ipaq3115
Registered: 12/11/11
Posts: 139
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Posted 30/06/12
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#1
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For some reason when I try to use mem_Free() my program reports -14880 in mem_Heap() and crashes shortly there after. Only happens on the second time I free this particular variable. It is loading an image.
I attached the program. The offending mem_Free() is of 'compassFile' in my touch() function.
I am setting compassFile equal to a buffer entry so that I can pass it into a piece of code I am running. Don't know if that is causing the problems or not.
Attached Files:
 comboProg.4dg (26.44 KB, 8 views)
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ESPsupport
Moderator
Registered: 27/01/09
Posts: 4,279
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Posted 30/06/12
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#2
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If you set one pointer to another you can only free one, if you free it twice all hell will break loose (just guessing that's what's happening)
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ipaq3115
Registered: 12/11/11
Posts: 139
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Posted 30/06/12
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#3
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Yeah, I found that out when I was trying to fix this problem, but I am only trying to free one of the pointers. Will the existence of that second pointer cause problems?
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meldavia
Registered: 18/03/07
Posts: 900
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Posted 30/06/12
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#4
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I think you are freeing more than once.
A good practise is to zero the memory handle.
mem_Free is 'safe' to call with a variable that holds zero, eg
var mychunk;
mychunk :- mem_Alloc(1000); // aloocate
then later.....
mem_Free(mychunk); // free
mychunk := 0; // protect fro inadvertent further freeing of block
.... then later
mem_Free(mychunk); // has no effect as handle is zeroed
__________________
Regards,
Dave
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ipaq3115
Registered: 12/11/11
Posts: 139
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Posted 30/06/12
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#5
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I did try zeroing out one of the pointers but I am opening two different image files. I'll make sure I zero them both when I get back to my computer tomorrow and see if that fixes it.
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ipaq3115
Registered: 12/11/11
Posts: 139
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Posted 04/07/12
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#6
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I made sure I zero both of the places where I am calling mem_Free() and I still have this problem.
The problem does occur after I have freed and then reloaded an image.
e.g. I open the image, then I use it, free it up then go back and open it again. It is after I have freed it the second time that this happens.
I uploaded the updated version of my program, maybe you guys can spot where I'm going wrong, I can upload all the supporting files too if that would help.
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ipaq3115
Registered: 12/11/11
Posts: 139
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Posted 04/07/12
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#7
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Okay, turns out after the second time I ran one of my 4fn files with file_Exec the value of my memory pointer was being changed. I checked the values, after all my code in the 4fn has run, the value is correct but after the 4fn closes and before I have run any other code, the value has changed. Doesn't seem to be anything I did.
Strange problem, but an easy enough fix by storing another copy of the pointer.
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