Question

I’m working on a C program that generates a doubly linked list of “records”.

I’ve got my structs prototyped as follows:

struct custRec(char[20] name, char[50] address, char[20] city,
         char[2] stateAbbreviation, int zipCode, float balance);
struct linkedRec(custRec storedRec, custRec* nextRec, custRec* prevRec);

Specifically, for my custRec struct, is it valid to use char[20] name instead of char[] name?

By “valid”, I mean — I’m trying to limit the “name” field to exactly 19 characters (+ null terminator). Should I worry about length elsewhere and make the struct accept char arrays of any length?

Answer 1

This syntax is incorrect (I misread the question at first because they look like function declarations, not structure definitions):

struct custRec(char[20] name, char[50] address, char[20] city,
         char[2] stateAbbreviation, int zipCode, float balance);
struct linkedRec(custRec storedRec, custRec* nextRec, custRec* prevRec);

You probably meant:

typedef struct custRec
{
    char  name[20];
    char  address[50];
    char  city[20];
    char  stateAbbreviation[2];
    int   zipCode;
    float balance;
} custRec;  // Necessary because question is about C, not C++

typedef struct linkedRec
{
    custRec  storedRec;
    custRec *nextRec;
    custRec *prevRec;
} linkedRec;

I note that in the US, state abbreviations are 2 characters, so you probably need to use char state[3] to allow for the terminating null.

This is now syntactically valid. When you copy data into the fields of the custRec, you will need to be careful to ensure that your copying does not overflow the bounds. The compiler does not enforce the lengths.

You will need to check, therefore, inside the function that the strings passed to you do not exceed the limits you expect.

If you prefer not to impose limits on the lengths, all the string structure members can be made into char * and you can dynamically allocate the memory for arbitrary length strings. But that is probably not a good idea for US state abbreviations; there you do want to enforce the ‘2 characters plus '\0'‘ limit.