code giving segmentation fault

Anuradha12345 · 08-10-2012, 01:01 AM

Here is the code in c which giving me segmentation fault

node = (TrieNode *) malloc(sizeof(TrieNode));
memset(node, 0,sizeof(TrieNode));
can any body help me out. After execution it gives segmentation fault and it makes my system hang.I m using Debian linux. Thanking in advance.

here is the gdb o/p:

Trie root after creation 8055028
Reading file: /home/anuradha/ufilter/blacklists/spyware/domains
Reading file: /home/anuradha/ufilter/blacklists/humor/domains
Reading file: /home/anuradha/ufilter/blacklists/arjel/domains
Reading file: /home/anuradha/ufilter/blacklists/mixed_adult/domains

Program received signal SIGSEGV, Segmentation fault.
0xb7f00dde in memset () from /lib/libc.so.6

kauuttt · 08-10-2012, 01:05 AM

Please post the whole code, otherwise it is difficult to help you out.

Anuradha12345 · 08-10-2012, 01:20 AM

Thanks for reply. Here the code.
void trie_insert(Trie *trie, char *key, void *value)
{
TrieNode **rover;
TrieNode *node;
char *p;
int c;
static int node_memory;
/* Cannot insert NULL values */

if (value == NULL) {
return;
}

/* Search down the trie until we reach the end of string,
* creating nodes as necessary */

rover = &trie->root_node;
p = key;

while (*p!='\0') {

node = *rover;

if (node == NULL) {

/* Node does not exist, so create it */
node = (TrieNode *) malloc(sizeof(TrieNode));
memset(node, 0,sizeof(TrieNode));
if(node){
++node_memory;
//printf("node malloc memory count :- %d",node_memory);
}
// printf("\n created new node %x", node);

/* Link in to the trie */

*rover = node;
}

/* One more use of this node */

++node->use_count;

/* Current character */

c = *p;

/* Reached the end of string? If so, we're finished. */

if (c == '\0') {

/* Set the data at the node we have reached */

node->data = value;
break;
}

/* Advance to the next node in the chain */

rover = &node->next[c];
++p;
}
node->data = value;
}

here is the gdb o/p i tried to print the node but its not allocating memory giving null

(gdb) f 1
#1 0x08048984 in trie_insert (trie=0x8055028, key=0xbfef9338 "angelnympho.com\n", value=0xbfef9338) at trietest.c:123
123 memset(node, 0,sizeof(TrieNode));
(gdb) list
118 if (node == NULL) {
119
120
121 /* Node does not exist, so create it */
122 node = (TrieNode *) malloc(sizeof(TrieNode));
123 memset(node, 0,sizeof(TrieNode));
124 if(node){
125 ++node_memory;
126 //printf("node malloc memory count :- %d",node_memory);
127 }
(gdb) print node_memory
$1 = 581262
(gdb) print node
$2 = (TrieNode *) 0x0
(gdb)

NevemTeve · 08-10-2012, 02:37 AM

As your never check the return value of 'malloc', I suggest you use an 'emalloc' function instead that aborts when unsuccessful. Example:

Code:

void *emalloc (size_t size)
{
    void *p;
    char tmp [256];
    size_t tmpl;
 
    p = malloc (size);
    if (p) return p;
    fprintf (stderr, "*** Out of memory malloc(%lu)\n", (unsigned long)size);
    exit (1);
}

PS: please use tags [code] and [/code] around your code.