Re: [Help-smalltalk] Add shortcuts to the visualgst/debugger

[Paolo Bonzini]

Il 30/09/2013 11:33, Holger Hans Peter Freyther ha scritto:
> On Mon, Sep 30, 2013 at 10:47:31AM +0200, Holger Hans Peter Freyther wrote:
> 
> Hi,
> 
> and one more information:
> 
>> So I think what is happening is the following:
>>
>> * We are in the glib mainloop
>> * We get an event (F7.. keyboard)
>> * We use gst_nvmsg_send which will create a new Process (call-in)
>> * We dispatch GtkDebugger>>#stepOver
>> * We want to step/resume another process..
>> * We wait on a semaphore..
>> * The debugged process doesn't run (for whatever reason)
>> * The call-in is waiting on a Semaphore as well
> 
> to make it worse.. the call-in will be suspended because it is
> launching a debugger...
> 
> 'Invalid index 13: index out of range'
> SystemExceptions.IndexOutOfRange(Exception)>>signal (ExcHandling.st:254)
> SystemExceptions.IndexOutOfRange class>>signalOn:withIndex: (SysExcept.st:665)
> String(Object)>>checkIndexableBounds: (Object.st:798)
> String>>at: (String.st:312)
> String(SequenceableCollection)>>replaceFrom:to:with:startingAt: 
> (SeqCollect.st:554)
> String>>replaceFrom:to:with:startingAt: (String.st:296)
> String(ArrayedCollection)>>copyFrom:to: (ArrayColl.st:236)
> ReadStream(PositionableStream)>>copyFrom:to: (PosStream.st:156)
> STInST.RBParser>>errorLine (Parser.star#VFS.ZipFile/RBParser.st:183)
> STInST.RBParser>>parserError: (Parser.star#VFS.ZipFile/RBParser.st:207)
> STInST.RBParser>>parseExpression (Parser.star#VFS.ZipFile/RBParser.st:153)
> STInST.RBParser class>>parseExpression:onError: 
> (Parser.star#VFS.ZipFile/RBParser.st:35)
> STInST.RBParser class>>parseExpression: 
> (Parser.star#VFS.ZipFile/RBParser.st:26)
> UndefinedObject>>executeStatements (a String:1)
>       6         ^self activateHandler: (onDoBlock isNil and: [ self 
> isResumable ])
> 
> The question is.. is this a VisualGST issue or should the VM
> be more robust against such deadlocks? I think we could have
> a couple of 
> 
> if (cur_state == STATE_DISPATCHING && blocking)  
>     {
>       event_loop_unlock ();
>       return;
>     }
> 
> in the vm, like in gst_interpret?
> 
> comments?

After some debugging with Holger, I think the problem is that VisualGST
is not handling the DebuggerReentered exception.

All invocations of #step, #finish: etc. should be wrapped with a
DebuggerReentered exception handler.  You can look at how MiniDebugger
does it.  MiniDebugger (and the Blox debugger too) creates a new
command-loop, but perhaps VisualGST can just change the window title or
something like that.

Paolo