memory leak in vector <int>

This is a discussion on memory leak in vector <int> within the C++ Programming forums, part of the General Programming Boards category; I implement a vector Code: vector<int> v; which reads in integers by Code: v.push_back(item); // add item to end of ...

  1. #1
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    memory leak in vector <int>

    I implement a vector
    Code:
    vector<int> v;
    which reads in integers by

    Code:
    v.push_back(item); // add item to end of vector
    When my program ends, I call
    Code:
    v.clear();
    to clear v

    But I have memory leak from it.
    Code:
    Detected memory leaks!
    
    Dumping objects ->
    
    {132} normal block at 0x0035CD10, 36 bytes long.
    
    Data: < > 02 00 00 00 03 00 00 00 04 00 00 00 05 00 00 00 
    
    Object dump complete.
    Why is it so? I check my memory leak by using

    Code:
    #include <crtdbg.h>
    
    _CrtDumpMemoryLeaks();
    in Microsoft Visual Studio 2005

  2. #2
    Super Moderator VirtualAce's Avatar
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    item looks suspect.

    More code please. What is item and how are you allocating it?

  3. #3
    Devil's Advocate SlyMaelstrom's Avatar
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    Ditto to Bubba... if item is allocated dynamically, I don't believe clear does any deletion on it. Plus, 36 bytes seems off to me. Wouldn't it be 32 more likely? I don't know what the overhead would be.
    Sent from my iPadŽ

  4. #4
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    this is a part of my code, d->ReadData() is the function which reads in the number. d is of class DATA, which i declare
    Code:
    	do {
    		d->ReadData();
    		if (!d->v.empty()) {
    			if (d->v.size()+tranTol >= (unsigned int)support) {
    				arr = NewArray_db(d->v.size() + 1); // +1 to store the transaction number too 	
    				sort( d->v.begin(), d->v.end() );  
    				arr[0] = d->v.size();       
    				j=1;
    				for (unsigned int i=0; i<d->v.size(); i++) {
    					arr[j++] = d->v.at(i);	  	        
    					bucket_item[d->v.at(i)]++;
    					//cout << d->v[i] <<" ";
    				}
    				//cout <<endl;
    			}
    			else {
    				arr = NewArray_db(1);
    				arr[0] = 0;       
    			}
    			tempt[index++] = arr;   
    			for (int z=0; z<d->v.size(); z++) {
    				d->v[z] = 0;
    			}
    			d->v.clear();      
    			d->v.resize(0);
    		}
    		else { //the transaction read in is empty
    			arr = NewArray_db(1);
    			arr[0] = 0;       
    			tempt[index++] = arr;   
    			d->v.clear();      
    		}
    	} while (!feof(d->in));


    Code:
    void Data::ReadData() {
    	do {
    		usi pos=0, item=0;
    		c = getc(in);
    
    		if (c=='-') {//if read in a -1, skip it
    			c = getc(in);
    			c = getc(in);
    		}
    
    		while((c >= '0') && (c <= '9')) {
    			item *=10;
    			item += usi(c)-usi('0'); 
    			c = getc(in);
    			pos++;
    		}
    
    		if (pos) {
    			v.push_back(item); // add item to end of vector	  
    		}
    
    		if (c == '\n')
    			return;
    
    	} while (!feof(in));
    }

  5. #5
    Cat
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    Seems far more likely you're failing to properly delete an object you allocated, like d, or arr, or something.

    BTW -- your code really needs descriptive variable names, and comments.
    You ever try a pink golf ball, Wally? Why, the wind shear on a pink ball alone can take the head clean off a 90 pound midget at 300 yards.

  6. #6
    Reverse Engineer maxorator's Avatar
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    Always use braces whenever you're doing a statement.
    "The Internet treats censorship as damage and routes around it." - John Gilmore

  7. #7
    Devil's Advocate SlyMaelstrom's Avatar
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    Quote Originally Posted by maxorator
    Always use braces whenever you're doing a statement.
    I don't know why... you mean in situations like this?
    Code:
    if (exit == true)
        return 0;
    I almost never use braces on single statement conditionals and loops. Braces can get annoying to me and they're easily replaced with good spacing, which I try to use. His braces seem fine to me. His indentation is weird but that's because he's probably using tabs not spaces. The only real issue I have with his style is the way he puts comments after opening braces. In my opinion:
    Code:
    /* This is ugly */
    if (condition) { // This is a comment
       // Doing stuff
    }
    /* End ugly */
    
    /* Better to do this */
    if (condition) // This is a comment
    {
        // Doing stuff
    }
    
    /* Or this */
    if (condition) {
       // This is a comment
       //Doing stuff
    }
    
    /* In my opinion */
    Sent from my iPadŽ

  8. #8
    Reverse Engineer maxorator's Avatar
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    TABS RULE
    Code:
    /* Yeah, I like this too: Or this */
    if (condition) {
       // This is a comment
       //Doing stuff
    }
    "The Internet treats censorship as damage and routes around it." - John Gilmore

  9. #9
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    I tried something simple

    Code:
    	vector<int> g;
    	g.push_back(10);
    	g.clear();
    	_CrtDumpMemoryLeaks();
    but there is still memory leak.

  10. #10
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    found the solution here! you got to free vector by youself

    http://www.gamedev.net/community/for...opic_id=391685

  11. #11
    C++ Witch laserlight's Avatar
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    My interpretation of that is that it does not mean that your program has a memory leak: rather, at the point where the check is made, the memory simply has not been deallocated yet, even though the objects themselves have been destroyed.
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  12. #12
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    yes, i thought of that too, but is there anyway to double confirm? I think I will play safe than be sorry and use the solution above.

    hey, i'm from singapore too! =)

  13. #13
    and the hat of wrongness Salem's Avatar
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    > {132} normal block at 0x0035CD10, 36 bytes long.
    Well if you go on to read the manual a bit more on the memory leak debugging, the {nnn} is the allocation number, which you can set a breakpoint on (the manual tells you how).

    When you know which allocation that is, you can then decide whether it's one you really need to worry about, or wether it is some "system" overhead block which has nothing to do with your code.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  14. #14
    vae victus! skorman00's Avatar
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    yes, i thought of that too, but is there anyway to double confirm?
    I'm not sure what your main() function looks like, but rigging it up like this helps:
    Code:
    void Run()
    {
      // do everything in here
    }
    
    int main()
    {
      Run();
      _CrtDumpMemoryLeaks();
    }
    This way, you know all the automatic destructors have been called by the time you call the dump. This will still report any heap memory allocated by any global or static objects you have though.

    if you #define _CRTDBG_MAP_ALLOC before you #include <crtdbg.h>, it should give you the file and line number where the allocation was made, but it doesn't always work correctly. That define defines new as an inline function that takes __LINE__ and __FILE__, but I've had lots of trouble trying to get that function to actually compile inline. If it doesn't, it will tell you all allocations happen in that function instead of the one that called new, which sucks. I swear I've gotten it to work before, but I can't remember how.

  15. #15
    carry on JaWiB's Avatar
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    Perhaps try the method from this thread.
    "Think not but that I know these things; or think
    I know them not: not therefore am I short
    Of knowing what I ought."
    -John Milton, Paradise Regained (1671)

    "Work hard and it might happen."
    -XSquared

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