Question

I have declared a structure in my .h file, as such:

struct node{
char* string;
}

I intend this to have created a structure, example, with one member, a character pointer named string.

Now, I figure out how long the string is and malloc an array of appropriate size, taking the input with that.

char* test;
test = (char*) malloc( n * sizeof(char) );

Insofar as I am aware, this has created character pointer test, and has assigned it to point at the head of the array I just malloc’d. I then proceed to assign each array slot to a character that the user has entered, and I read it back out – this all compiles and works appropriately. My problem comes when I try to assign this character pointer to the character pointer in a structure node passed in to this structure, as:

int f1( struct node* new ){

So I try to assign the pointer in the structure to the value of the pointer to the array, like so:

new->string = test;

But I segfault.

To me, this seems like I am assigning a char* to something that expects a char* so this should be working fine…I’m probably missing something stupid, but does anyone have a direction to point me in? Thanks much!

Answer 1

Check your caller of f1() and make sure your parameter is valid.

This will work:

struct node *you = malloc(sizeof(struct node));
if (you)
{
    f1(you);
    free(you);
} 

As will this:

struct node me;
f1(&me);

This will NOT work

struct node *me;
int f1(me);