C函数中的多维数组

Question

I have this exercise to make a transpose of a matrix in C. I made a function to check for type n*n but when I'm trying to ask the user for the matrix I don't know how I should declare the array. And I'm getting this compile error "type of formal parameter 1 is incomplete" in the function on the [n2] part.

The parameters of the functions for multi dimensional arrays shouldn't be like this -> int matrix[][n2]. or is cause i'm using a variable and not a constant or a pre defined size. ?

#include <stdio.h>
#define prompt "Dimenção da matriz (nxn) >>"
#define prompt_1 "Introduza os valores : "

void getType( int *n1, int *n2 );
void getMatrix( int matrix[][n2], int lim1, int lim2);
//void trans(int matrix[][n2]);

int main(int argc, char const *argv[]) {
  int n1, n2;
  getType(&n1, &n2);
  int matrix[n1][n2];
  //printf("%dx%d\n", n1, n2);
  getMatrix(matrix, n1, n2);
  //trans(matrix);
  return 0;
}

void getType(int *n1, int *n2){
  printf("%s", prompt );
  scanf("%dx%d", &(*n1), &(*n2));
}

void getMatrix( int matrix[][n2], int lim1, int lim2){
  printf("%s\n", prompt_1 );
  for(int line  = 0; line < lim1; line++ ){
    for(int column = 0; column < lim2; column++){
      printf("Linha %d coluna %d ->", line, column );
      scanf("%d", &matrix[line][column]);
    }
  }
}

Answer 1

The signature should be:

void getMatrix( int lim1, int lim2, int matrix[lim1][lim2] )

You are allowed omit the lim1 inside square brackets but it is good documentation to include it.

The main point is that the variable inside the square brackets must either be a parameter from earlier in the parameter list, or some other variable in scope (which can only be a global variable, but that's usually a bad idea).

Also it would be good to check scanf return value otherwise you may create matrix with garbage dimension.