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; found the function that fills the vector and it seems to be causing the problems. I use almost the same ...

  1. #16
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    found the function that fills the vector and it seems to be causing the problems. I use almost the same code as in this function within the program and that vector can be cleared without a problem. I've been looking at it for a while but can't pin point the problem. Could someone take a look at it, I must be missing something:
    Code:
    void ReadDataSec(FILE * inp, FSAD &Section , int nExpected)
    {
    	char line[110];
    	int  check;
    	int newline =0, endcount=0;
    	DataLine dl;
    
    	int size = nExpected*2 +1;
    
    	while ( fgets(line, sizeof line, inp) != NULL) // reads in a line of text from file
    	{
    		dl.Param = dl.Label=dl.SFactor=dl.SigBits=dl.Bit30=dl.Bit31=dl.Max=dl.Min = '\0';
    		newline =0;
    
    		if (strncmp(line, "\n", 1) == 0)
    			newline =1;
    
    		check = (sscanf(line, "%s %d %f %d %d %d %f %f", dl.Param, &dl.Label,
                       &dl.SFactor, &dl.SigBits, &dl.Bit30, &dl.Bit31, &dl.Max, &dl.Min)); 
    		
    		if ( strncmp(dl.Param, "ENDL", 4) == 0 && newline ==0) // Exit if at the end of a section
    		{
    			dl.Label=dl.SFactor=dl.SigBits=dl.Bit30=dl.Bit31=dl.Max=dl.Min='\0';
    			
    			Section.vectDL.push_back(dl);
    			break;
             }
    
    		if ( strcmp(dl.Param, "END") == 0 && newline == 0) // set all fields to 0 
    at the end of subsection marker
    		{
    			dl.Label=dl.SFactor=dl.SigBits=dl.Bit30=dl.Bit31=dl.Max=dl.Min='\0';
    			
    			Section.vectDL.push_back(dl);
    			
    			endcount++;
    		}
    
    		if (strncmp(dl.Param, "END", 3) != 0 && newline ==0) // If the line is not
     the end of subsection marker, copy the line into global vector
    		{
    			
    			if (check == 8)
    			{	
    				Section.vectDL.push_back(dl);
    			}
    
    			else if (check == 6)
    			{
    				dl.Max=dl.Min='\0';
    
    				Section.vectDL.push_back(dl);
    			}
    		}
    
    		
    	}
    
    	if (endcount != nExpected)
    		EXIT_FAILURE;
    }
    Last edited by earth_angel; 08-25-2005 at 01:48 PM.
    Everything is relative...

  2. #17
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    The orange line in the above code was removed, and the error does not occure anymore. However, the file is not parsed properly now. I hope it won't take me another million hours to fix that.

    I just don't understand why would resettign the structure variable would cause a amemory leak?
    Everything is relative...

  3. #18
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    > dl.Param = dl.Label=dl.SFactor=dl.SigBits=dl.Bit30=dl.Bit31=d l.Max=dl.Min = '\0';
    You should not be setting dl.Param to '\0'. Since this is a char array (assumption based on your sscanf()), you would lose the memory address. To clear dl.Param, use:
    Code:
    dl.Param[0] = '\0';

  4. #19
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    And since dl.Label and the rest are numbers, you should zero them with:
    Code:
    ... = 0;
    instead of:
    Code:
    ... = '\0';
    The two statements are equivalent, but the second is usually used for strings.

  5. #20
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    dl.Param is a CString.

    and I'm using MS VC++ 6.0
    Everything is relative...

  6. #21
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    I've amde the change from '\0' to 0, but I kept getting the demage error. So I figured that if I can't fix this problem I'll go around it. So I used an array of dl's instead of reusing and resetting the same one. This way I only use the data I just read into that cell and there is no demage error further on. That array is destryed automatically on the stack, so I don't have to worry about it.
    I have to admit I really don't understand how clearing that variable would cause a demage problem with the vector being filled later on.
    Everything is relative...

  7. #22
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    I don't believe it's a good idea to pass a CString directly to sscanf(). I would try something like:
    Code:
    check = (sscanf(line, "%s %d %f %d %d %d %f %f", dl.Param.GetBufferSetLength(sizeof(line)), &dl.Label,
                       &dl.SFactor, &dl.SigBits, &dl.Bit30, &dl.Bit31, &dl.Max, &dl.Min));
    And then just leave out dl.Param in your clearing line:
    Code:
    dl.Label=dl.SFactor=dl.SigBits=dl.Bit30=dl.Bit31=dl.Max=dl.Min = 0;

  8. #23
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    Then I cannot call any other cString function until I call ReleaseBuffer(). and I'd like to work with it before I release it.
    Everything is relative...

  9. #24
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    >Then I cannot call any other cString function until I call ReleaseBuffer()
    I don't think that's true with GetBufferSetLength(), only with GetBuffer().

    But irregardless, CString is a class, and cannot be passed directly to sscanf(). You can read a CString like a char array, but not write to one as a char array.

  10. #25
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    OK. I see. that makes a lot of sense, I always froget about it being a class in these cases.

    Thanks.
    Everything is relative...

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