Exited segmentation fault Struct in C

Question

So I have a struct and I want to make a function with a loop taking from user inputs and store them into the struct. But after 1 loop the program crashes with segmentation fault and I can't find the problem.

Here is the error:

> clang-7 -pthread -lm -o main main.c
> ./main
4
ath
67
68
thes
exited, segmentation fault
>

Here is the code:

#define STR 100000
typedef struct city{
 float x;
 float y;
 char *name;
}City;

City *GetCities(int *N){
int i;
City *p;
char c;
scanf("%d",&*N);
p=malloc(sizeof(City));
p->name=malloc(STR*sizeof(char));

if (p->name==NULL){
  printf("Could not find enough memory");
}

for (i=0; i<*N; i++){
   while((c = getchar()) !='
' && c!= EOF);
   fgets(p[i].name,STR,stdin);
   p[strcspn(p[i].name,"
")].name="";
   p[i].name=realloc(p[i].name,(strlen(p[i].name)+1)*sizeof(char));
   scanf("%f ",&p[i].x);
   scanf("%f",&p[i].y);
} 
return p;
}

question from:https://stackoverflow.com/questions/65858442/exited-segmentation-fault-struct-in-c

Answer 1

This one will work:

//includes were missing
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define STR 100000
typedef struct city{
 float x;
 float y;
 char *name;
}City;

City *GetCities(int *N){
  int i;
  char c;
  City *list, *city;
  //N is already a pointer so using a '&*' is confusing and I'm unsure whether this is at all valid syntax
  scanf("%d", N);
  //allocate enough memory! multiplied by number of cities
  list = malloc(sizeof(City) * (*N));
  
  for (i=0; i < *N; i++) {
     //use pointer arithmetic to get the current city from the allocated block
     //this needs to be done only once, now you can go on and reuse it extensively
     city = list + i;
     
     city->name = malloc(STR * sizeof(char));
     if (city->name==NULL){
       printf("Could not find enough memory");
     }
     while((c = getchar()) !='
' && c!= EOF);
     //i hope rest is clear
     fgets(city->name, STR, stdin);
//use city->name[strlen(city->name)-1]='' instead?
     city->name[strcspn(city->name,"
")]='';
     //at least you didn't forget the +1 in the realloc! :-)
     city->name = realloc(city->name,(strlen(city->name)+1)*sizeof(char));
     scanf("%f ", &city->x);
     scanf("%f",  &city->y);
  }
  
  return list;
}

//please also show the main, but I guess it was something like this
int main () {
    int i, n;
    City *cities, *city;
    cities = GetCities(&n);
    for (i=0; i < n; i++) {
        city = cities + i;
        printf("The %dth city "%s" got coordinates x=%f and y=%f!
", i, city->name, city->x, city->y);
        //don't forget to free the name
        free(city->name);
    }
    //don't forget to free the memory
    free(cities);
}

I would also recommend to use a smaller line length buffer and run fgets in a loop to save ram space.