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digitalmars.D - deleting objects caused "Finalization error" when threading

reply Huang Guan <gdxxhg gmail.com> writes:
Hi, I am still writing my Web Server program and I still can not go through the
problems that might be caused by GC. I often catch the exception "Finalization
error" when a connection is being deleted. 

As I have been accustomed to deleting objects when I don't use it( Want to
release memory quickly ), I wrote many "delete" statements. I think the problem
above happens when a thread is deleting a object, but which is at the moment
used by another thread, then it causes the "Finalization error" exception. 

I don't know whether I am right or not.
But as I replaced the "delete obj" instead of "obj = null", the problem seldom
happened.

Do you have any ideas?
Jun 29 2008
parent reply Frank Benoit <keinfarbton googlemail.com> writes:
Huang Guan schrieb:

 Hi, I am still writing my Web Server program and I still can not go through
the problems that might be caused by GC. I often catch the exception
"Finalization error" when a connection is being deleted. 
 
 As I have been accustomed to deleting objects when I don't use it( Want to
release memory quickly ), I wrote many "delete" statements. I think the problem
above happens when a thread is deleting a object, but which is at the moment
used by another thread, then it causes the "Finalization error" exception. 
 
 I don't know whether I am right or not.
 But as I replaced the "delete obj" instead of "obj = null", the problem seldom
happened.
 
 Do you have any ideas?
 


The 'Finalization error' is thrown, if a destructor has thrown an 
exception, which is not allowed.
Jun 29 2008
parent reply "Vladimir Panteleev" <thecybershadow gmail.com> writes:
On Sun, 29 Jun 2008 12:18:37 +0300, Frank Benoit  
<keinfarbton googlemail.com> wrote:


 Huang Guan schrieb:

 Hi, I am still writing my Web Server program and I still can not go  
 through the problems that might be caused by GC. I often catch the  
 exception "Finalization error" when a connection is being deleted.  As  
 I have been accustomed to deleting objects when I don't use it( Want to  
 release memory quickly ), I wrote many "delete" statements. I think the  
 problem above happens when a thread is deleting a object, but which is  
 at the moment used by another thread, then it causes the "Finalization  
 error" exception.  I don't know whether I am right or not.
 But as I replaced the "delete obj" instead of "obj = null", the problem  
 seldom happened.
  Do you have any ideas?


 The 'Finalization error' is thrown, if a destructor has thrown an  
 exception, which is not allowed.


Thus, it's likely that you missed one or more delete statements in your  
code, then the garbage collector picked up an object and its children  
(objects to which only the parent object has references to). Since the  
order the GC destroys unreferenced objects is undetermined, you're  
probably trying to manually delete a child in your parent destructor's  
class, when that child has already been deleted by the GC.

-- 
Best regards,
  Vladimir                          mailto:thecybershadow gmail.com
Jun 29 2008
parent Sean Kelly <sean invisibleduck.org> writes:
== Quote from Vladimir Panteleev (thecybershadow gmail.com)'s article

 On Sun, 29 Jun 2008 12:18:37 +0300, Frank Benoit
 <keinfarbton googlemail.com> wrote:

 Huang Guan schrieb:

 Hi, I am still writing my Web Server program and I still can not go
 through the problems that might be caused by GC. I often catch the
 exception "Finalization error" when a connection is being deleted.  As
 I have been accustomed to deleting objects when I don't use it( Want to
 release memory quickly ), I wrote many "delete" statements. I think the
 problem above happens when a thread is deleting a object, but which is
 at the moment used by another thread, then it causes the "Finalization
 error" exception.  I don't know whether I am right or not.
 But as I replaced the "delete obj" instead of "obj = null", the problem
 seldom happened.
  Do you have any ideas?


 The 'Finalization error' is thrown, if a destructor has thrown an
 exception, which is not allowed.


 Thus, it's likely that you missed one or more delete statements in your
 code, then the garbage collector picked up an object and its children
 (objects to which only the parent object has references to). Since the
 order the GC destroys unreferenced objects is undetermined, you're
 probably trying to manually delete a child in your parent destructor's
 class, when that child has already been deleted by the GC.


FinalizeException should link to the originating exception object, and
both error messages should be displayed when the program exits. Look
at the second message for an idea of where the problem is.  That said,
it's actually good to hear that people are seeing FinalizeExceptions,
because it means they're doing their job :-)


Sean
Jun 30 2008