Adding strings and values to a hash table in C [duplicate] - c

Question

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Why does a pointer to array need to be cast before being passed as parameter to a function with array type argument?
(3 answers)
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I'm trying to add a persons and number to a hash table, but when I'm adding these values I get the incompatible pointer types passing 'char *[20]' to parameter of type 'char *' error.
I'm also getting an EXC_BAD_ACCESS (code=1, address=0x140) when assigning the customer_number to the index.
typedef struct
{
char *first_name[20];
int customer_number;
} Customer;
Customer *list[10];
int hash_table[10];
void insert(char *first_name, int customer_number)
{
int index = calculate_hash(customer_number);
list[index]->customer_number = customer_number;
strcpy(list[index]->first_name, first_name);
hash_table[index]=customer_number;
}
int main(void)
{
insert("Chris", 9999);
return 0;
}
When the insert is passed a first name and phone_number, I want these to be added to the hash.

Answer 1

There are a number of issues here. You need to look again at pointers and buffer overflows...
#define CUSTOMER_NAME_MAX_LEN 20
typedef struct
{
char first_name[CUSTOMER_NAME_MAX_LEN + 1];
int customer_number;
} Customer;
Customer list[10];
int hash_table[10];
int calculate_hash(int customer_number) {
return 3;
}
void insert(char *first_name, int customer_number)
{
int index = calculate_hash(customer_number);
list[index].customer_number = customer_number;
list[index].first_name[CUSTOMER_NAME_MAX_LEN] = 0; // Avoid buffer overflow.
strncpy(list[index].first_name, first_name, CUSTOMER_NAME_MAX_LEN);
hash_table[index]=customer_number;
}
int main(void)
{
insert("Chris", 9999);
printf("%s %i\n", list[3].first_name, list[3].customer_number);
return 0;
}
// Outputs Chris 9999