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???
08/07/05 20:08
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 		 #98961 - come in
Responding to: ???'s previous message
hi,

De Spiegelaere Nico said:
Also you realy have to make sure, if you let's say save content twice and restore content only ones you could have a problem with getting the write values back.


You are not so far from the real problem. But you come to problem of un-balanced stack usage where you push something and then forget to restore it. The problem I wish to point in is surely the stack pointer usage. But this is not due a programmer "forgets" of popping; the problem comes from the code optimization we do often and often. Try to find it. The answer is in the original post especially when you look at the next lines:
Save This Code
A_SUBROUTINE:
	CALL	SAVE_CONTEXT
; some work
	CALL	RESTORE_CONTEXT
	RET
Try to optimize this piece of code then trace what happens when optimization utilizes both subroutines I posted and the answer will be clean!

Regards,
Oleg

List of 53 messages in thread
TopicAuthorDate
Week puzzle            01/01/70 00:00      
   why is one a subroutine and another a ta            01/01/70 00:00      
      no RTOS            01/01/70 00:00      
   last there was discussion, in this an an            01/01/70 00:00      
      week            01/01/70 00:00      
   Last pushed in - first popped out            01/01/70 00:00      
      come in            01/01/70 00:00      
   Will it work?            01/01/70 00:00      
      Yes it will            01/01/70 00:00      
         Mmmmm?            01/01/70 00:00      
         And another thought            01/01/70 00:00      
            it's perfectly safe...            01/01/70 00:00      
               Still not convinced            01/01/70 00:00      
                  dangers            01/01/70 00:00      
                     Choices            01/01/70 00:00      
                        the same in real life            01/01/70 00:00      
                           Smart and Neat Code            01/01/70 00:00      
                              are you a math major? :)            01/01/70 00:00      
                                 Not a maths major            01/01/70 00:00      
                        yes            01/01/70 00:00      
                  what dangerous            01/01/70 00:00      
                     If misuse is chronic...            01/01/70 00:00      
   CALL + RET != JUMP            01/01/70 00:00      
      ?????????            01/01/70 00:00      
         oops Oleg Has the code to manage it sorr            01/01/70 00:00      
            return address            01/01/70 00:00      
      you got it!            01/01/70 00:00      
         Thanks for the puzzle :-)            01/01/70 00:00      
   a question            01/01/70 00:00      
      why not            01/01/70 00:00      
         well            01/01/70 00:00      
            optimisation            01/01/70 00:00      
               I have seen that happen when the require            01/01/70 00:00      
                  it's the same than if you miss a push or            01/01/70 00:00      
         The Trick is:            01/01/70 00:00      
   the answer            01/01/70 00:00      
      you never answered            01/01/70 00:00      
         solid or intermittent problem            01/01/70 00:00      
            difference between solid or intermittent            01/01/70 00:00      
   Why Push!!!            01/01/70 00:00      
      side effect            01/01/70 00:00      
         Another SAVE_CONTEXT            01/01/70 00:00      
            Sounds like a housekeeping nightmare            01/01/70 00:00      
               Sounds like a housekeeping nightmare            01/01/70 00:00      
               it IS a housekeeping nightmare            01/01/70 00:00      
                  Erik            01/01/70 00:00      
                     Pay no attention            01/01/70 00:00      
                        Donald, if you took the time to read wha            01/01/70 00:00      
                           Reading difficulties            01/01/70 00:00      
                              sorry, used wrong word            01/01/70 00:00      
                     no problem with any post, just with stat            01/01/70 00:00      
            maybe because            01/01/70 00:00      
      eh?            01/01/70 00:00      

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