"
COPYRIGHT (c) 1993 by Claus Gittinger
All Rights Reserved
This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice. This software may not
be provided or otherwise made available to, or used by, any
other person. No title to or ownership of the software is
hereby transferred.
"
Object subclass:#Exception
instanceVariableNames:'signal parameter errorString
suspendedContext handlerContext
rejected
resumeBlock rejectBlock'
classVariableNames:'EmergencyHandler'
poolDictionaries:''
category:'Kernel-Exceptions'
!
Exception comment:'
COPYRIGHT (c) 1993 by Claus Gittinger
All Rights Reserved
$Header: /cvs/stx/stx/libbasic/Exception.st,v 1.11 1994-08-22 12:19:19 claus Exp $
'!
!Exception class methodsFor:'documentation'!
copyright
"
COPYRIGHT (c) 1993 by Claus Gittinger
All Rights Reserved
This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice. This software may not
be provided or otherwise made available to, or used by, any
other person. No title to or ownership of the software is
hereby transferred.
"
!
version
"
$Header: /cvs/stx/stx/libbasic/Exception.st,v 1.11 1994-08-22 12:19:19 claus Exp $
"
!
documentation
"
Instances of Exception are passed to a Signal handling block as argument.
The handler block may perform various actions by sending corresponding messages
to the exception handler. The following actions are possible:
reject - dont handle this signal;
another handler will be searched for,
upper in the calling hierarchy
proceed - continue after the Signal>>raise, returning nil as value
proceedWith:val - same, but return val from Signal>>raise
return - return from the Signal>>handle:do:, returning nil as value
return:val - same, but return val from Signal>>handle:do:
restart - restart the Signal>>handle:do:, after repairing
Via the Exception object, the handler can also query the state of execution,
where the Signal was raised, where the handler is, the signal which caused
the error and the errorString passed when the signal was raised:
instance variables:
signal - the signal which caused the exception
parameter - a parameter (if any) which was passed when raising
the signal (only if raised with #raiseWith:aParameter)
errorString - an errorString (only if raised wiith #raiseWith:errorString:)
suspendedContext- the context where the signal raise occured
handlerContext - the context of the handler itself
resumeBlock - private to the exception; needed to perform resume action
rejectBlock - private to the exception; needed to perfomr reject action
In case of an unhandled signal raise, Exceptions EmergenyHandler (a two-argument
block) will be evaluated, getting the exception and context as arguments.
The default emergeny handler will enter the debugger.
For applications, which do not want Debuggers to come up, other handlers are
possible.
For example: to get the typical C++ behavior, use:
Exception emergencyHandler:[:ex :con | Smalltalk exitWithCoreDump]
instance variables:
signal <Signal> the signal which is responsible for all of this
parameter <Object> the parameter passed to raiseRequestWith: or nil (for raise)
errorString <String> the signals notifierString, or the string given to raise
suspendedContext <Context> the context, in which the raise occured
handlerContext <Context> the handlers (if found) context
resumeBlock <Block> used during handler evaluation to get back
rejectBlock <Block> used during handler evaluation to reject
Class variables:
EmergencyHandler <Block> this block is evaluated, if no handler was defined
for a signal (i.e. this one is responsible for the
unhandled exception debugger).
Having this being a block allows to globally catch
these errors - even when no enclosing handler-scope
around the erronous code exists.
(as the catch/through does).
"
! !
!Exception class methodsFor:'defaults'!
emergencyHandler
"return the handler used for unhandled exceptions"
"
set it up, when called the first time
"
EmergencyHandler isNil ifTrue:[
EmergencyHandler := [:ex |
(ex signal) enterDebuggerWith:(ex errorString).
]
].
^ EmergencyHandler
!
emergencyHandler:aOneArgBlock
"set the handler used for unhandled exceptions"
EmergencyHandler := aOneArgBlock
! !
!Exception methodsFor:'accessing'!
signal
"return the signal, that caused the exception"
^ signal
!
parameter
"return the parameter passsed with the signal raise
(or nil, if there was none)"
^ parameter
!
errorString
"return the errorString passsed with the signal raise
(or nil, if there was none)"
^ errorString
!
handlerContext
"return the context of the handler"
^ handlerContext
!
suspendedContext
"return the context in which the raise occured"
^ suspendedContext
!
rejected
"return true, if the exception handler rejected.
(only valid after handler execution)"
^ rejected
! !
!Exception methodsFor:'setup'!
signal:aSignal parameter:aParameter errorString:aString suspendedContext:sContext
"set the fields usable for inspection by the handler
- only to be sent from the signal when raising"
signal := aSignal.
parameter := aParameter.
errorString := aString.
suspendedContext := sContext.
!
handlerContext:aContext
"set the context of the handler.
- only to be sent from the signal when raising"
handlerContext := aContext
!
rejectBlock:aBlock
"this is meant to be sent by Signal only"
rejected := false.
rejectBlock := aBlock
!
resumeBlock:aBlock
"this is meant to be sent by Signal only"
resumeBlock := aBlock
! !
!Exception methodsFor:'handler actions'!
reject
"handler decided not to handle this signal -
system will look for another handler"
rejected := true.
rejectBlock value
!
resume
"Continue after the raise - the raise returns nil"
resumeBlock value:nil
!
resumeWith:value
"Continue after the raise - the raise returns value"
resumeBlock value:value
!
proceed
"Continue after the raise - the raise returns nil"
resumeBlock value:nil
!
proceedWith:value
"Continue after the raise - the raise returns value"
resumeBlock value:value
!
return
"Continue after the handle:do: - the handle:do: returns nil"
handlerContext unwind
!
returnWith:value
"Continue after the handle:do: - the handle:do: returns value"
handlerContext unwind:value
!
restart
"restart the handle:do: - usually after some repair work is done
in handler"
handlerContext restart
! !