I'm trying to pass a pointer to an array of struct. This code should create an array of struct, writes to the vars in struct, and then prints them out (which works). Then I want to pass a pointer of that array of struct to another function and print out the array of struts.
#define PORT_NUMBER 5100
#define MAX_CLIENTS 5
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
typedef struct thread_args
{
int client_number;
int connected;
char client_name[1024];
} client;
void pass_func(client* clients[])
int main()
{
struct thread_args clients[MAX_CLIENTS];
int i;
for(i =0; i < MAX_CLIENTS; i++)
{
clients[i].client_number=i;
strcpy(clients[i].client_name, "BOBBY");
}
for(i =0; i < MAX_CLIENTS; i++)
{
printf("%d | %s\n", clients[i].client_number=i, clients[i].client_name);
}
printf("\n\n");
pass_func(&clients);
}
void pass_func(client* clients[])
{
int i;
for(i =0; i < MAX_CLIENTS; i++)
{
printf("%d | %s\n", clients[i]->client_number=i, clients[i]->client_name);
}
}
And this is the output:
$ gcc TEST.c -lpthread -o TEST.out
TEST.c: In function ‘main’:
TEST.c:41:3: warning: passing argument 1 of ‘pass_func’ from incompatible pointer type [enabled by default]
TEST.c:22:6: note: expected ‘struct thread_args **’ but argument is of type ‘struct thread_args (*)[5]’
$ ./TEST.out
0 | BOBBY
1 | BOBBY
2 | BOBBY
3 | BOBBY
4 | BOBBY
Segmentation fault
I've done about an hour of research and can't figure out why this is not working. Most of the examples I find are for C++, but not C. (And yes I know many of the header files I've included are not necessary for this code; this is just a segment of my original code.)
pass_func
expects an array of pointers to client
void pass_func(client* clients[]);
but you pass it
pass_func(&clients);
a pointer to an array of client
s. So the client
clients[i]
is interpreted as a pointer to client
in pass_func
, but of course the bit-pattern is not a valid pointer to client
, hence you're trying to access memory you shouldn't and get a segfault.
Either pass an array of pointers, or declare pass_func
void pass_func(client *clients);
(and then pass pass_func(clients)
without the address-operator in main).
Your compiler warned you about passing an incompatible pointer type, though.
void pass_func(client* clients[])
{
int i;
for(i =0; i < MAX_CLIENTS; i++)
{
printf("%d | %s\n", (*clients)[i].client_number=i, (*clients)[i].client_name);
}
}
this will be fine.
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