Thread: Lists and Char Pointers - Last element overwriting all others

Hi,

I have one list that contains multiple smaller lists. Each smaller list contains char arrays (well that where things get messy with pointers etc).

So the problem is that that contents of the smaller lists kept getting overwritten by the last element and I can’t understand why although I’m sure it’s something to with pointers and I have tried numerous different things including using strcpy. This is part of a large project and simulator so I’ve just included the relevant code below: I wrote a small for loop at the end to just print out the contents of the list to check that it was over writing.

I’m very stuck on this so any help appreciated.

Code:

List*		obstacle_list;
List*		input;
char 		line[1000];
char		*token = OPC_NIL;	

obstacle_list = op_prg_list_create();

fgets(line, sizeof(line), some_file);

while (line != OPC_NIL))
{
	token = strtok(line, "\t"); //Pull the string apart into tokens using the tabs
	input = op_prg_list_create();
	while (token != NULL)		
           {
           	   if (op_prg_list_size(input) == 0)
		op_prg_list_insert(input,token,OPC_LISTPOS_HEAD);
	   else
		op_prg_list_insert(input,token,OPC_LISTPOS_TAIL);

               token = strtok (NULL, "\t");
           }		
	
            if (op_prg_list_size(obstacle_list) == 0)
		op_prg_list_insert(obstacle_list,input,OPC_LISTPOS_HEAD);
	else
		op_prg_list_insert(obstacle_list,input,OPC_LISTPOS_TAIL);
		
	fgets(line, sizeof(line), some_file);				
}

size_ob_list = op_prg_list_size (obstacle_list);
for (k = 0; k <size_ob_list; k++)
{
	line_coord_list = op_prg_list_create();
	line_coord_list = op_prg_list_access (obstacle_list, k);
					
	count_inner_list = op_prg_list_size (line_coord_list);
	for (j=0; j< count_inner_list; j++)
	{
		coords = (char*)op_prg_list_access (line_coord_list, j);
		printf("%c", coords);		
	}
}

how does your input loop terminate? the value of the variable 'line', which is an address on the stack, doesn't change and will never be 0, assuming your OPC_NIL == 0.

fgets : On success, the function returns str. If the end-of-file is encountered while attempting to read a character, the eof indicator is set (feof). If this happens before any characters could be read, the pointer returned is a null pointer (and the contents of str remain unchanged).
you should terminate the loop when fgets returns 0.