Assign string to pointer in struct - Linked list C

Question

I'm trying to write a program for students linked list in C. Here is the struct:

typedef struct student *studp;
typedef struct student{
    int number;
    char *name;
    char *date;
    unsigned grade;
    studp next;
}stud;

Now I want to write a function which creates new node and assign values to members. I'm not sure how to do it, here is the function:

studp create_stud(int number, char *name, char *date, unsigned grade){
studp item = (studp)malloc(sizeof(stud));
if(!item){
    printf("Cannot allocate memory\n");
    exit(1);
}
item->number = number;
item->name = .....


return item;

} how should I assign the text to the member name and date? can I use the operator '=':

item->name = name;

or I should allocate the memory with malloc() ? and if I use malloc() should I free the pointer in the and of the program or I just can release the node? Thanks!

And calling studp that looks confusingly like strdup() was going to make me crazy. — Iharob Al Asimi
@ToharPingley That you should never do typedef POINTER_TYPE *NON_POINTER_TYPE because it's confusing. — Iharob Al Asimi

user2736738 user2736738 · Accepted Answer · 2018-02-20T18:13:03

item->name = strdup(name);

This will do the trick. In case you don't have this (strdup is a POSIX thing) allocate memory and then use strcpy/memcpy to copy the string pointed by name.

Don't hide pointers inside typedef it's easier to maintain in large codebase - you always have to look back to get what it's type is to write correct code.

Don't cast the return value of malloc and check the return value of strdup just like you did for malloc. Also free the memory allocated using malloc and strdup when you are done working with it.

To show you an example. (Illustration)

stud* item = malloc(sizeof *item);
if(NULL == item){
    perror("Cannot allocate memory\n");
    exit(EXIT_FAILURE);
}
...

free(item->name);
free(item->date);
/* whatever you have allocated */
free(item);

Edit: In case strdup is not there.

item->name = malloc(strlen(name)+1);
if(!item->name){
   perror("malloc");
   exit(EXIT_FAILURE);
}
memcpy(item->name, name, strlen(name)+1);

Assign string to pointer in struct - Linked list C

2 Answers