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麻烦。我尝试了几种不同的方式来定义它们，但似乎无法摆脱错误。

我可能也有代码的其他问题的财富，但我实际上无法通过运行我认为的代码找到它们而无法修复这些问题。这就是为什么我需要首先解决这个问题。

下面是完整的代码：

#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(); 
} 

这里有错误，我得到：

|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

正如在评论中发现，你的问题是从你的结构定义：

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

您在typedef结束之前调用struct node。只需struct node由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，并且你试图将一行分配给一个char。如果你想创建一个十字节长的字符数组，只是把它定义是这样的：

char C[10]; 

顺便说一下，如果你想打印的printf同一个字符串，它与%s，不&s。