c - Original node changes when inserting nodes into binary tree -

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i'm trying make binary tree using recursive insert function root node seems keep changing(if didn't, printf should give same output in code below). thoughts on how fix this? 

typedef struct tnode{      char name[30];     int value;      struct tnode *left;     struct tnode *right;  } tnode;   tnode *insert(tnode *node, char *name, int value){       if(node==null){          tnode *temp = malloc(sizeof(struct tnode));          sprintf(temp->name,"%s",name);         temp->value = value;          temp->left = null;         temp->right = null;          return temp;      }      else if(strcmp(name,node->name)<0)     {         node->left = insert(node->left, name, value);        }      else if(strcmp(name,node->name)>0)     {         node->right = insert(node->right, name, value);     }        else{         printf("something went wrong\n");     }     }   int main(){      tnode *root = null;      root = insert(root,"george",11);     root = insert(root,"dick",12);     printf("%s\n",root->name);       root = insert(root,"walter",13);     root = insert(root,"harry",13);     printf("%s\n",root->name);       root = insert(root,"zink",40);     printf("%s\n",root->name);     }

ok, we've figured out together. insert() declared 

tnode *insert(...)

so allways needs return pointer tnode, there cases in if-clause lead execution branch doesn't return anything. guess it's undefined return value.

since insert() operates recursively passing call "if you're leaf, put value here , return yourself", need handle case "and if you're not, ... and return ...". imagine have large tree , insert value, root passes call down binary structure until correct position found. final call (where recursion ends) return *tnode leaf previous call can correctly set node->left = insert(...);, there still "open" calls on stack (since it's recursion) needs closed, i.e. function terminates , every node writes node->left or node->right. if don't return anything, there might arbitrary values break data structure , lead undefined behavior.

so, solution add return node; @ end recursive calls can finalized leaving "passing" nodes between root , new leaf unchanged.


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