c - malloc() 调用函数 - 段错误 : 11

Question

我是 C 语言初学者，刚刚尝试实现 makeRandomTree() 函数来随机创建二叉树。

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

我希望有人能帮助我 =)

这是源代码:

#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

树处理代码一般看起来没问题，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);

如果这棵树碰巧没有左 child 或右 child ，您可以尝试取消引用 NULL 指针。通过 if (tree->leftChild) ...

保护它