pointint to an array from within a structure

**rupurt** · 10-20-2005

alright i seem to have hit a brick wall with all the errors im getting on this one.

what i want to do is point to my multidimensional array history in the structure and pass this around to various functions so that i can put things into the history array.

i keep getting the compilation error "warning: assignment from incompatible pointer type"

any help to solve this is great

Code:

struct clientconn
{
	int							sockfd;
	int 							listenfd;
	char 							*cliIP;
	struct history_entry 	**history;
};

struct clientconn		*conn;
struct history_entry history[100][10];

conn = malloc(sizeof(struct clientconn));
conn->sockfd = Accept(listenfd, cliaddr, &len);
conn->listenfd = listenfd;
conn->cliIP = inet_ntoa(cliaddr->sin_addr);
conn->history = history;

**quzah** · 10-20-2005

A pointer to a pointer is not the same as a pointer to an array of arrays. Here is a FAQ on the topic. You might want to browse the whole index of the topic of Arrays and Pointers.

Quzah.

**cbastard** · 10-20-2005

Code:

int p[10];
int *x;
x=p;

By increasing number of *(star) before a pointer it appears you can increase the number of [](brackets) after an array like

Code:

int p[][];
int **x;
x=p

But **x is a pointer to a pointer.
To expain it further like you if you have to pass a single dim array to function you can do this

Code:

int p[];
test(int *p);

now suppose you have to pass two dim array,you cant pass array like this

Code:

int p[][];
test(int **p);

**rupurt** · 10-20-2005

ok so i went backe and changed the structure to only point to the array with

Code:

stuct history_entry history[10][100];

struct history_entry 	*historyptr;

but how do i assign the historyptr to the array? i tried

Code:

conn->historyptr = history;

as well as 

conn->historyptr = &history;

but both give me "warning: assignment from incompatible pointer type"

**quzah** · 10-20-2005

Well that's wrong too. I take it you didn't bother reading either of the links I provided.

Quzah.

**cbastard** · 10-20-2005

Code:

struct clientconn
{
	int							sockfd;
	int 							listenfd;
	char 							*cliIP;
	struct history_entry 	*history[];
};

may be something like this

**quzah** · 10-20-2005

No, that's wrong too. That's an array of pointers to struct history_entry. You too should go read the links I provided.

Quzah.

**cbastard** · 10-20-2005

Oh sorry i mean to say

Code:

struct clientconn
{
	int							sockfd;
	int 							listenfd;
	char 							*cliIP;
	struct history_entry 	(*history)[];
};

my bad

>>No, that's wrong too. That's an array of pointers to struct history_entry. You too should go read the links I provided.
yeah sure i will.

Thread: pointint to an array from within a structure

Thread Tools

Search Thread

Display

pointint to an array from within a structure

Similar Threads

Structure or Array?

linear search for structure (record) array

Type and nontype parameters w/overloading

Merge sort please

Struct *** initialization