请问问大侠们，什么原因？

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


#define MAX_LENGTH  60
#define END_OF_ARRAY    '\0'


typedef struct week{
    char name[MAX_LENGTH];
    int  number;
    } Week;


int TestAllocSpace(int num, char **list)
{
    if (num == 0)
        *list = (char *)calloc(1, sizeof(Week));
    else
        *list = (char *)realloc(*list, sizeof(Week)*(num+1));

    return(0);
}


int GetLine(FILE *fp, char string[MAX_LENGTH])
{
  int len;

    while (fgets(string, MAX_LENGTH, fp) != NULL)
    {
        len = strlen(string);
        if (len > 1)
        {
            string[len-1] = END_OF_ARRAY;
            return (0);
        }
    }

  return (-1);
}
   

int main(int argc, char *argv[])
{
  char line[MAX_LENGTH];
  Week *list=NULL, *p;
  int i, num=0;
  FILE  *fp;
 
    if( argc < 2 )
        exit(-1);

    fp = fopen( argv[1], "r");
    if( fp == NULL )
        exit(-1);

    while ( !GetLine(fp, line) )
    {
        TestAllocSpace(num, &list);
        strcpy(list[num].name, line);
        
        p = &(list[num]);
        p->number = num;
        
        num++;
    }


    for(i = num-1; i >= 0; i--)
        printf("%d) %s\n", list[i].number, list[i].name);

    free(list);

    fclose(fp);
   
  return(0);
}
该程序中子函数TestAllocSpace(int num, char **list)中第二个形参为char型，但主函数中调用该子函数时传递的参数为我week结构类型的，该程序可以运行成功，请问问大侠们，什么原因？