why segmentation fault? strtok and malloc - c

Question

I have the following code which works perfectly when not using malloc, but when I want to add in dynamic memory allocation it says segmentation fault although it compiles without warnings or errors. Why?
Thanks in advance
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXNUM 30
#define STR 200
#define MAXLEN 40
struct human { //Va
char name[MAXLEN];
char surname[MAXLEN];
int age;
float weight;
};
int main(int argc, char *argv[]) {
char *dlim= ",", *end = "\n", *stop = NULL;
char *tok, *string;
string = (char *)malloc(sizeof(char) * STR);
int i = 0, j = 0;
struct human man[MAXNUM];
FILE *fin = fopen("data.txt", "r");
if (string == NULL) {
printf("Memory not allocated");
}
if (fin == NULL) {
printf("Cannot open file\n");
exit(0);
}
while (fgets(string, sizeof(string), fin)) {
tok = strtok(string, dlim);
strcpy(man[i].name, tok);
tok = strtok(stop, dlim);
strcpy(man[i].surname,tok);
tok = strtok(stop, dlim);
man[i].age = atoi(tok);
tok = strtok(stop, dlim);
man[i].weight = atof(tok);
i++;
}
fclose(fin);
free(string);
j = i;
i = 0;
while (i < j) {
printf("%s %s %d %f \n", man[i].name, man[i].surname, man[i].age, man[i].weight);
i++;
}
return 0;
}

Answer 1

When you make string an allocated array of char, sizeof(string) no longer gives you the size of the array, it gives you the size of the pointer. Therefore you must change the loop to tell fgets the size of your array:
while (fgets(string, STR, fin)) {
...
Or better, if you reallocate the array to size size:
while (fgets(string, size, fin)) {
...