CODEWITHSUNDEEP
carraysstructdynamic-memory-allocation
Melvin
Melvin

Reputation: 439

How to allocate memory for char strings in a struct array?

I am about to create a programm which stores data of students in a list. My question is, how to shall I allocate memory for each char string in my struct array. My code is down below. If there're some other mistakes, please correct me.

#include <stdio.h>
#include <stdlib.h>
#define DATA 10;
#define NAME 10;

typedef struct{
int id;
char *givenname;
char *familyname;

} students;

int main()
{
int answer;
int incr = 0; // Index for students in the list
int datalen = DATA;
int namelen = NAME;

students *studentlist;
studentlist = malloc(datalen * sizeof(students)); // Allocate memory for first ten students

if(NULL == studentlist){
    printf("Error: Couldn't allocate memory\n");
    exit(0);
}

for(incr = 0; incr < datalen; incr ++){
    printf("Add student to the list? Yes(1) No(2)\n");
    scanf("%d", &answer);

    if(answer != 1){
        break;
    }

    studentlist[incr]->givenname = malloc(namelen * sizeof(char)); // Allocate memory for each name
    studentlist[incr]->familyname = malloc(namelen * sizeof(char));

    printf("Insert ID: ");
    scanf("%d", &studentlist[incr].id);

    printf("Insert given name: \n");
    scanf("%s", studentlist[incr].givenname);

    printf("Insert family name: \n");
    scanf("%s", studentlist[incr].familyname);


}

free(studentlist);
free(studentlist.givename);
free(studentlist.familyname);


return 0;
}

Upvotes: 1

Views: 698

Answers (1)

Ratnadeep
Ratnadeep

Reputation: 26

Reference of some elements is wrong:

studentlist[incr]->givenname

It should be:

studentlist[incr].givenname

Allocation of strings seems fine.

Your freeing code needs change:

free(studentlist);
free(studentlist.givename);
free(studentlist.familyname);

You need to free studentlist.givename and studentlist.familyname in a loop and then free studentlist at the end:

for(incr = 0; incr < datalen; incr ++){
   free(studentlist[incr].givename);
   free(studentlist[incr].familyname);
}
free(studentlist);

Upvotes: 1

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