Passing a 2D array to a thread function

Question

I want to pass a 2D array into my thread function that must have parameters (void *args). When I want to iterate through the array in my function, I keep running into the following error:

subscripted value is not an array, pointer, or vector sumArrays += args[i][j] ;

I am not sure how to get around this. The values passed in to the thread function are also integers.

Any help would be awesome!

Thanks

Answer 1

Instead of using a struct , one can also create a local variable with the correct type:

#define ROWS 3
#define COLS 3

/* Sum the values in a 3x3 array. */
/* This would be your thread entry point. */
void sum(void *args) {
    int (*array)[ROWS][COLS] = args; // Declare and initialize a pointer to a ROWSxCOLS array of ints.

    int row;
    int col;
    int total = 0;
    for(row = 0; row < ROWS; row++) {
        for (col = 0; col < COLS; col++) {
            total += (*array)[row][col]; // Access [row][col] from the array pointed to by "array".
        }
    }

    (void) total;
}

int main(int argc, char** argv) {
    int arrayIn[ROWS][COLS] = {
        {0, 1, 2},
        {3, 4, 5},
        {6, 7, 8}
    };

    sum(arrayIn);
}

The struct solution suggested by @ian-abbott has the benefit of allowing the easy addition of more complex data being passed to your thread (such as the dimensions of the array).