Question

How would you correct this function in C to prevent buffer overflow?

void nameBuilder()
{
   char fname[10];
   char lname[10];
   char fullname[20];

   printf("Enter your first name: ");
   scanf("%s", fname);

   printf("Enter your last name: ");
   scanf("%s", lname);

   strcat(fullname, fname);
   strcat(fullname, " ");
   strcat(fullname, lname);

   printf("Welcome. %s\n", fullname);
   return;
}

Answer 1

// "while ( (getchar()) != '\n');"
// after "scanf()" statement
// flushes the input buffer

// using it after the “scanf()” statement clears the input buffer and allows the input in the desired container.
void nameBuilder()
{
char fname[10];
char lname[10];
char fullname[20];

printf("Enter your first name: ");
scanf("%s", fname);

   // flushes the standard input
// (clears the input buffer)
while ((getchar()) != '\n');
printf("Enter your last name: ");
scanf("%s", lname);
while ((getchar()) != '\n');
strcat(fullname, fname);
strcat(fullname, " ");
strcat(fullname, lname);
printf("Welcome. %s\n", fullname);
return;
}

/* PLEASE UPVOTE */