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How a function can set and get information from a structure in C

I wrote the following code which I am trying to set and get information from the structure via get and set functions. However, when I compile and run the program, it does not display any information from the input. Where is my fault?

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

typedef struct Information{
    int _id;
    char* _name;
    char* _family;
} Information;

void setInformation(Information* arg_struct){
    printf("What is your name? ");
    scanf("%s %s", arg_struct->_name, arg_struct->_family);
    printf("What is your id? ");
    scanf("%d", &arg_struct->_id);
}

void getInformation(Information* arg_struct){
    printf("Your name is %s %s.\n", arg_struct->_name, arg_struct->_family);
    printf("Your id is %d.\n", arg_struct->_id);
}

int main(int argc, char const *argv[]){
    Information *obj = malloc(sizeof(Information));

    setInformation(obj);
    getInformation(obj);

    return 0;
}
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1 answer


you are calling UB because _name

u _family

are pointers pointing to something you don't own (because you don't have malloced

it)

try changing it to

typedef struct Information{
  int _id;
  char _name[SOME_SIZE_1];
  char _family[SOME_SIZE_2];
}Information;`


Or, if you want to stay with pointers instead of arrays, you must malloc it before using pointers, so in your set function add 2 malloc statements:

void setInformation(Information* arg_struct){
  arg_struct->_name = malloc(SOME_SIZE_1);
  arg_struct->_family = malloc(SOME_SIZE_2);
  printf("What is your name? ");
  scanf("%s %s", arg_struct->_name, arg_struct->_family);
  printf("What is your id? ");
  scanf("%d", &arg_struct->_id);
}

but if you are allocating memory, remember to free it when you are done

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