CODEWITHSUNDEEP
cstructsegmentation-faultscanf
RhumB
RhumB

Reputation: 141

C dynamically allocating struct, seg fault when using scanf

#include <stdio.h>  
#include <stdlib.h>
struct Person {
  char* name;
  int age;
};

void printit(struct Person *person) {
    printf("%s %d \n",person->name,person->age);
}

int main(int argc, char** argv) {
  struct Person *p = malloc(sizeof(struct Person));
  printf("Enter name: ");
  scanf("%s", p->name);
  printf("Enter age: ");
  scanf("%d", &(p->age));
  printit(p);
  free(p);
}

Enter name: asdf

Segmentation fault: 11

I don't know why it is giving segmentation fault....

Upvotes: 0

Views: 174

Answers (1)

Haris
Haris

Reputation: 12272

You allocated memory for the struct.

But you did not allocate memory where p->name would point to

Add this to your code.

struct Person *p = malloc(sizeof(struct Person));
p->name = malloc(100);

EDIT

No type should be explicitly allocated space inside a struct.

When you did

struct Person *p = malloc(sizeof(struct Person));

space gets allocated for name and age both. But notice that name is a pointer variable. Space has been allocated for the pointer variable, but not where the pointer will point to.

It is like when you do

char* p;

The variable p is created, space is allocated for it, but if you want to use it, you have two options.

1) Either make it point to some existing allocated memory

char* p;
char arr[10];
p = arr;

2) Or allocate memory where it will point at.

char* p = malloc(sizeof(char));

Upvotes: 5

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