Reputation: 1
I am trying to allocate a dynamic array of Country objects for my school project. I have malloc'd the array in main()
function and I am reallocating it in a add_country()
function. but it seems to give me realloc invalid ponter error. Could someone help? This is the minimal reproducable code.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int count = 0;
typedef struct test_Country
{
char name[20];
int gold;
int silver;
int bronze;
} test_Country;
test_Country *addtest_Country(test_Country test_Country_obj, test_Country*array)
{
int flag = 0;
printf("%s\n", "before realloc");
test_Country *new_array;
new_array = realloc(array, sizeof(test_Country *) * (count + 1));
printf("%s\n", "after realloc");
//array[count].name = (char *)malloc(strlen(test_Country_obj.name) + 1);
if (count == 0)
{
strcpy(new_array[0].name, test_Country_obj.name);
}
else
{
for (int i = 0; i < count; i++)
{
if (strcasecmp(new_array[i].name, test_Country_obj.name) == 0)
{
printf("%s", "test_Country already added\n");
flag = 1;
break;
}
}
}
if (flag == 0)
{
strcpy(new_array[count].name, test_Country_obj.name);
test_Country_obj.gold = 0;
test_Country_obj.silver = 0;
test_Country_obj.bronze = 0;
new_array[count] = test_Country_obj;
count = count + 1;
}
flag = 0;
return new_array;
}
int main()
{
char choice;
test_Country *array = malloc(sizeof(test_Country));
test_Country test_Country_obj;
printf("%s", "Enter your choice : ");
scanf("%s", &choice);
//fgets(ptr, 80, stdin);
//sscanf(ptr, "%c %s %d %d %d", &choice, test_Country_obj.name, &test_Country_obj.gold, &test_Country_obj.silver, &test_Country_obj.bronze);
//printf("%s", &choice);
while (choice != 'E')
{
printf("%s", "Enter test_Country name : ");
scanf("%s", test_Country_obj.name);
array = addtest_Country(test_Country_obj, array);
//printf("%d%s", count, "is count");
printf("%s", "Enter your choice : ");
scanf("%s", &choice);
}
}
I cant seem to understand what is wrong.
Upvotes: 0
Views: 76
Reputation: 75062
char choice;
scanf("%s", &choice);
is bad. choice
has only room for one character, so it can hold only strings upto zero characters. (the one-character room is for terminating null-character). Trying to store strings longer than zero character leads to dangerous out-of-range write and it may destroy data around that.
To avoid out-of-range write, you should allocate enough elements and specify the maximum length to read. The maximum length should be the buffer size minus one for terminating null-character.
char choice[16]; /* allocate enough elements */
scanf("%15s", choice); /* specify the maximum length */
After that, choice
in the while
and switch
should be replaced with choice[0]
to judge by the first character. Another way is using strcmp()
to check the whole string.
Upvotes: 2