Segmentation Fault issue , C language , use of malloc in structures

Question

Keep getting segmentation fault error with this C code , putting an & before output somehow resulted with the right values but again ended up with a segmentation issue, using calloc instead results in null values. I can definitely go for the approach with allocating memeory in the main() itself but tried felt like this should also work, question attached:

Make a structure with (i) Name of the employee (ii) Date of birth which is a collection of {day, month, year} (iii) Address which is a collection of {house number, zip code and state}. Write a 'C' program to read and display the data of N employees using pointers to array of structures

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

typedef struct Dob{
    int day;
    int month;
    int year;
}dob;

typedef struct Address{
    int h_num;
    int zip;
    char* state;
}address;

typedef struct employee{
    char* name;
    dob date;
    address ad;
}emp;

void enterEmp(emp* e,int i){
    e[i].name = malloc(30*sizeof(char*));
    printf("Enter name : ");
    scanf("%s",e[i].name);
    printf("Enter dob in dd/mm/yy format : ");
    scanf("%d %d %d",&e[i].date.day,&e[i].date.month,&e[i].date.year);
    printf("Enter house number and zip code : ");
    scanf("%d %d",&e[i].ad.h_num,&e[i].ad.zip);
    printf("Enter state : ");
    e[i].ad.state = malloc(20*sizeof(char*));
    scanf("%s",e[i].ad.state);

    printf("\n Name : %s Date: %d/%d/%d Address- h-no: %d zip: %d state: %s \n",e[i].name,e[i].date.day,e[i].date.month,e[i].date.year,e[i].ad.h_num,e[i].ad.zip,e[i].ad.state);
}

void printEmp(emp *e,int len){
    int i;
    for(i=0;i<len;i++){
        printf("\n Name : %s Date: %d/%d/%d Address- h-no: %d zip: %d state: %s \n",e[i].name,&e[i].date.day,&e[i].date.month,&e[i].date.year,&e[i].ad.h_num,&e[i].ad.zip,e[i].ad.state);
    }
}

int main(){
    int choice;
    int len = 0;
    do{
        printf("\nEnter choice (1)Enter Employee (2)Read Employee (3)Exit : ");
        emp* e = malloc(10*sizeof(emp));
        scanf("%d",&choice);
        switch(choice){
        case 1:
            enterEmp(e,len);
            len++;
            break;
        case 2:
            printEmp(e,len);
            break;
        case 3:
            exit(0);
            break;
        default:
            printf("Invalid Input");
            break;
        }
    }while(1);
    return 0;
}

Answer 1

The main problem is that you're allocating the array e inside the loop. So each time through the loop you create a new array and lose all the data that was entered from previous iterations. When you try to print the employees, you're printing the contents of an uninitialized array. That's causing the segmentation fault (or null pointers if you use calloc()).

Move the line

    emp* e = malloc(10*sizeof(emp));

to before the loop.

Other problems:

• The format string for reading a date should be %d/%d/%d. You should check the return value from scanf() to ensure that it's parsing the input properly.
• If you want to allow the user to type a full name, use fgets() to read a whole line, not scanf(), because %s only reads a single word. You'll also need to remove the trailing newline from this; see fgets() includes the newline at the end.
• malloc(XX*sizeof(char*)) should be malloc(XX*sizeof(char)) when allocating strings. This doesn't actually cause problems because it just allocates more memory than you intended (pointers are 4 or 8 bytes).