with >>> >>> IMMUTABILITY=1 >>> >>> (Esteban said that). When I open a pharo6 image with this VM and do: >>> >>> ASUser new >>> setIsReadOnlyObject: true; >>> name: 'foo' >>> >>> with >>> >>> ASUser>>#name: arg1 >>> name := arg1 >>> >>> I don't get an exception. Is there something missing or am I not >>> understanding? >>> >> >> Hi Norbert, >> >> Thank you very much for looking read-only objects. >> >> When mutating an instance variable, the VM triggers a call-back that by >> default does nothing. In your case, running your code does not raise an >> exception but the object should not be modified either. If you want an >> exception, you need to change the call-back code, i.e., the method >> Object>>#attemptToAssign: value withIndex: index. For example, you could >> write: >> >> Object>>#attemptToAssign: value withIndex: index >> | process | >> self notify: 'object changed !'. >> process := Processor activeProcess. >> [ process suspendedContext: process suspendedContext sender ] forkAt: >> Processor activePriority + 1. >> Processor yield. >> >> Then, your code should open a notification window with 'object changed', >> and proceeding keeps running the code without mutating the object. >> >> One needs to build a ModificationTracker framework on top of the VM >> support I introduced. Multiple things are required, like default behavior >> in this call-back and in primitive failure code. I am willing to support >> and help anyone willing to build such a framework, but I won't build it >> myself. >> >> If you have any other questions or if you find bug don't hesitate to ask >> further questions >> >> Best, >> >> PS: Make sure "Smalltalk vm supportsWriteBarrier" answers true in your >> system, if this is not the case it means the VM does not support read-only >> objects. >> >> Clement >> >> >> >> >> >> >>> >>> Norbert >>> >> >> >
