[Valgrind-users] problem on free()

[Gerald G. <ger...@ya...>]

I've been using valgrind now for quite some time now,
I guess I have improved my coding with it. For a
couple
of days now I've been trying to trace read violation.
The code is quite long but I'll just the describe some
of the areas here.

The code below is a node extraction below for a doubly
linked
list. it handles the start and end node condition and
the last 
part handles the somewhere-in-the-middle condition.
The sections
are identical in procedures except for the position to
operate on,
the node is deleted from the list at the end of each
condition.
Valgrind however reports a misread on the last part of
the function.
Its reporting several places, but its all rooted on
this single 
function. Valgrind doesnt report anything when the
function is operating
on the start and end of the list. dllist.c corresponds
to the last call
to free() at the bottom. Is there anything wrong with
my code or is this
a known bug in valgrind. I'd appreciate any feedback
because I've been
trying to solve this for a couple of days now. Thanks
a lot.

Gerald R. Generoso

Command line options used: -v
Operating system: Redhat 9
GCC version: 3.2.2

==4760== Invalid read of size 4
==4760==    at 0x8049736: dllist_searchList
(dllist.c:969)
==4760==    by 0x8049CB5: main (xsearch.c:68)
==4760==    by 0x40245916: __libc_start_main (in
/lib/libc-2.3.2.so)
==4760==    by 0x804854C: ??? (start.S:81)
==4760==    Address 0x411A43D0 is 12 bytes inside a
block of size 20 free'd
==4760==    at 0x40029961: free
(vg_replace_malloc.c:231)
==4760==    by 0x80490F4: dllist_extractNode
(dllist.c:576)
==4760==    by 0x8049910: dllist_srta_extractNode
(dllist.c:1095)
==4760==    by 0x8049706: dllist_searchList
(dllist.c:955)


/*----------------------------------------------------------------------------*/
int dllist_extractNode(dllist **listNode, 
                       dllist **loadPtr, 
                       fcn **statusObj,
                       char *fileName,
                      int lineNumber)
{
	dllist *nodeObj = (*listNode);
	dllist *tmp_load = (*loadPtr);
	dllist *tmpNode = NULL;
	
	fcn *status = (*statusObj);
        
        errno = 0;
        
        if(!nodeObj)
        {
            fcn_writeMsg(&status,
                         NULL_PTR,
                         "dllist_extractNode",
                         "listNode"IS_NULL,
                         fileName,
                         lineNumber);
                         
            return FAILED;
        }
        
	/*store node here before removing from the list*/
        if(tmp_load)
        {                           
			
	    if((tmp_load->loadObj =
memmove(tmp_load->loadObj,
				            nodeObj->loadObj,
			                    nodeObj->size_loadObj)) ==
NULL)
            {
                fcn_writeMsg(&status,
                             errno,
                             "dllist_extractNode",
                             strerror(errno),
                             fileName,
                             lineNumber);
                             
                return FAILED;
            }
			
	    tmp_load->tagObj = nodeObj->tagObj;
	    tmp_load->size_loadObj = nodeObj->size_loadObj;
			
	    (*loadPtr) = tmp_load;
        }
        
	/*the start of list condition*/
        if(nodeObj->prevNode == NULL)
        {
            tmpNode = nodeObj->nextNode;
            
            if(nodeObj->loadObj)
            {
                free(nodeObj->loadObj);
                nodeObj->loadObj = NULL;
            }
            
            free(nodeObj);  
	    nodeObj = NULL;
            
	    if(tmpNode)
	    {
               tmpNode->prevNode = NULL;     
            }
                                                      
   
	    (*listNode) = tmpNode;
                       
            return SUCCESS;                           
               
        }
        
	/*the end of list condition*/            
        if(nodeObj->nextNode == NULL)
        {
            tmpNode = nodeObj->prevNode;
            
            if(nodeObj->loadObj)
            {
                free(nodeObj->loadObj);
                nodeObj->loadObj = NULL;
            }
            
            free(nodeObj);   
	    nodeObj = NULL;

	    if(tmpNode)
	    {
               tmpNode->nextNode = NULL;        
            }
                                                      
                        
	    (*listNode) = tmpNode;
                            
            return SUCCESS;                           
               
        }
                
        /*somewhere in the middle condition*/
	nodeObj->prevNode->nextNode = nodeObj->nextNode;
        nodeObj->nextNode->prevNode =
nodeObj->prevNode;
		      
        if(nodeObj->loadObj)
        {
            free(nodeObj->loadObj);
            nodeObj->loadObj = NULL;
        }
		
	/*valgrind reports a misread here!*/
	free(nodeObj);
        nodeObj = NULL;
        		                       
    return SUCCESS;
}/*End of dllist_extractNode*/


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