Feel free to improve the code.  I merely adapted the Pharo changes to 
Cuis.  I am not really aware of your long term plans.  Please let me 
know what you decide to do in the end, as I'd like to keep Cuis in the loop.

On 9/12/14 17:14 , Eliot Miranda wrote:
>
>
> On Fri, Sep 12, 2014 at 2:12 PM, Frank Shearar <frank.shearar at gmail.com
> <mailto:frank.shearar at gmail.com>> wrote:
>
>     On 12 September 2014 21:49, Eliot Miranda <eliot.miranda at gmail.com
>     <mailto:eliot.miranda at gmail.com>> wrote:
>     > Hi Frank,
>     >
>     >     I'd rather see
>     >
>     > on: exception do: handlerAction
>     >        "Evaluate the receiver in the scope of an exception handler.
>     >        The following primitive is just a marker used to find the error
>     > handling context.
>     >        See MethodContext>>#isHandlerOrSignalingContext. "
>     >        <primitive: 199>
>     >        <handler>
>     >        ^ self value!
>     >
>     > isHandlerContext
>     >        "is this context for #on:do:?"
>     >        ^self isHandlerOrSignalingContext and: [ (self method pragmaAt:
>     > #handler) notNil: ]
>     >
>     > etc, rather than testing the selector.
>
>     OK, I see what you're doing there. I guess the only worry I have is
>     that <handler> doesn't seem terribly specific to me.
>
>
> it can be as specific a label as you'd like.
>
>
>     One thing I don't get is the tempAt: 3 stuff. This code removes it,
>     and that seems to be the root of why #testHandlerReentrancy fails. But
>     this is beyond my depth (which is most of why I made Andres' code more
>     available for those for home this is _not_ out of depth).
>
>
> I hear you.
>
>     >  I'd also like to see the code in
>     > MethodCOntext (e.g. where method can be directly accessed) than in
>     > ContextPart.  Remember that some time soon we can collapse ContextPart and
>     > MethodContext onto Context as the Pharo folks have already done.
>
>     Right, because BlockContext has been marked for death? (Because
>     MethodContext has a closureOrNil instvar, which disambiguates between
>     MethodContexts-for-block-activations and
>     MethodContexts-for-method-activations.)
>
>
> Right.  BlockCOntext is obsolete and unused.
>
>     But since at some point we're going to merge MethodContext and
>     ContextPart, why not just leave the code where it is? I guess it just
>     depends on whether we merge MethodContext -> ContextPart, or
>     ContextPart -> MethodContext.
>
>
> Well, the inst vars contexts need are defined in InstructionStream and
> MethodContext. So implementing in MethodCOntext allows e.g. direct
> access to method.  So I don't recommend putting things in ContextPart
> any more.
>
>
>     frank
>
>      > On Fri, Sep 12, 2014 at 1:40 PM, <commits at source.squeak.org
>     <mailto:commits at source.squeak.org>> wrote:
>      >>
>      >> Frank Shearar uploaded a new version of Kernel to project The Inbox:
>      >> http://source.squeak.org/inbox/Kernel-fbs.870.mcz
>      >>
>      >> ==================== Summary ====================
>      >>
>      >> Name: Kernel-fbs.870
>      >> Author: fbs
>      >> Time: 12 September 2014, 9:40:45.406 pm
>      >> UUID: 868e0d8a-5e9d-d34d-ba2d-688800331f5b
>      >> Ancestors: Kernel-eem.869
>      >>
>      >> These are the changes Andres Valloud made to Cuis, to address a
>      >> long-standing bug in Cuis, Squeak and Pharo, in ExceptionsTests >>
>      >> #testHandlerFromAction.
>      >>
>      >> However, it causes a regression in #testHandlerReentrancy, so as
>     it stands
>      >> it is NOT READY FOR MERGING.
>      >>
>      >> Please take a look, and see if we can bend Andres' code slightly
>     so that
>      >> we get both the fix and don't break anything.
>      >>
>      >> =============== Diff against Kernel-eem.869 ===============
>      >>
>      >> Item was changed:
>      >>   ----- Method: BlockClosure>>on:do: (in category 'exceptions')
>     -----
>      >>   on: exception do: handlerAction
>      >> +       "Evaluate the receiver in the scope of an exception handler.
>      >> +       The following primitive is just a marker used to find
>     the error
>      >> handling context.
>      >> +       See MethodContext>>#isHandlerOrSignalingContext. "
>      >> +       <primitive: 199>
>      >> -       "Evaluate the receiver in the scope of an exception
>     handler."
>      >> -
>      >> -       | handlerActive |
>      >> -       <primitive: 199>  "just a marker, fail and execute the
>     following"
>      >> -       handlerActive := true.
>      >>         ^ self value!
>      >>
>      >> Item was changed:
>      >>   ----- Method: BlockContext>>on:do: (in category 'exceptions')
>     -----
>      >>   on: exception do: handlerAction
>      >> +       "Evaluate the receiver in the scope of an exception handler.
>      >> +       The following primitive is just a marker used to find
>     the error
>      >> handling context.
>      >> +       See MethodContext>>#isHandlerOrSignalingContext. "
>      >> +       <primitive: 199>
>      >> +       ^ self value!
>      >> -       "Evaluate the receiver in the scope of an exception
>     handler."
>      >> -       | handlerActive |
>      >> -       <primitive: 199>
>      >> -       handlerActive := true.
>      >> -       ^self value!
>      >>
>      >> Item was changed:
>      >>   ----- Method: ContextPart>>canHandleSignal: (in category
>      >> 'private-exceptions') -----
>      >>   canHandleSignal: exception
>      >>         "Sent to handler (on:do:) contexts only.  If my
>     exception class
>      >> (first arg) handles exception then return true, otherwise
>     forward this
>      >> message to the next handler context.  If none left, return false
>     (see
>      >> nil>>canHandleSignal:)"
>      >>
>      >> +       ^ (self exceptionClass handles: exception)
>      >> +               or: [ self nextHandlerContext canHandleSignal:
>     exception
>      >> ].!
>      >> -       ^ (((self tempAt: 1) handles: exception) and: [self
>     tempAt: 3])
>      >> -               or: [self nextHandlerContext canHandleSignal:
>     exception].
>      >> - !
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>evaluateSignal: (in category
>      >> 'private-exceptions') -----
>      >> + evaluateSignal: exception
>      >> +       "The following primitive is just a marker used to find the
>      >> evaluation context.
>      >> +       See MethodContext>>#isHandlerOrSignalingContext. "
>      >> +
>      >> +       <primitive: 199>
>      >> +       | value |
>      >> +       exception privHandlerContext: self contextTag.
>      >> +       value := self exceptionHandlerBlock
>     valueWithPossibleArgument:
>      >> exception.
>      >> +       "return from self if not otherwise directed in handle block"
>      >> +       self return: value!
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>exceptionClass (in category
>      >> 'private-exceptions') -----
>      >> + exceptionClass
>      >> +
>      >> +       ^self tempAt: 1!
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>exceptionHandlerBlock (in category
>      >> 'private-exceptions') -----
>      >> + exceptionHandlerBlock
>      >> +       "handler context only. access temporaries from
>      >> BlockClosure>>#on:do:"
>      >> +
>      >> +       ^self tempAt: 2!
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>findNextHandlerContext (in category
>      >> 'private-exceptions') -----
>      >> + findNextHandlerContext
>      >> +       "Return the next handler marked context, returning nil
>     if there is
>      >> none.  Search starts with self and proceeds up to nil."
>      >> +
>      >> +       | context |
>      >> +       context := self findNextHandlerOrSignalingContext.
>      >> +       context isNil
>      >> +               ifTrue: [ ^ nil ].
>      >> +       context isHandlerContext
>      >> +               ifTrue: [ ^ context ].  "If it isn't a handler
>     context, it
>      >> must be a signaling context.
>      >> +       When we reach a signaling context we must skip over any
>     handlers
>      >> +       that might be on the stack between the signaling context
>     and the
>      >> handler
>      >> +       context for that signal."
>      >> +       ^ context exceptionClass privHandlerContext
>     nextHandlerContext!
>      >>
>      >> Item was removed:
>      >> - ----- Method: ContextPart>>findNextHandlerContextStarting (in
>     category
>      >> 'private-exceptions') -----
>      >> - findNextHandlerContextStarting
>      >> -       "Return the next handler marked context, returning nil
>     if there is
>      >> none.  Search starts with self and proceeds up to nil."
>      >> -
>      >> -       | ctx |
>      >> -       <primitive: 197>
>      >> -       ctx := self.
>      >> -               [ctx isHandlerContext ifTrue:[^ctx].
>      >> -               (ctx := ctx sender) == nil ] whileFalse.
>      >> -       ^nil!
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>findNextHandlerOrSignalingContext (in
>      >> category 'private-exceptions') -----
>      >> + findNextHandlerOrSignalingContext
>      >> +       "Return the next handler/signaling marked context,
>     answering nil
>      >> if there is none.
>      >> +       Search starts with self and proceeds up to nil."
>      >> +
>      >> +       <primitive: 197>
>      >> +       | context |
>      >> +       context := self.
>      >> +       [
>      >> +       context isHandlerOrSignalingContext
>      >> +               ifTrue: [ ^ context ].
>      >> +       (context := context sender) == nil ] whileFalse.
>      >> +       ^ nil!
>      >>
>      >> Item was changed:
>      >>   ----- Method: ContextPart>>handleSignal: (in category
>      >> 'private-exceptions') -----
>      >>   handleSignal: exception
>      >>         "Sent to handler (on:do:) contexts only.  If my
>     exception class
>      >> (first arg) handles exception then execute my handle block
>     (second arg),
>      >> otherwise forward this message to the next handler context.  If
>     none left,
>      >> execute exception's defaultAction (see nil>>handleSignal:)."
>      >>
>      >> +       (self exceptionClass handles: exception)
>      >> +               ifFalse: [ ^ self nextHandlerContext handleSignal:
>      >> exception ].
>      >> +       self evaluateSignal: exception!
>      >> -       | val |
>      >> -       (((self tempAt: 1) handles: exception) and: [self
>     tempAt: 3])
>      >> ifFalse: [
>      >> -               ^ self nextHandlerContext handleSignal: exception].
>      >> -
>      >> -       exception privHandlerContext: self contextTag.
>      >> -       self tempAt: 3 put: false.  "disable self while
>     executing handle
>      >> block"
>      >> -       val := [(self tempAt: 2) cull: exception ]
>      >> -               ensure: [self tempAt: 3 put: true].
>      >> -       self return: val.  "return from self if not otherwise
>     directed in
>      >> handle block"
>      >> - !
>      >>
>      >> Item was changed:
>      >>   ----- Method: ContextPart>>isHandlerContext (in category
>      >> 'private-exceptions') -----
>      >>   isHandlerContext
>      >> +       "is this context for #on:do:?"
>      >> +       ^self isHandlerOrSignalingContext and: [ self selector
>     == #on:do:
>      >> ]!
>      >> -       ^false!
>      >>
>      >> Item was added:
>      >> + ----- Method: ContextPart>>isHandlerOrSignalingContext (in
>     category
>      >> 'private-exceptions') -----
>      >> + isHandlerOrSignalingContext
>      >> +       "Both BlockClosure>>on:do: (handler) and
>      >> ContextPart>>evaluateSignal: (signaling)
>      >> +       are marked with primitive 199."
>      >> +
>      >> +       ^false!
>      >>
>      >> Item was changed:
>      >>   ----- Method: ContextPart>>nextHandlerContext (in category
>      >> 'private-exceptions') -----
>      >>   nextHandlerContext
>      >>
>      >> +       ^ self sender findNextHandlerContext!
>      >> -       ^ self sender findNextHandlerContextStarting!
>      >>
>      >> Item was removed:
>      >> - ----- Method: ContextPart>>rearmHandlerDuring: (in category
>      >> 'private-exceptions') -----
>      >> - rearmHandlerDuring: aBlock
>      >> -       "Sent to handler (on:do:) contexts only. Makes me
>     re-entrant for
>      >> the duration of aBlock. Only works in a closure-enabled image"
>      >> -
>      >> -       ^ [self tempAt: 3 put: true. aBlock value]
>      >> -               ensure: [self tempAt: 3 put: false]!
>      >>
>      >> Item was added:
>      >> + ----- Method: Exception>>privHandlerContext (in category 'priv
>      >> handling') -----
>      >> + privHandlerContext
>      >> +
>      >> +       ^handlerContext!
>      >>
>      >> Item was removed:
>      >> - ----- Method: Exception>>rearmHandlerDuring: (in category
>     'handling')
>      >> -----
>      >> - rearmHandlerDuring: aBlock
>      >> - "Make the current error handler re-entrant while it is running
>     aBlock.
>      >> Only works in a closure-enabled image"
>      >> -
>      >> -       ^ handlerContext rearmHandlerDuring: aBlock!
>      >>
>      >> Item was removed:
>      >> - ----- Method: MethodContext>>isHandlerContext (in category
>      >> 'private-exceptions') -----
>      >> - isHandlerContext
>      >> - "is this context for  method that is marked?"
>      >> -       ^method primitive = 199!
>      >>
>      >> Item was added:
>      >> + ----- Method: MethodContext>>isHandlerOrSignalingContext (in
>     category
>      >> 'private-exceptions') -----
>      >> + isHandlerOrSignalingContext
>      >> +       "Both BlockClosure>>on:do: (handler) and
>      >> ContextPart>>evaluateSignal: (signaling)
>      >> +       are marked with primitive 199."
>      >> +
>      >> +       ^method primitive = 199!
>      >>
>      >>
>      >
>      >
>      >
>      > --
>      > best,
>      > Eliot
>      >
>      >
>      >
>
>
>
>
> --
> best,
> Eliot
>
>
>