how to use scanf() to input data direct to a char pointer in a struct

Question

The following code compiles but I get an access violation at runtime.

typedef struct login
{
    char *name;
    char *pw;
}login;

 int _tmain(int argc, _TCHAR* argv[])
{
    login user1, user2;
    GetUser(user1);

    printf("\nUN is %s, PW is %s", user1.name, user1.pw);

    GetUser(user2);

    printf("\nUN is %s, PW is %s", user2.name, user2.pw);

    getch();
    return 0;
}

void GetUser(login &user)
{
    char *name;
    name = (char*)malloc(20);
    printf("Enter User Name: ");
    fflush(stdin);
    scanf("%s", name);
    user.name = name;

    printf("Enter password: ");
    user.pw = GetPassword();
    free(name);
}

If I change the char *name; to a char[20]; in the struct, the code works fine.

I modified the above code using malloc but after the second call to GetUser(user2); user1.name == user2.name. user1.pw and user2.pw are as expected

You are using reference type in the code. But the question has c tag — user7171623
– user7171623, Commented Apr 30, 2017 at 23:27

faffaffaff · Accepted Answer · 2017-04-30 23:21:40Z

2

char* does not point to anything. You need to malloc enough bytes to hold the input you are reading.

answered Apr 30, 2017 at 23:21

faffaffaff

3,57918 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

dmaelect Over a year ago

would it be better practice to change the struct to char name[20]; or to change the GetUser(...) function?

Collectives™ on Stack Overflow

how to use scanf() to input data direct to a char pointer in a struct

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related