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[bug #6743] Distinct NSNumbers with the same value dealloc each other


From: nobody
Subject: [bug #6743] Distinct NSNumbers with the same value dealloc each other
Date: Tue, 25 Nov 2003 03:00:10 -0500
User-agent: SonyEricssonT610 OmniWeb/4.2-v435.2

=================== BUG #6743: LATEST MODIFICATIONS ==================
http://savannah.gnu.org/bugs/?func=detailbug&bug_id=6743&group_id=99

Changes by: Richard Frith-Macdonald <address@hidden>
Date: Tue 11/25/2003 at 08:00 (GMT)

------------------ Additional Follow-up Comments ----------------------------
I think raising an exception upon an attempt to deallocate a cached NSNumber 
would be a nice feature.



=================== BUG #6743: FULL BUG SNAPSHOT ===================


Submitted by: moseshall               Project: GNUstep                      
Submitted on: Tue 11/25/2003 at 03:06
Category:  Base/Foundation            Severity:  5 - Major                  
Bug Group:  Bug                       Resolution:  None                     
Assigned to:  None                    Status:  Open                         

Summary:  Distinct NSNumbers with the same value dealloc each other

Original Submission:  Distinct NSNumbers with the *same value* can dealloc each 
other. The following code snippet crashes gnustep-base 1.7.3 possibly because 
of NSNumber caching. If I don't call [n1 release] there is no crash. If this is 
due to caching strategy, then it can make NSNumber very fragile when numbers 
are expected to persist as long as retained.



#include <Foundation/Foundation.h>



int main (int argc, const char *argv[], const char *env[]) 

{

  NSNumber* n1 = [NSNumber numberWithLong:1];

  NSNumber* n2 = [NSNumber numberWithLong:1];

  NSLog(@"%@(%d)n", n1, [n1 retainCount]);

  NSLog(@"%@(%d)n", n2, [n2 retainCount]);

  [n1 release]; //<--problem here

  // The next line crashes. n2 has gone away!

  NSLog(@"%@(%d)n", n2, [n2 retainCount]);

  return 0;

}



Thanks for your attention.

Brian 'Moses' Hall

address@hidden

Follow-up Comments
*******************

-------------------------------------------------------
Date: Tue 11/25/2003 at 08:00       By: CaS
I think raising an exception upon an attempt to deallocate a cached NSNumber 
would be a nice feature.

-------------------------------------------------------
Date: Tue 11/25/2003 at 06:24       By: CaS
There is a bug in the test program ... it releases an object it does not own, 
so a crash does not seem unreasonable (in the general case releasing objects 
you don't own is bound to cause crashes).



Is the report a suggestion that the library should be changed to crash 
elsewhere, or to have code added to watch for this case and raise an exception 
or something similar, or perhaps to simply ignore the extra release and keep on 
going?




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For detailed info, follow this link:
http://savannah.gnu.org/bugs/?func=detailbug&bug_id=6743&group_id=99

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