二叉树构造问题中的“分段错误：11”错误

Question

I was working on my C programing practice which needs me to construct a strictly binary tree with given postorder data in input file. My program first read the input data in inverted order into a linked list. And when I was trying to compile my tree-constructing function, the compiler showed this error:

Segmentation fault: 11

Can anybody help me with this problem? Thanks!

#include <string.h>
#include <stdlib.h>
#include "pa3.h"


static char* substr(const char *src, int m, int n);
static List_Node *insert_node(List_Node *tail, char* buffer);
static struct T_Node* newNode(char* string);

static char* substr(const char *src, int m, int n)
{
    int len = n - m;
    char *dest = (char*)malloc(sizeof(char) * (len + 1));

    for (int i = m; i < n && (*(src + i) != '\0'); i++)
    {
        *dest = *(src + i);
        dest++;
    }
    *dest = '\0';

    return dest - len;
}

static T_Node* newNode(char* string)
{
    T_Node* t_node = malloc(sizeof(*t_node));
  if (t_node == NULL)
  {
    printf("malloc failed");
    return NULL;
  }

  printf("malloc success");
  printf("string[0] is |%c|", string[0]);

    if(string[0] == '(')
  {
    char* left = substr(string, 1, 13);
    t_node->node->left_child = strtod(left, NULL);
    char* right = substr(string, 14, 12);
    t_node->node->right_child = strtod(right, NULL);
  }
  else
  {
    int l = (int)(string[0]);
    printf("label is %d", l);
    t_node->l_node->label = l;
    char* c = substr(string, 2, 12);
    t_node->l_node->cap = strtod(c, NULL);
  }

    t_node->left = t_node->right = NULL;

    return t_node;
}

T_Node* constructBST(List_Node* tail)
{
  printf("start newnode");
    T_Node *t_node = newNode(tail->string);
  printf("newnode succuess");

  if((tail->string)[0] != '(')
  {
    tail = tail->prev;////////////////
    return t_node;
  }
  tail = tail->prev;

    t_node->right = constructBST(tail);
    t_node->left = constructBST(tail);

    return t_node;
}

static List_Node *insert_node(List_Node *tail, char* buffer)
{
  List_Node *new = malloc(sizeof(*new));
  if (new == NULL)
  {
    return NULL;
  }

  *new = (List_Node){.string = buffer, .next = NULL};
  //printf("new is %s\n", new->string);

  if (tail != NULL)
  {
    tail->next = new;
    new->prev = tail;
  }
  return new;
}

List_Node* Load_Tree_From_Input(char* filename, double* rd, double* r, double* c)
{
  FILE* input_fptr = NULL;
  input_fptr = fopen(filename, "r");
  if (input_fptr == NULL)
  {
    printf("open failed\n");
    return NULL;
  }

  fscanf(input_fptr, "%le %le %le", rd, r, c);
  rewind(input_fptr);

  char bu[100];
  fgets(bu, 100, input_fptr);
  printf("stringend is %s", bu);

  List_Node* tail = NULL;
  while(feof(input_fptr) == 0)
  {
    //char* buffer = malloc(sizeof(char));
    char buffer[100];
    fgets(buffer, 50, input_fptr);
    printf("string is %s", buffer);
    tail = insert_node(tail, buffer);
  }

  //printf("FINAL string is %s", tail->string);

  fclose(input_fptr);
  return tail;
}


int main(int argc, char **argv)
{
  double rd = 0;
  double r = 0;
  double c = 0;

  if (argc == 2)
  {
    List_Node* tail = Load_Tree_From_Input(argv[1], &rd, &r, &c);
    puts(tail->string);
    //printf("FINAL string is |%s|", tail->string);
    List_Node test;
    T_Node* root = constructBST(&test);
    printf("tree planted\n");

    return EXIT_SUCCESS;
  }
  else
    printf("argument error\n");
    return EXIT_FAILURE;
}

#define __PA3_H__

typedef struct Node {
  double left_child;
  double right_child;
} Node;

typedef struct L_Node{
  int label;
  double cap;
} L_Node;

typedef struct T_Node
{
  Node *node;
  L_Node *l_node;
  struct T_Node *left;
  struct T_Node *right;
} T_Node;


typedef struct List_Node {
  struct List_Node *prev;
  char* string;
  struct List_Node *next;
} List_Node;

List_Node* Load_Tree_From_Input(char* filename, double* rd, double* r, double* c);
T_Node* constructBST(List_Node* tail);

#endif

Answer 1

you have a lot of memory errors, try to lunch your program with valgrind and correct it. use the -g3 flag in the compilation to get errors line