取消引用指向不完整类型的指针（基数树）

Question

我的结构定义遇到了很大的问题。我尝试了几种不同的方法来定义它们，但似乎无法消除错误。

我的代码可能还有很多其他问题，但如果不通过运行我认为的代码找到它们，我实际上无法解决这些问题。这就是为什么我需要先解决这个问题。

完整代码如下：

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

typedef int bool;
enum { false, true };

typedef struct radixNode {
    bool active;
    struct node * pnt;
    struct node * l;
    struct node * r;
} node;

void insert(node *root, char * B) {

    // digit is zero so we go left
    if (B[0] == 0) {

        // left child doesn't exist, create it
        if (root->l == NULL) {

            root->l = malloc(sizeof(node));

            /* if the next index in the string does NOT contain a 1 or 0,
            the current index is the last index and the node is activated */
            if (B[1] == 1 || B[1] == 0)
                root->l->active = false;
            else
                root->l->active = true;

            root->l->pnt = root;
            root->l->l = NULL;
            root->l->r = NULL;
            insert(root->l,B++); // B++ removes the first digit of the string
        }

        // left child exists, traverse
        else {
            insert(root->l,B++);
        }
    }

    // digit is one, go right
    else {

        // right child doesn't exist, create it
        if (root->r == NULL) {

            root->r = malloc(sizeof(node));

            /* if the next index in the string does NOT contain a 1 or 0,
            the current index is the last index and the node is activated */
            if (B[1] == 1 || B[1] == 0)
                root->r->active = false;
            else
                root->r->active = true;

            root->r->pnt = root;
            root->r->l = NULL;
            root->r->r = NULL;
            insert(root->r,B++);
        }

        // left child exists, traverse
        else {
            insert(root->r,B++);
        }
    }
}

node * printTreeMin(node *root) {

    char * C[10];

    /* goes left until it can't, appends 0 to string
    till it can't. if node is active, print the string */
    while (root->l != NULL) {

        C[strlen(C)] = '0';

        if (root->active)
            printf("&s\n",C);

        root = root->l;
    }

    return root;
}

// prints the next smallest binary number in the tree, returns the node it printed
node * printNextSmallest(node * root) {

    char * C[10];

    // if right child exists, go there and find lowest node (after if same deal as printTreeMin() )
    if (root->r != NULL) {

        C[strlen(C)] = '1';
        if (root->active)
            printf("&s\n",C);

        root = root->r;

        while (root->l != NULL) {

            C[strlen(C)] = '0';
            if (root->active)
                printf("&s\n",C);

            root = root->l;
        }

        return root;
    }

    node * temp = root->pnt;

    while (temp != NULL && root == temp->r) {

        root = temp;
        temp = temp->pnt;
    }

    return temp;
}

void printRadixTree(node *root) {

    root = printTreeMin(root);

    while (printNextSmallest(root) != NULL)
        root = printNextSmallest(root);
}

void test() {

    node * tree = malloc(sizeof(node));
    tree->l = NULL;
    tree->r = NULL;

    // a)
    insert(tree,"101000");
    insert(tree,"10100");
    insert(tree,"10110");
    insert(tree,"101");
    insert(tree,"1111");

    // b)
    printRadixTree(tree);

}

int main() {
    test();
}

这是我得到的错误：

|In function 'insert':|
30|error: dereferencing pointer to incomplete type|
32|error: dereferencing pointer to incomplete type|
34|error: dereferencing pointer to incomplete type|
35|error: dereferencing pointer to incomplete type|
36|error: dereferencing pointer to incomplete type|
37|warning: passing argument 1 of 'insert' from incompatible pointer type [enabled by default]|
17|note: expected 'struct node *' but argument is of type 'struct node *'|
42|warning: passing argument 1 of 'insert' from incompatible pointer type [enabled by default]|
17|note: expected 'struct node *' but argument is of type 'struct node *'|
57|error: dereferencing pointer to incomplete type|
59|error: dereferencing pointer to incomplete type|
61|error: dereferencing pointer to incomplete type|
62|error: dereferencing pointer to incomplete type|
63|error: dereferencing pointer to incomplete type|
64|warning: passing argument 1 of 'insert' from incompatible pointer type [enabled by default]|
17|note: expected 'struct node *' but argument is of type 'struct node *'|
69|warning: passing argument 1 of 'insert' from incompatible pointer type [enabled by default]|
17|note: expected 'struct node *' but argument is of type 'struct node *'|

|In function 'printTreeMin':|
82|warning: passing argument 1 of 'strlen' from incompatible pointer type [enabled by default]|
49|note: expected 'const char *' but argument is of type 'char **'|
82|warning: assignment makes pointer from integer without a cast [enabled by default]|
87|warning: assignment from incompatible pointer type [enabled by default]|

|In function 'printNextSmallest':|
101|warning: passing argument 1 of 'strlen' from incompatible pointer type [enabled by default]|
49|note: expected 'const char *' but argument is of type 'char **'|
101|warning: assignment makes pointer from integer without a cast [enabled by default]|
105|warning: assignment from incompatible pointer type [enabled by default]|
109|warning: passing argument 1 of 'strlen' from incompatible pointer type [enabled by default]|
49|note: expected 'const char *' but argument is of type 'char **'|
109|warning: assignment makes pointer from integer without a cast [enabled by default]|
113|warning: assignment from incompatible pointer type [enabled by default]|
119|warning: initialization from incompatible pointer type [enabled by default]|
121|warning: comparison of distinct pointer types lacks a cast [enabled by default]|
124|warning: assignment from incompatible pointer type [enabled by default]|

||=== Build failed: 10 error(s), 16 warning(s) (0 minute(s), 0 second(s)) ===|

Answer 1

如评论中所见，您的问题出在您的结构定义上：

typedef struct radixNode {
    bool active;
    struct node * pnt;
    struct node * l;
    struct node * r;
} node;

您在 typedef 结束前调用 struct node。只需将 struct node 替换为 struct radixNode.

对于你的第二个问题，这是因为你的变量 C 是一个指针数组，而不是一个字符数组，而你正试图将一行分配为一个字符。如果要创建一个十字节长的字符数组，只需这样定义它：

char C[10];

顺便说一句，如果你想用 printf 打印一个字符串，它是 %s，而不是 &s。

取消引用指向不完整类型的指针（基数树）

dereferencing pointer to incomplete type (radix tree)

c

struct

dereference

radix-tree