在 C 中通过函数调用和参数使用指针时出现语法错误

Question

I am getting a syntax error when trying to allocate space for a multidimensional matrix. I am new to coding in C, so anything will help. The error occurs when trying to access the matrix structure elements in the read_matrix function. The syntax error is "expression must have struct or union type". Where the error is produced is commented out in the read_matrix function.

typedef struct {

int *elements;
int rows;
int columns;

} matrix;

void main() {

matrix a, b, c;

void read_matrix(matrix *);
void deallocate(matrix *);
void print(matrix);
matrix add(matrix, matrix);
matrix subtract(matrix, matrix);
matrix multiply(matrix, matrix);

read_matrix(&a);
read_matrix(&b);

c = add(a, b);

deallocate(&c);
c = subtract(a, b);

deallocate(&c);
c = multiply(a, b);

}

void read_matrix(matrix *z) {

int d1, d2, i, x, y, val;

printf("What is the first dimension of the array? ");
scanf("%d", &d1);

printf("What is the second dimension of the array? ");
scanf("%d", &d2);

*z.elements = (int *)calloc(d2, sizeof(int));
*z.rows = d1;
*z.columns = d2;        
    /* error here. It isn't letting me access the 
      elements/rows/columns of the matrix */

/* additional code below here */
}

Answer 1

Operator . has higher precedence than unary operator * , which means that if you want to access struct members through a pointer z using * -and- . combination, you have to use parentheses. It your case it should be

(*z).elements = ...

Alternatively you can use -> operator

z->elements = ...

And it is supposed to be int main() , not void main()