Question

I’m trying to write a program that reads in entries from a file into a dynamically allocated array of structures using input redirection. My program compiles fine but I’m getting a segmentation fault and I’m having trouble finding the cause.

Here’s my Program:

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

typedef struct StudentData
{
char* name;
char* major;
double gpa;
} Student;

int main()
{
Student* data = (Student*)malloc(sizeof(Student)*5);

int i;
for(i = 0; i < 5; i++)
{
 // allocate memory for name and read input
 data[i].name = malloc(50);
 *(data+i)->name == scanf("%s", (char*)&data[i].name);

 // allocate memory for major and read input
 data[i].major = malloc(30);
 *(data+i)->major == scanf("%s", (char*)&data[i].major);

 // read input for gpa
 (data+i)->gpa == scanf("%lf", &data[i].gpa); 

 //print array
 printf("%s\n%s\n%f\n", data[i].name, data[i].major, data[i].gpa);
 }
}  

Any clues? If it seems obvious it’s because I’m relatively new to C!

Answer 1

*(data+i)->name == scanf("%s", (char*)&data[i].name);

What are you comparing the return value of scanf for? Just remove the first part. Also, data[i].name is already a pointer, so you shouldn’t take the address once again. It should just be:

scanf("%s", data[i].name);  // no & because name is already a pointer

And similarly:

scanf("%s", data[i].major);
scanf("%lf", &data[i].gpa);  // & here because gpa is just a double