[Pharo-project] getting rid of Symbol >> new: ?

Sheridan Mahoney sheridan at sheridan-mahoney.com
Thu Dec 10 01:59:24 CET 2009

Adrian Lienhard wrote:
> On Dec 8, 2009, at 12:08 , Mariano Martinez Peck wrote:
>> On Fri, Dec 4, 2009 at 12:05 PM, Adrian Lienhard <adi at netstyle.ch>  
>> wrote:
>> When you are creating your root of objects and you put symbols  
>> inside, they
>> are not put in ourPointers but in ByteArray.
>> This is due to the fact that the only object who is pointing to that  
>> symbol
>> is inside the segment ?
> To be precise, the symbols are also pointed to by the symbol table,  
> but only by weak references. Since image segments use the GC mark  
> logic, these pointers are not considered.

Martin and I had been working towards the idea that ImageSegments should
never create non-Canonical symbols, and the user should not have to use
manual techniques to preserve symbols they are interested in keeping alive.

I ended up getting stuck however, in trying to discover what process
goes through while it is installing objects - ImageSegment #install  has a
call to an
unimplemented method   #readFromFileWithSymbols  which it seems it should be
using, but isn't....(wha' the?)

	"This operation retrieves the segment if necessary from file storage,
installs it in memory, and replaces (using become:) all the root stubs with
the reconstructed roots of the segment."

	| newRoots |
	state = #onFile ifTrue: [self readFromFile].
	state = #onFileWithSymbols ifTrue: [self readFromFileWithSymbols.
		endMarker := segment nextObject. 	"for enumeration of objects"
		endMarker == 0 ifTrue: [endMarker := 'End' clone]].
	(state = #active) | (state = #imported) ifFalse: [self errorWrongState].
	newRoots := self loadSegmentFrom: segment outPointers: outPointers.
	state = #imported 
		ifTrue: ["just came in from exported file"
			arrayOfRoots := newRoots]
		ifFalse: [
			arrayOfRoots elementsForwardIdentityTo: newRoots].
	state := #inactive.
	Beeper beepPrimitive

I think the next step in this trajectory is to trace is how the state is
set - right now it is kind of a mystery...

Does this seem reasonable?



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