malloc-關於用自定義函數開辟二維數組的問題

關於用自定義函數開辟二維數組的問題

block1可以正常執行但是block2會出現內存錯誤，想了很久沒有明白。求解答

 #include <stdio.h>
#include <string.h>
#include <stdlib.h>

void** malloc2d(int rows, int cols, int size)
{
  printf("%d\t%d\t%d\n",rows,cols,size);
  int j;
  int rowSize = cols * size;
  int indexSize = rows * sizeof(void *);
  void **a = (void **) malloc(indexSize + rows* rowSize);
  char *dataStart = (char *) a + indexSize;
  for(j = 0; j < rows; j++){
    printf("%d\n",j);
    a[j] = dataStart + j * rowSize;
  }
  return a;
}

int main(){
    int i,rows,cols,row,col;
    rows = cols = 40400;
    row = 3;col = 2;
    int** block1 = (int**)malloc2d(row,col,sizeof(int));
    printf("end of block1,begin of block2\n");
    int** block2 = (int**)malloc2d(rows,cols,sizeof(int));
    free(block1);
    free(block2);
    return 0;
}

最佳回答：

是因為2的數據太多了
void **a = (void **) malloc(indexSize + rows* rowSize);，分配失敗，返回空值