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Background

I wrote a function named removeIllegalMoveFromMovesCell to remove data from some variables, let's call it x and y for now. The value of x does change inside the function but will not update outside of the function.

Calling the method:

removeIllegalMoveFromMovesCell(movesArr[row][col].moves,&(movesArr[row][col].size), row, col);

Explaining the variables

x and y variables that was mentioned above are movesArr[row][col].moves and movesArr[row][col].size, they are based on those structs:

typedef struct _move {
    char rows;
    char cols;
} move;

typedef struct _movesArray {
   unsigned int size;
   move* moves;
} movesArray;

And here is how I create them:

movesArray* arr = (movesArray*)malloc(sizeof(movesArray));

move* movesArr1 = (move*)malloc(2 * sizeof(move));
move* movesArr2 = (move*)malloc(2 * sizeof(move));

move move1, move2, move3, move4;

move1.rows = -2;
move1.cols = 3;

move2.rows = 1;
move2.cols = 3;

move3.rows = -2;
move3.cols = 5;

move4.rows = 1;
move4.cols = 2;

movesArr1[0] = move1;
movesArr1[1] = move2;

movesArr2[0] = move3;
movesArr2[1] = move4;

arr[0].size = 2;
arr[1].size = 2;

arr[0].moves = movesArr1;
arr[1].moves = movesArr2;

removeIllegalMoveFromMovesCell method:

void removeIllegalMoveFromMovesCell(move* moves, int* size, int currRow, int currCol) {
int i;
int cloneIndex = 0;

move* movesClone = (move*)malloc((*size - 1) * sizeof(move));

for (i = 0; i < *size; i++) {
    if (!isMoveOutOfBounds(currRow, currCol,
        getPureNumber(moves[i].rows), getPureNumber(moves[i].cols))) {

        movesClone[cloneIndex].rows = moves[i].rows;
        movesClone[cloneIndex].cols = moves[i].cols;
        cloneIndex++;
    }
}

moves = (move*)realloc(moves, cloneIndex * sizeof(move));

for (i = 0; i < cloneIndex; i++) {
    moves[i] = movesClone[i];
}

*size = cloneIndex;

}

The Problem and what I have tried so far:

While size variable changes outside of the method (And by that changing movesArr[row][col].size), moves variable receive all of movesClone variable inside the method and will change its value inside the method but won't change outside of it (movesArr[row][col].moves).

move is acting as a local variable although I passed his reference and not its value, I cannot understand why it won't change outside of the method

Extra info:

Here is getPureNumber function that is used inside removeIllegalMoveFromMovesCell

int getPureNumber(char c) {//simple return `movesArr[row][col].size` as number
if (c < 0)
    return c - 0;
return c;
}
Tamir Abutbul
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    `moves` **is** a local variable within the function. In C all parameters are passed by value. You only modify the local copy of `moves`. There must be some dupes around.... – Gerhardh Apr 23 '20 at 12:49
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    Side note: While you won't notice any change in `moves` outside that function, the memory where it points to **is** affected by your `realloc` call. You might end up with a pointer to invalid memory – Gerhardh Apr 23 '20 at 12:52
  • @Gerhardh, thx for the comment, but actually I had a version of the function where I received move as `move** moves` and it did not worked. I will look at your linkes and try to find out what I did wrong. – Tamir Abutbul Apr 23 '20 at 12:57

0 Answers0