The Inbox: Kernel-nice.1391.mcz

>
> Nicolas Cellier uploaded a new version of Kernel to project The Inbox:
> http://source.squeak.org/inbox/Kernel-nice.1391.mcz
>
> ==================== Summary ====================
>
> Name: Kernel-nice.1391
> Author: nice
> Time: 23 April 2021, 10:58:48.925778 am
> UUID: bde1d6d3-e3ba-48ad-b432-3ac5a1531880
> Ancestors: Kernel-nice.1390
>
> Remove the questionable ifCurtailed: block that did reactivate the handler in handleSignal:, and make the handling symetric, whether the handlerAction explicitily use exception return or not.
>
> Document the mysterious tempAt:/tempAt:put: intention by using proper method names as requested by Marcel.
> The slowdown shall be marginal, and system understanding should be improved.
>
> Provide messages to selectively reactivate some handler contexts. For gurus: handle with care!
>
> =============== Diff against Kernel-nice.1390 ===============
>
> Item was changed:
>   ----- Method: Context>>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 willHandleSignal: exception)
> -       ^ (((self tempAt: 1) handles: exception) and: [self tempAt: 3])
>                 or: [self nextHandlerContext canHandleSignal: exception].
>   !
>
> Item was added:
> + ----- Method: Context>>deactivateHandler (in category 'private-exceptions') -----
> + deactivateHandler
> +       "Private - sent to exception handler context only (on:do:)"
> +
> +       stackp >= 3 ifTrue: [self tempAt: 3 put: false] "this is temporary handlerActive in #on:do:"!
>
> Item was added:
> + ----- Method: Context>>fireHandlerActionWith: (in category 'private-exceptions') -----
> + fireHandlerActionWith: exception
> +       "Sent to handler (on:do:) contexts only.
> +       Perform the second argument, which is the handler action"
> +
> +       ^(self tempAt: 2) cull: exception!
>
> Item was changed:
>   ----- Method: Context>>handleSignal: (in category 'private-exceptions') -----
>   handleSignal: exception
>         "Sent to handler (on:do:) contexts only.  If my exception class (first arg) handles exception
>          and the handler is active 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:)."
>
> +       | val |
> +       (self willHandleSignal: exception) ifFalse:
> +               [self deactivateHandler.
> -       | handlerActive val |
> -       "If the context has been returned from the handlerActive temp var may not be accessible."
> -       handlerActive := stackp >= 3 and: [(self tempAt: 3) == true].
> -       (((self tempAt: 1) handles: exception) and: [handlerActive]) ifFalse:
> -               [stackp >= 3 ifTrue: [self tempAt: 3 put: false].
>                 ^self nextHandlerContext handleSignal: exception].
>
>         exception privHandlerContext: self contextTag.
> +       self deactivateHandler.  "disable self while executing handle block"
> +       val := self fireHandlerActionWith: exception.
> -       self tempAt: 3 put: false.  "disable self while executing handle block"
> -       val := [(self tempAt: 2) cull: exception]
> -                       ifCurtailed: [self tempAt: 3 put: true].
>         self return: val  "return from self if not otherwise directed in handle block"
>   !
>
> Item was added:
> + ----- Method: Context>>isHandlerActive (in category 'private-exceptions') -----
> + isHandlerActive
> +       "Private - sent to exception handler context only (on:do:)"
> +
> +       ^stackp >= 3 and: [(self tempAt: 3) == true] "this is temporary handlerActive in #on:do:"!
>
> Item was added:
> + ----- Method: Context>>reactivateHandler (in category 'private-exceptions') -----
> + reactivateHandler
> +       "Private - sent to exception handler context only (on:do:)"
> +
> +       stackp >= 3 ifTrue: [self tempAt: 3 put: true] "this is temporary handlerActive in #on:do:"!
>
> Item was changed:
>   ----- Method: Context>>reactivateHandlers (in category 'private-exceptions') -----
>   reactivateHandlers
>         "Private - sent to exception handler context only (on:do:).
>         Reactivate all the handlers into the chain"
>
> +       self reactivateHandler.
> -       self tempAt: 3 put: true. "this is temporary handlerActive in #on:do:"
>         self nextHandlerContext reactivateHandlers!
>
> Item was added:
> + ----- Method: Context>>reactivateHandlersUpTo: (in category 'private-exceptions') -----
> + reactivateHandlersUpTo: aHandlerContext
> +       "Private - sent to exception handler context only (on:do:).
> +       Reactivate the inner handlers into the chain, up to, but not including, aHandlerContext"
> +
> +       self == aHandlerContext ifTrue: [^self].
> +       self reactivateHandler.
> +       self nextHandlerContext reactivateHandlersUpTo: aHandlerContext!
>
> Item was added:
> + ----- Method: Context>>reactivateHandlersWhich:upTo: (in category 'private-exceptions') -----
> + reactivateHandlersWhich: selectBlock upTo: aHandlerContext
> +       "Private - sent to exception handler context only (on:do:).
> +       Reactivate the inner handlers into the chain, up to, but not including, aHandlerContext, that satisfy the selectBlock predicate"
> +
> +       self == aHandlerContext ifTrue: [^self].
> +       (selectBlock value: self) ifTrue: [self reactivateHandler].
> +       self nextHandlerContext reactivateHandlersWhich: selectBlock upTo: aHandlerContext!
>
> Item was changed:
>   ----- Method: Context>>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 reactivateHandler. aBlock value]
> +               ensure: [self deactivateHandler]!
> -       ^ [self tempAt: 3 put: true. aBlock value]
> -               ensure: [self tempAt: 3 put: false]!
>
> Item was added:
> + ----- Method: Context>>willHandleSignal: (in category 'private-exceptions') -----
> + willHandleSignal: exception
> +       "Sent to handler (on:do:) contexts only."
> +
> +       ^self isHandlerActive and: [(self tempAt: 1) handles: exception]
> + !
>
> Item was added:
> + ----- Method: Exception>>reactivateHandlersUpTo: (in category 'priv handling') -----
> + reactivateHandlersUpTo: aHandlerContext
> +       "reactivate all the exception handlers in the context chain"
> +       self canSearchForSignalerContext
> +               ifTrue: [signalContext nextHandlerContext reactivateHandlersUpTo: aHandlerContext]!
>
> Item was added:
> + ----- Method: UndefinedObject>>reactivateHandlersUpTo: (in category 'bottom context') -----
> + reactivateHandlersUpTo: aHandlerContext
> +
> +       ^ self!
>
> Item was added:
> + ----- Method: UndefinedObject>>reactivateHandlersWhich:upTo: (in category 'bottom context') -----
> + reactivateHandlersWhich: selectBlock upTo: aHandlerContext
> +
> +       ^ self!
>
>

> I'd like to suggest the following change to really make handling `return`
> the same whether it's called explicitly or not: The last line should send
> `return: val` to exception instead of self - the `exception return` calls
> `handlerContext return` and at the moment it's true the `self` is the
> handlerContext. But in theory someone can e.g. change `return` definition
> and then the two returns won't be the same... Plus I think this is more
> consistent and readable. Thanks,
>
> handleSignal: exception
> "Sent to handler (on:do:) contexts only.  If my exception class (first
> arg)
> handles exception
> and the handler is active 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:)."
>
> | val |
> (self willHandleSignal: exception) ifFalse:
> [self deactivateHandler.
> ^self nextHandlerContext handleSignal: exception].
>
> exception privHandlerContext: self contextTag.
> self deactivateHandler.  "disable self while executing handle block"
> val := self fireHandlerActionWith: exception.
> + exception return: val  "return as default action if not otherwise
> directed
> in handle block"
> - self return: val  "return from self if not otherwise directed in handle
> block"