C：clang在Mac上提供了段错误

Question

以下是将已排序的数组转换为BST的程序。我能够使用在线C编译器编译和执行程序。当我在本地系统上尝试编译时，它会抛出一个分段错误。

SortedArraytoBST.c

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

// Structure of the node
struct TNode
{   
    int data;
    struct TNode* left;
    struct TNode* right;
};

struct TNode* newNode(int data);

// Function that converts array to BST
struct TNode* SortedArrayToBST(int arr[], int start, int end)
{
    if(start > end)
    {
        return NULL;
    }
    if(start == end)
    {
        struct TNode* newnode2 = newNode(arr[start]);
        return newnode2;
    }
    int mid = (start+end)/2;
    struct TNode* newnode = newNode(arr[mid]);
    newnode->left = SortedArrayToBST(arr, start, mid-1);
    newnode->right = SortedArrayToBST(arr, mid+1, end);
    return newnode;
}

//NewNode Creation
struct TNode* newNode(int data)
{
    struct TNode* node = (struct TNode*)malloc(sizeof(struct TNode*));
    node->data = data;
    node->left = NULL;
    node->right = NULL;
    return node;
}

// Print the tree in preorder
void preorder(struct TNode* node)
{
    if( node == NULL) return;
    printf("%d\n", node->data);
    preorder(node->left);
    preorder(node->right);
}

// Array to BST
int main()
{
    int arr[]={1,2,3};
    int size = sizeof(arr)/sizeof(arr[0]);
    struct TNode* root = SortedArrayToBST(arr, 0, size-1);
    preorder(root);
    return 0;
}

用于编译程序的命令

$ gcc -o SortedArraytoBST SortedArraytoBST.c
$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.2.0
Thread model: posix
$

我本地Mac上的程序输出

    2
    -398445936
    Segmentation fault: 11

http://code.geeksforgeeks.org/

上的节目输出

    2
    1
    3

Answer 1

第36行，您的分配错误导致堆缓冲区溢出。

你应该写：

struct TNode* node = (struct TNode*)malloc(sizeof(struct TNode));

代替：

struct TNode* node = (struct TNode*)malloc(sizeof(struct TNode*));

如何调试

如果您获得gcc 4.8或更高版本，则可以运行地址清理程序：

gcc -fsanitize=address -fno-omit-frame-pointer -g myprogram.c -o myprogram

我得到了什么：

=================================================================
==22711==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000eff8 at pc 0x000000400bbb bp 0x7ffea7e3c630 sp 0x7ffea7e3c628
WRITE of size 8 at 0x60200000eff8 thread T0
    #0 0x400bba in newNode /home/jyvet/TMP/myprogram.c:38
    #1 0x400aac in SortedArrayToBST /home/jyvet/TMP/myprogram.c:27
    #2 0x400d75 in main /home/jyvet/TMP/myprogram.c:57
    #3 0x7f68db2c7b44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)
    #4 0x4008e8  (/home/jyvet/TMP/myprogram+0x4008e8)

0x60200000eff8 is located 0 bytes to the right of 8-byte region [0x60200000eff0,0x60200000eff8)
allocated by thread T0 here:
    #0 0x7f68db6e337a in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9437a)
    #1 0x400b59 in newNode /home/jyvet/TMP/myprogram.c:36
    #2 0x400aac in SortedArrayToBST /home/jyvet/TMP/myprogram.c:27
    #3 0x400d75 in main /home/jyvet/TMP/myprogram.c:57
    #4 0x7f68db2c7b44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b44)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/jyvet/TMP/myprogram.c:38 newNode