mess with some pointers...

raven · 06-21-2002, 04:15 PM

hello

i am allocating a little memory block here, and there, and everywhere.

everything seems to be ok. I can allocate the memory i need (for a special struct):

typedef struct member_base
{
char * data;
int number;
struct member_base *next;
}

i can assign to every member of the structure the correct values i need to.
if in the same functuion i read from the appropriate addresses, i get all correct results. but, as soon as I lave the function, and want to access the char pointer in the struct, I get some messed up characters (8 characters).

why, oh why, do I loose the correct addresses?

has anyone a good idea?

thanks

raven

crabboy · 06-21-2002, 08:25 PM

I'd need to see a simple example. It sounds like your variables are going out of scope, but I need to see what and how you are doing it.

Mara · 06-22-2002, 03:04 PM

If the pointer points to a local string, it may give such result.

raven · 06-23-2002, 05:59 PM

to crabboy:

if this is no problem, i will give you the link where you can get the package. the error appears in the queue_handler.c file (if you compile the program, you will get appropriate output) in the find_user function.

http://raven.eplay.ch/www/code/cbant...-1.0.1a.tar.gz

thanks

raven

raven · 06-23-2002, 05:59 PM

to mara:

OK, then this might be the proglem. how do I get around it?

thanks

raven

crabboy · 06-24-2002, 10:18 AM

You were not allocating any space for the strings in your structs. I changed the two char* in your structs to char data[50] and it works. You need to malloc space for the strings that you read in.

Code:

diff -C2 net2_bantumi/Makefile net2_bantumi2/Makefile
*** net2_bantumi/Makefile	Sun May 12 12:10:16 2002
--- net2_bantumi2/Makefile	Mon Jun 24 10:16:03 2002
***************
*** 2,12 ****
  
  all:
! 	$(CC) -c client.c
! 	$(CC) -c server_master.c
! 	$(CC) -c server_game.c
! 	$(CC) -c bantumi_common.c
! 	$(CC) -c queue_handler.c
! 	$(CC) -o client client.o bantumi_common.o
! 	$(CC) -o server server_master.o queue_handler.o bantumi_common.o server_game.o
  
  clean:
--- 2,12 ----
  
  all:
! 	$(CC) -g -c client.c
! 	$(CC) -g -c server_master.c
! 	$(CC) -g -c server_game.c
! 	$(CC) -g -c bantumi_common.c
! 	$(CC) -g -c queue_handler.c
! 	$(CC) -g -o client client.o bantumi_common.o
! 	$(CC) -g -o server server_master.o queue_handler.o bantumi_common.o server_game.o
  
  clean:
***************
*** 16,18 ****
  nice:
  	make all
! 	rm -f *.o
\ No newline at end of file
--- 16,18 ----
  nice:
  	make all
! 	rm -f *.o
diff -C2 net2_bantumi/bantumi.h net2_bantumi2/bantumi.h
*** net2_bantumi/bantumi.h	Sun Jun 16 19:39:06 2002
--- net2_bantumi2/bantumi.h	Mon Jun 24 10:58:16 2002
***************
*** 26,30 ****
  typedef struct base
  	{
! 	char *secret;
  	int conn_num;
  	struct base *next;
--- 26,30 ----
  typedef struct base
  	{
! 	char secret[50];
  	int conn_num;
  	struct base *next;
***************
*** 35,39 ****
  	int type;
  	int len;
! 	char *data;
  	}packet;
  
--- 35,39 ----
  	int type;
  	int len;
! 	char data[50];
  	}packet;
  
diff -C2 net2_bantumi/bantumi_common.c net2_bantumi2/bantumi_common.c
*** net2_bantumi/bantumi_common.c	Fri Jun 21 13:36:33 2002
--- net2_bantumi2/bantumi_common.c	Mon Jun 24 10:59:10 2002
***************
*** 109,113 ****
  		}
  	while(len>0);
! 	r_data->data=buffer_helper;
  	free(buffer);
  	free(buffer_helper);
--- 109,113 ----
  		}
  	while(len>0);
! 	strncpy( r_data->data,buffer_helper, 49 );
  	free(buffer);
  	free(buffer_helper);
Only in net2_bantumi2: client
diff -C2 net2_bantumi/queue_handler.c net2_bantumi2/queue_handler.c
*** net2_bantumi/queue_handler.c	Fri Jun 21 18:25:38 2002
--- net2_bantumi2/queue_handler.c	Mon Jun 24 10:39:26 2002
***************
*** 8,12 ****
  	list=(u_elem *)malloc(sizeof(u_elem));
  	list->conn_num=0;
! 	list->secret=NULL;
  	list->next=NULL;
  	return(list);
--- 8,12 ----
  	list=(u_elem *)malloc(sizeof(u_elem));
  	list->conn_num=0;
! 	strcpy(list->secret,"");
  	list->next=NULL;
  	return(list);
***************
*** 22,26 ****
  		}
  	new=(u_elem *)calloc(sizeof(u_elem),1);
! 	new->secret=secret;
  	new->conn_num=conn_num;
  	new->next=NULL;
--- 22,26 ----
  		}
  	new=(u_elem *)calloc(sizeof(u_elem),1);
! 	strncpy(new->secret,secret,49);
  	new->conn_num=conn_num;
  	new->next=NULL;
Only in net2_bantumi2: server

Output from server.c

Code:

waiting for connection on socket 3
listening on: 4
u_info received containing: type: 3 secret: hello

finding user
new user added: socket: 4 secret: hello

sending: . 0.29.please wait. you are in queue
writing complete
listening on: 5
u_info received containing: type: 3 secret: hello

finding user
comparing hello
 to hello
. more info: 4
removing
done.
playing: 4, 5
broadcasting boards contents...
rotating
sending: . 1.29.00404040404040004040404040400
writing complete
rotating
sending: . 1.29.00404040404040004040404040400
writing complete
broadcasting done...