Thread: Help.. segfault error

I didnt get much help last time I posted this...
please help..

Im having trouble finding what my problem is..

Im writing a binary tree library and when I run this test program: (cannot be changed)

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "bintree.h"

void print_name(char *key, void *value){
   printf("%s\n", key);
}

main(int argc, char *argv[]) {
  if (argc <= 1) {
    fprintf(stderr, "usage: bst_test name1 name2 ... namek\n");
    exit(1);
  }
  void *tree = create_tree();
  int i;

  // test inserts
  for (i = 1; i < argc; i++) {
     tree_insert(strdup(argv[i]), (void *)1, tree);
  }

  // test print tree
  print_tree(tree, print_name);

  // test finds
  for (i = 0; i < argc; i++) {
    if (tree_find(argv[i], tree) == 0)
      printf("%s not in data set\n", argv[i]);
  }
}

I get these errors:

Code:

(gdb) bt
#0  0xb7edfd2a in strcmp () from /lib/tls/i686/cmov/libc.so.6
#1  0x0804853e in tree_insert (key=0x804a030 "name", value=0x1,
    tree=0x804a008) at bintree.c:33
#2  0x0804878d in main (argc=3, argv=0xbfe13134) at test.c:22

Here is the library im writing:

Code:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>


typedef struct _node{
    struct _node *children;
    struct _node *next;
    char *name;
    int space;
    int x; //x coordinate
    int y; //y coordinate
} NODE;

typedef struct _bnode{
    char *name;
    struct _node family_node;
    struct _bnode *left;
    struct _bnode *right;
} BNODE;

BNODE *tree_insert(char *key, void *value, void *tree){
    BNODE *root = (BNODE *)tree;
    if(root == 0){
        root = (BNODE *)malloc(sizeof(BNODE));
        if(root != NULL)
        {
            root->name = strdup(key);
            root->left = NULL;
            root->right = NULL;
        }
    }else{
        if(strcmp(key, root->name) < 0){   <--- line 33
            root->left = tree_insert(key, value, root->left);
        }else if(strcmp(key, root->name) > 0){
            root->right = tree_insert(key, value, root->right);
        }else if(strcmp(key, root->name) == 0){
	    root->name = strdup(key);
        }
    }

    return root;
}


BNODE *tree_find(char *key, void *tree){
    BNODE *root = (BNODE *)tree;
    if(root == 0){
        return 0;
    }
    if(strcmp(key, root->name) < 0){
        return tree_find(key, root->left);
    }else if(strcmp(key, root->name) > 0){
        return tree_find(key, root->right);
    }else{
        return root;
    }
}


void *create_tree(){
    BNODE *new_tree = (BNODE *)malloc(sizeof(BNODE));
    new_tree->left = NULL;
    new_tree->right = NULL;
    return new_tree;

}

void print_tree(void *tree, void(*print_fct)(char *key, void *value)){
    BNODE *current = (BNODE *)tree;

    if(current == NULL || print_fct == NULL){
        return;
    }else{
        print_tree(current->left, print_fct);

        print_fct(current->name, (void *)current->family_node.space);

        print_tree(current->right, print_fct);
    }

}

Originally Posted by Salem

Does your create_tree() initialise all the pointers, and all the members of a BNODE?

I think so.. well i want it to.. is it not?

There are four members; you set two. What do you think?

Originally Posted by tabstop

There are four members; you set two. What do you think?

Oh ya thats all I want.. I set name in my insert function..

I just saw that last post by itcbitc.. lol.. I swear i didnt see it before..

that fixed it..

I get it now lol

You have not set any value to root->name before using it within strcmp in your library function tree_insert, which is invoked in main.c after create_tree, It results an access violation error.

Don't use strdup to duplicate string since it has been announced as obsoleted (It allocates memory inside by using malloc, and you have never free it).

Root cause of the problem is that you are allocating the root node in two places ie create_tree() and in this piece of code from tree_insert().

Code:

BNODE *tree_insert(char *key, void *value, void *tree){
    BNODE *root = (BNODE *)tree;
    if(root == 0){
        root = (BNODE *)malloc(sizeof(BNODE));
        if(root != NULL)
        {
            root->name = strdup(key);
            root->left = NULL;
            root->right = NULL;
        }

You need either one or the other and to be consistent keep the one from tree_insert(), after all adding the root node is the same as adding any another node.

Originally Posted by itCbitC

Root cause of the problem is that you are allocating the root node in two places ie create_tree() and in this piece of code from tree_insert().

Code:

BNODE *tree_insert(char *key, void *value, void *tree){
    BNODE *root = (BNODE *)tree;
    if(root == 0){
        root = (BNODE *)malloc(sizeof(BNODE));
        if(root != NULL)
        {
            root->name = strdup(key);
            root->left = NULL;
            root->right = NULL;
        }

You need either one or the other and to be consistent keep the one from tree_insert(), after all adding the root node is the same as adding any another node.

I fixed it thankyou ..

Im not getting the segfault anymore but Im getting this output
i wanted it to print in alphabetical order.. so thats right at least..

unix> ./program hey there billy joe joe
<-- Im getting this extra space?
billy
hey
joe
there
./test_option1 not in data set <-- and its taking on the first argument for some reason..
unix>

Originally Posted by itCbitC

see the code section under // test finds and you will know why its printing the program name ie argv[0]...and post the source of print_fct().

is there anyway to change my bintree library instead of that code? I cant edit that ..