Damage error with clearing a vector

This is a discussion on Damage error with clearing a vector within the C++ Programming forums, part of the General Programming Boards category; Hi, I have a function that fills a vector. It can be run multiple times during the program, but I ...

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    Damage error with clearing a vector

    Hi,
    I have a function that fills a vector. It can be run multiple times during the program, but I don't want it to keep filling the vector as many times as it is run. So I put in a check:
    Code:
         if((FAD.vectDL.empty()) == 0)
    	      FAD.vectDL.clear();
    FAD is a global variable because it is accessed by a bunch of functions. .empty() returns 0 if there is somehting in the vector, but .clear() causes a run-time assertion error( Damage after Normal Block (#112)....).

    Can I not clear a global vector? How would I get rid of this error?
    I tried this without other functions that use the vector. I just ran this function twice in a row.
    Last edited by earth_angel; 08-25-2005 at 08:54 AM.
    Everything is relative...

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    Code:
    if( !vector.empty() )
    {
         vector.clear();
    }

    where vector is replaced by the name of your vector

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    you should consider going from a global variable,
    to passing if by pointer / address / refrence to the
    function

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    Yes, my avatar is stolen anonytmouse's Avatar
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    Quote Originally Posted by earth_angel
    Hi,
    Code:
         if((FAD.vectDL.empty()) == 0)
    	      FAD.vectDL.clear();
    FAD is a global variable because it is accessed by a bunch of functions. .empty() returns 0 if there is somehting in the vector, but .clear() causes a run-time assertion error( Damage after Normal Block (#112)....).
    Something else is going on in your code. Memory errors often blow up in unexpected places. The first step is to check the destructor (if you wrote it) for the object that vectDL contains. Next check for buffer overruns/underruns elsewhere in the program.

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    There is no reason to check for empty before clearing the vector.

    You are always allowed to clear a vector, anonytmouse is correct that the problem is somewhere else in the code.

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    Code:
    if( !vector.empty() )
    {
         vector.clear();
    }
    It's the same thing as == 0, and I tried it too, but same problem. I've been going through my code for the last 3 hours trying to catch something else. but with no luck.

    I didn't write the destructor, but I think I will to make sure I know what's going on.
    Everything is relative...

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    Do you have exceptions set to stop always in the debugger? Break into the debugger and look at the call stack when the assertion happens. Look at the memory of the "this" variable at the different levels of the call stack. Is any of the data weird (like 0xfeeefeee or 0xcdcdcdcd)?

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    >>>Do you have exceptions set to stop always in the debugger?
    I do.
    but it's not an assetion error as I think I said before. It's a debug error. Says "Please try to debug the appliaction".

    I'm checking if I freed/deleted all the arrays and such.
    Everything is relative...

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    ok, I tried to figure this out before but with no luck. Now i get the same demage in block 1180 error if I leave these lines in the code of a different function:
    Code:
    // allocation
          Units = (char **)calloc(NumParam, sizeof(char *));
    
       for(i=0; i<NumParam; ++i)
    	   Units[i] = (char *)calloc(NameLengthU,sizeof(char));
    
    // deletion
    
          for(i=0; i<NumParam; i++)
    		free(Units[i]);    
    
    	free(Units);
    If the red lines are there, I get the same error. Otherwise this function run OK, or at least it seems so.
    Everything is relative...

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    Frequently Quite Prolix dwks's Avatar
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    Code:
            for(i=0; i<NumParam; i++)
    		free(Units[i]);    
    
    	free(Units);
    Well, of course you're getting an illegal operation of some kind. You're freeing the memory twice!

    You shouldn't cast malloc(). And in C++ you shouldn't use malloc() (or calloc()); malloc() doesn't invoke an object's constructor, while new does.
    dwk

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    I know I'm mixing C and C++ and I shouldn't. It's a big job to change all the C into C++ in this project. And I thought since it was allocated for a 2D then I should free the memory individually for all the rows and then the column array. But I guess I don't have to. thanks
    Everything is relative...

  12. #12
    carry on JaWiB's Avatar
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    Can you switch to new and delete?
    How about:
    Code:
    // allocation
          Units = new char* [NumParam];
    
       for(i=0; i<NumParam; i++)
    	   Units[i] = new char[NameLengthU];
    
    // deletion
    
          for(i=0; i<NumParam; i++)
    		delete [] Units[i];    
    
    	delete [] Units;
    I don't know much about calloc and free, but it actually looked ok the way you were doing it (you do have to free each row)
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    >> It's a debug error. Says "Please try to debug the appliaction".

    Make sure you are running the program through the debugger (with Debug->Start, Go or F5) with your IDE. I assume that you are using VC++ and that you are using a Debug build for this testing.

  14. #14
    Yes, my avatar is stolen anonytmouse's Avatar
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    The way you are freeing is fine. A typical cause of this problem is that you are not leaving room for a nul terminator at the end of your strings. Does NameLengthU take account of the nul terminator?

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    Now it does...and it's ok.

    The original vector is still problematic. It may be the same thing. Does sscanf() attach a null terminator is it reads into a string?
    Everything is relative...

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