malloc() 函数调用 - 分段错误：11

Question

我是一名 C 初学者，刚刚尝试实现一个 makeRandomTree() 函数来随机创建一棵二叉树。

虽然有时编译成功（并非总是如此！）但程序在运行时退出并出现错误“Segmentation fault: 11”。我认为错误位于 makeRandomNode() 函数中，其中包含 malloc() 的动态内存分配。不幸的是，我还没有找到错误。

希望有人能帮助我=)

这里是源代码：

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

#define NUMBER_OF_NODES 10
#define RANDOM_NUMBER_MAX 99

struct node {
    int nodeValue;
    struct node *parentNode;
    struct node *leftChild;
    struct node *rightChild;
};

typedef struct node node;

node* makeRandomNode(unsigned int *randomSeed) {
    //random number in the range [0;RANDOM_NUMBER_MAX]
    int random = (rand_r(randomSeed) % (RANDOM_NUMBER_MAX + 1));

    node *newNode = (node *) malloc(sizeof(node));

    newNode->nodeValue = random;
    newNode->parentNode = NULL;
    newNode->leftChild = NULL;
    newNode->rightChild = NULL;

    return newNode;
}

void insertNode(node *root, node *newNode) {
    if (newNode->nodeValue <= root->nodeValue) {
        if (root->leftChild == NULL) {
            root->leftChild = newNode;
            newNode->parentNode = root;
        }
        else {
            insertNode(root->leftChild, newNode);
        }
    }
    else {
        if (root->rightChild == NULL) {
            root->rightChild = newNode;
            newNode->parentNode = root;
        }
        else {
            insertNode(root->rightChild, newNode);
        }
    }
}

node* makeRandomTree(int numberOfNodes) {
    int i;
    unsigned int randomSeed;
    node *root;
    node *newNode;

    randomSeed = time(NULL);
    root = makeRandomNode(&randomSeed);

    for (i = 1; i < numberOfNodes; i++) {
        newNode = makeRandomNode(&randomSeed);  
        insertNode(root, newNode);
    }

    return root;
}

int main(int argc, char *argv[]) {
    node *tree = makeRandomTree(NUMBER_OF_NODES);

    printf("A random-binary-tree with %i nodes was created successfully!!!\n", NUMBER_OF_NODES);
    printf("'NodeValue' of root is %i\n", tree->nodeValue);
    printf("'NodeValue' of left child of root is %i\n", tree->leftChild->nodeValue);
    printf("'NodeValue' of right child of root is %i\n", tree->rightChild->nodeValue);
    printf("etc.\n");
}

Answer 1

一般来说，树处理代码看起来没问题，但这可能是个问题：

printf("'NodeValue' of left child of root is %i\n", tree->leftChild->nodeValue);
printf("'NodeValue' of right child of root is %i\n", tree->rightChild->nodeValue);

如果碰巧这棵树没有左子或右子，您尝试取消引用NULL-指针。 由if (tree->leftChild) ...保护它