CODEWITHSUNDEEP
c++pointersmemory-management
Rasmus
Rasmus

Reputation: 1685

Deleting double pointer causes heap corruption

I am using a double pointer but when I try to delete it it causes Heap Corruption: CRT detected that the application wrote to memory after end of heap. It "crashes" inside the destructor of the object:

Map::~Map()
{
    for(int i = 0; i < mTilesLength; i++)
        delete mTiles[i];

    delete[] mTiles;
}

mTiles is declared something like this:

Tile **mTiles = NULL;
mTiles = new Tile *[mTilesLength];

for(int i = 0; i < mTilesLength; i++)
    mTiles[i] = new Tile(...);

If notable mTiles is a object of "Tile" which inherits from a object "Sprite" all 3 destructors are set as virtual (map, tile, sprite), not sure if that makes any difference but seemed to work until now.

Upvotes: 0

Views: 3113

Answers (1)

Yakk - Adam Nevraumont
Yakk - Adam Nevraumont

Reputation: 275770

The code you posted does not seem to have any problems in it. I created a simple, self contained, compiling (and correct) example from it:

struct Tile {int x; Tile():x(7) {}};

struct Map {
  Tile **mTiles;
  int mTilesLength;
  Map(int TilesLength_);
  ~Map();
};
Map::~Map()
{
  for(int i = 0; i < mTilesLength; i++) {
    delete mTiles[i];
  }

  delete[] mTiles;
}
Map::Map(int TilesLength_):
  mTiles(),
  mTilesLength(TilesLength_)
{
  mTiles = new Tile *[mTilesLength];

  for(int i = 0; i < mTilesLength; i++) {
    mTiles[i] = new Tile();
  }
}
int main() {
  Map* m = new Map(1000);
  delete m;
}

I compiled and ran it <- link, and nothing bad was noticed.

Your problem lies in code you have not shared with us. In order to find the code that is causing the problem and ask the right question, go here: http://sscce.org/

Then take your code and start trimming parts off it until the code is simple, yet still demonstrates your heap corruption. Keep copies of each version as you trim away irrelevant code so you don't skip over the part where the problem occurs (this is one of the many reasons you want a version control system even on your personal projects).

Upvotes: 1

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