c - 解析读入文件并将其存储在二叉树中

Question

当我尝试将节点插入二叉树时，出现段错误。我用 gdb 运行程序，这是我发现的有关段错误的信息，但我真的不知道在插入和创建函数中要更改什么。感谢您提前提供的帮助。

Program received signal SIGSEGV, Segmentation fault.
__strcmp_sse42 () at ../sysdeps/x86_64/multiarch/strcmp.S:260
260     movdqu  (%rsi), %xmm2
(gdb) where
#0  __strcmp_sse42 () at ../sysdeps/x86_64/multiarch/strcmp.S:260
#1  0x0000000000400a42 in insert_into_commands_tree (node=0x7fffffffe0b0, 
data=0x602270) at lab8.c:116
#2  0x00000000004009d7 in create_commands_tree (commands=0x7fffffffe0b0, 
file=0x7fffffffe4a1 "commands.dat") at lab8.c:104
#3  0x0000000000400835 in main (argc=2, argv=0x7fffffffe1b8) at lab8.c:48

我的程序所做的是读取文本文件并解析字符串，然后将它们存储到二叉树中。然后用户输入命令，我搜索树并查看该命令是否在树中列出。我将发布我的完整代码，以便大家都可以看到它，然后发布我读入的文件和示例输出，希望有人可以帮助我解决此段错误错误。预先非常感谢。我的老师也为我们提供了 main 和 tokenizer 函数。

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

#define COMMAND_NAME_LEN 50
#define MAX_SPLIT_SIZE 50
#define MAX_BUFF_SIZE 50

typedef struct Command_ {
    char name[COMMAND_NAME_LEN];
    int expected_param_count;
    struct Command_ *left;
    struct Command_ *right;
}Command;


typedef struct StringArray_ {
    char **strings;
    int size;
}StringArray;

StringArray* tokenizer (char *string, const char* delimiters);
void free_string_array(StringArray *sr);
void create_commands_tree(Command **commands, const char *file);
void insert_into_commands_tree(Command** node, char** data);
Command* get_command(Command *node, const char *command);
Command* create_command(char **data);
void destroy_commands_tree(Command* node);
void display_commands(Command *node);


int main (int argc, char *argv[]) {

    if (argc < 2) {
            printf("%s is missing commands.dat\n", argv[0]);
            return 0;
    }


    Command* options = NULL;
    create_commands_tree(&options,argv[1]);
    int checking = 1;

    char input_buffer[MAX_BUFF_SIZE];

    do {
            printf("Command: ");
            fgets(input_buffer,MAX_BUFF_SIZE,stdin);
            StringArray* parsed_input = tokenizer(input_buffer," \n");
            Command* c = get_command(options,parsed_input->strings[0]);

            if( c && parsed_input->size == c->expected_param_count) {
                    if (strcmp(c->name, "quit") == 0){
                                    checking = 0;
                    }
                    printf("Valid command used\n");
            }
            else {
                    printf("Invalid command, please try again\n");
            }
            free_string_array(parsed_input);

    }while (checking);

    destroy_commands_tree(options);

}


void create_commands_tree(Command **commands, const char *file) {

    FILE *input;
    input = fopen(file, "r");
    char strings[100];
    StringArray *temp2;

    while(fgets(strings,100,input)){

            temp2 = tokenizer(strings, "\n");
            insert_into_commands_tree(commands,temp2->strings);
    }
}

void insert_into_commands_tree(Command** node, char** data) {

    if(*node == NULL){
            *node = create_command(data);
    }
    else if( *node != NULL){
            if(strcmp(data[0],(*node)->name) < 0)
                    insert_into_commands_tree(&(*node)->left,data);
            else if(strcmp(data[0], (*node)->name) > 0)
                    insert_into_commands_tree(&(*node)->right,data);
    }


}

Command* create_command(char **data) {

    Command* new_;
    new_ = (Command*)malloc(sizeof(Command));
    strncpy(new_->name, data[0], COMMAND_NAME_LEN);
    new_->expected_param_count = atoi(data[1]);
    new_->right = NULL;
    new_->left = NULL;


    return new_;

}

Command* get_command(Command *node, const char *command) {

    Command *temp = node;
    int compare;

    if(temp){
            compare = strcmp(node->name, command);
            if(compare == 0){
                    return temp;
            }
            else if(compare < 0){
                    return (get_command(node->right, command));
            }
            else{
                    if(compare > 0){
                            return (get_command(node->left, command));
            }}

    }
   return temp;
}

void destroy_commands_tree(Command* node) {

    if( node == NULL){
            return;
            }

    destroy_commands_tree(node->left);
    destroy_commands_tree(node->right);
    free(node);

}
void display_commands(Command *node) {


            printf("\npickup <item>");
            printf("\nhelp ");
            printf("\nquit ");
            printf("\nload <file>\n\n");

}
 StringArray* tokenizer (char *string, const char* delimiters){

    StringArray* sr = malloc(sizeof(StringArray));
    sr->strings = malloc(MAX_SPLIT_SIZE * sizeof(char *));

    size_t len;
    char* hold;

    (sr->strings)[0] = malloc(MAX_BUFF_SIZE * sizeof(char));
    hold = strtok(string, delimiters);
    int i;
    for(i = 1; i < MAX_SPLIT_SIZE; i++){

            hold = strtok(NULL, delimiters);
            if(hold == NULL){
                    sr->size = i + 1;
                    break;
            }
            (sr->strings)[i] = malloc(MAX_BUFF_SIZE * sizeof(char));
            strcpy((sr->strings)[i], hold);
    }
    return sr;
}

void free_string_array(StringArray *sr) {

     int i;
    for(i = 0; i < sr->size; ++i){
             free(sr->strings[i]);
    }
            free(sr->strings);
            free(sr);
}

这是给出的示例输出:

]$ ./a.out commands.dat 
Command: pickup 
Invalid command, please try again 
Command: pickup ball 
Valid command used 
Command: quit 1 
Invalid command, please try again 
Command: load 
Invalid command, please try again 
Command: load bak.sav 
Valid command used 
Command: help
Valid command used
Command: help 2 
Invalid command, please try again 
Command: quit 
Valid command used 

我们读入的文件如下:

pickup,2
help,1
quit,1
load,2

Answer 1

此代码有几个问题:

在函数insert_into_commands_tree

中

就像上面评论中所说，条件应该是if (*node == NULL)。这可能是导致段错误的原因。

此外，if ... else if 结构在这里有点多余，因为它是一个真/假条件。您可以简单地使用:

void insert_into_commands_tree(Command** node, char** data) {

    if(*node == NULL) {
        *node = create_command(data);
    }
    else {
        if(strcmp(data[0],(*node)->name) < 0)
                insert_into_commands_tree(&(*node)->left,data);
        else if(strcmp(data[0], (*node)->name) > 0)
                insert_into_commands_tree(&(*node)->right,data);
    }
}

(但这只是一个小细节)

在函数create_commands_tree

中

您在这里所做的是使用 fgets 读取输入文件的一行，并用标记 "\n" 分隔该行，这是无用的(因为 fgets 已经分隔了行)。我想你的意思是:

temp2 = tokenizer(strings, ",");

在函数分词器

中

这个函数的输出不是它应该的。这里的主要问题是您没有将第一个 token 复制到 StringArray 中。下面是一个有效的(有点简化的)tokenizer 函数:

StringArray* tokenizer (char *string, const char* delimiters)
{
    StringArray* sr = malloc(sizeof(StringArray));
    sr->strings = malloc(MAX_SPLIT_SIZE * sizeof(char *));

    char* hold;
    int i = 0;

    hold = strtok(string, delimiters);
    while ((hold != NULL) && (i < MAX_SPLIT_SIZE))
    {
        (sr->strings)[i] = malloc(MAX_BUFF_SIZE * sizeof(char));
        strncpy((sr->strings)[i], hold, MAX_SPLIT_SIZE);
        i++;
        hold = strtok(NULL, delimiters);
    }

    sr->size = i;
    return sr;
}

通过这些修改，您的代码似乎可以达到您的预期。