Allocate memory for char array pointer of struct inside function - c

Question

I was looking around for about one day on how to solve my problem. I find solutions for problems similar to mine but when I apply changes error : error: request for member 'mark' in something not a structure or union keeps showing.
What I have so far is a struct and I want to initialize it on a function call.
Edit my code:
typedef struct student * Student;
struct student {
char *mark; /* or array[2] like array[0] = 'A' , array[1] = 'B' */
int age;
int weight;
};
typedef enum{
MEMORY_GOOD,
MEMORY_BAD} Status;
int main(int argc, char* argv[]) {
int status = 0;
Student john
/* Function call to allocate memory*/
status = initMemory(&john);
return(0);
}
Status initMemory(Student *_st){
_st = malloc(sizeof(Student));
printf("Storage size for student : %d \n", sizeof(_st));
if(_st == NULL)
{
return MEMORY_BAD;
}
_st->mark = malloc(2*sizeof(char)); /* error: request for member 'mark' in something not a structure or union */
return MEMORY_GOOD;
}

Answer 1

Just replace
_st->mark = malloc(2 * sizeof(char));
With
(*_st)->mark = malloc(2 * sizeof(char));
_st is a pointer wich content is the address of the struct, so ...
1) first you need to dereference _st, and...
2) second, with the value you get, you point to the field mark
That's all !

Answer 2

try to avoid too many *s in your code,
was able to run it after making some changes, please refer to the ideone link in the next line.
http://ideone.com/Ow2D2m
#include<stdio.h>
#include<stdlib.h>
typedef struct student* Student; // taking Student as pointer to Struct
int initMemory(Student );
struct student {
char* mark; /* or array[2] like array[0] = 'A' , array[1] = 'B' */
int age;
int weight;
};
typedef enum{
MEMORY_GOOD,
MEMORY_BAD} Status;
int main(int argc, char* argv[]) {
Status status;
Student john; /* Pointer to struct */
/* Function call to allocate memory*/
status = initMemory(john);
printf("got status code %d",status);
}
int initMemory(Student _st){
_st = (Student)malloc(sizeof(Student));
printf("Storage size for student : %d \n", sizeof(_st));
if(_st == NULL)
{
return MEMORY_BAD;
} else {
char* _tmp = malloc(2*sizeof(char)); /* error: request for member 'mark' in something not a structure or union */
_st->mark = _tmp;
return MEMORY_GOOD;
}
}