Question

我有一个实现B + Tree的代码。订单是3

问题是如果我在树中插入第三个值（叶子被拆分）它会在行中抛出分段错误

temp_pointers = (void**) malloc(order * sizeof(void *));

以下是leaf split

的完整代码

node * split_leaf_and_insert(node * root, node * leaf, char* key,
        record * pointer) {
    node * new_leaf = NULL;
    char ** temp_keys = NULL;
    void ** temp_pointers = NULL;
    int insertion_index, split, i, j;
    char*new_key;
    new_leaf = create_leaf();
    temp_keys = (char**) malloc(order * sizeof(char*));
    if (temp_keys == NULL) {
        exit(EXIT_FAILURE);
    }
    temp_pointers = (void**) malloc(order * sizeof(void *));
    if (temp_pointers == NULL) {
        exit(EXIT_FAILURE);
    }
    insertion_index = 0;
    while (insertion_index < order - 1 && leaf->keys[insertion_index] < key) {
        insertion_index++;
    }
    for (i = 0, j = 0; i < leaf->number_of_keys; i++, j++) {
        if (j == insertion_index) {
            j++;
        }
        temp_keys[j] = (char*) malloc(strlen(leaf->keys[i]) + 1);
        strcpy(temp_keys[j], leaf->keys[i]);
    }
    temp_keys[insertion_index] = (char*) malloc(strlen(key) + 1);
    strcpy(temp_keys[insertion_index], key);
    temp_pointers[insertion_index] = pointer;

    leaf->number_of_keys = 0;
    split = cut(order - 1);
    for (i = 0; i < split; i++) {
        leaf->pointers[i] = temp_pointers[i];
        leaf->keys[i] = (char*) malloc((strlen(temp_keys[i]) + 1));
        strcpy(leaf->keys[i], temp_keys[i]);
        leaf->number_of_keys++;
        for (i = split, j = 0; i < order; i++, j++) {
            new_leaf->pointers[j] = temp_pointers[i];
            new_leaf->keys[j] = (char*) malloc(strlen(temp_keys[i]) + 1);
            strcpy(new_leaf->keys[j], temp_keys[i]);
            new_leaf->number_of_keys++;
        }
        free(temp_pointers);
        free(temp_keys);
        new_leaf->pointers[order - 1] = leaf->pointers[order - 1];
        leaf->pointers[order - 1] = new_leaf;
        for (i = leaf->number_of_keys; i < order - 1; i++) {
            leaf->pointers[i] = NULL;
        }
        for (i = new_leaf->number_of_keys; i < order - 1; i++) {
            new_leaf->pointers[i] = NULL;
        }
        new_leaf->parent = leaf->parent;
        new_key = (char*) malloc(strlen(new_leaf->keys[0]) + 1);
        strcpy(new_key, new_leaf->keys[0]);
    }
    return insert_value_into_parent(root, leaf, new_key, new_leaf);
}

就像我说的前两个记录一样，但是第三个记录是

Use of uninitialised value of size 8 when use malloc in c

The stack trace
==1336== Use of uninitialised value of size 8
==1336==    at 0x4041F5: display (b-tree.c:754)
==1336==    by 0x40519C: main (main.c:54)
==1336==  Uninitialised value was created by a heap allocation
==1336==    at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1336==    by 0x4036D0: split_leaf_and_insert (b-tree.c:597)
==1336==    by 0x402E3C: insert_value (b-tree.c:477)
==1336==    by 0x4029B1: search (b-tree.c:396)
==1336==    by 0x404159: display (b-tree.c:739)
==1336==    by 0x40519C: main (main.c:54)
==1336== 
==1336== Invalid read of size 8
==1336==    at 0x4041F5: display (b-tree.c:754)
==1336==    by 0x40519C: main (main.c:54)
==1336==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
==1336== 
==1336==

下一个函数是调用上面的函数的插入函数

node * insert_value(node * root, char* key, record * rec) {
    node * leaf;
    if (root == NULL) {
        return create_new_tree(key, rec);
    }
    leaf = find_leaf(root, key);
    if (leaf->number_of_keys < order - 1) {
        leaf = insert_value_into_leaf(leaf, key, rec);
        return root;
    }
    return split_leaf_and_insert(root, leaf, key, rec);
}

有谁能解释一下发生了什么？

在c中使用malloc时使用大小为8的未初始化值

0 个答案: