我似乎找不到内存分配出错的地方。所有功能均正常运行，但程序在执行过程中会随机崩溃。我知道错误在于我如何为链表分配内存，但是我似乎无法弄清楚哪一部分是错误的。
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <cstring>
using namespace std;
void menu_function(void);
void command_execute(string command, string name1, string name2);
int hash_function(string str);
void insert_into_hashtable(int ascii_total, string name);
void add_friendship(int ascii_key, string name);
void print_friendships(int aascii_key);
void check_friendship(int ascii_key, string name);
void remove_friendship(int ascii_key, string name);
#define SIZE 125
struct friend_list {
string name = "";
struct friend_list * next;
};
typedef struct friend_list list;
struct user {
string name;
int key;
friend_list * FriendList;
};
struct user * hashArray[SIZE];
int main(int argc,
const char * argv[]) {
menu_function();
return 0;
}
void menu_function() {
char user_input[100]; //this could limit the size of input
string command;
string name1 = "\0";
string name2 = "\0";;
char * token; ** strong text **
int inputsize = 100;
int i = 0;
char delimit[] = " \t\r\n\v\f";
while (1) {
printf("\nP <Name> to create a person\n");
printf("F <Name> <Name> record friendship\n");
printf("U <Name> <Name> terminate friendship\n");
printf("L <Name> print out friends of a specified person\n");
printf("Q <Name> <Name> check friendship status of two people\n");
printf("X - terminate the progarm\n");
// Determine user input and
fgets(user_input, inputsize, stdin);
//getline(&input, &inputsize, stdin);//takes in user input;
//printf("input: %s", user_input);
//parsing the string for the data within
token = strtok(user_input, delimit);
i = 0;
while (token != NULL) {
if (i == 0) {
command = token;
//cout<< command<<endl;
}
if (i == 1) {
name1 = token;
// cout<< name1<<":"<<endl;
}
if (i == 2) {
name2 = token;
// cout<< name2<<":"<<endl;
name1 = name1 + "\n";
}
token = strtok(NULL, " ");
i++;
}
command_execute(command, name1, name2);
command = '\0';
name1 = '\0';
name2 = '\0';
}
}
void command_execute(string command, string name1, string name2) {
//cout<<"command is: "<<command<<endl;
switch (command[0]) {
case 'P': //Create record of the person
insert_into_hashtable(hash_function(name1), name1);
break;
case 'F': //Record friendship
add_friendship(hash_function(name1), name2);
add_friendship(hash_function(name2), name1);
break;
case 'U': //Terminate Friendship
remove_friendship(hash_function(name1), name2);
remove_friendship(hash_function(name2), name1);
break;
case 'L': //Print out the persons Friends
print_friendships(hash_function(name1));
break;
case 'Q': //Check on friendship
check_friendship(hash_function(name1), name2);
break;
case 'X': //Exit the program **** COMPLETED
exit(1);
break;
default:
cout << "Error occured based on your command please try again" << endl;
break;
}
}
int hash_function(string string) {
//going to use the ASCI value of the name with different weights per array position to hash the names
int ascii_key = 0;
int ascii_total = 0;
// cout<< string.length()<< endl;
//cout<< string<< endl;
for (int i = 0; i < string.length() - 1; i++) {
ascii_total = (int) string[i] * (i * 3 + 1);
// cout<< string[i]<< endl;
}
ascii_key = ascii_total % SIZE;
//deals with colisions through open hashing
while (hashArray[ascii_key] != NULL && strcmp(hashArray[ascii_key] - > name.c_str(), string.c_str())) { //strcmp(hashArray[ascii_key]->name.c_str(), string.c_str())
//hashArray[ascii_key] != NULL ||
ascii_key++;
}
// ****** decide size of the hash table and then finished hashing function. Usually hash time is gonna be half full
cout << ascii_key << endl;
return ascii_key;
}
void insert_into_hashtable(int ascii_key, string name) {
int k = 0;
//get the hash key
user * item = (user * ) malloc(sizeof(struct user));
item - > name = name;
item - > key = ascii_key;
item - > FriendList = NULL;
cout << ascii_key << endl;
//collisions resolved by linear probing
//store the user in the table
hashArray[ascii_key] = item;
k++;
//free(item);
}
void add_friendship(int ascii_key, string name) {
//gonna have to check for valid input on users
list * add = (list * ) malloc(sizeof(struct friend_list));
add - > name = name;
add - > next = NULL;
if (ascii_key == 13) {
ascii_key = ascii_key;
}
/* if( hashArray[ascii_key]->FriendList->next == NULL )
{
cout<<hashArray[ascii_key]->FriendList<<endl;
hashArray[ascii_key]->FriendList = temp;
}
else*/
{
add - > next = hashArray[ascii_key] - > FriendList;
hashArray[ascii_key] - > FriendList = add;
}
free(add);
}
void print_friendships(int ascii_key) {
friend_list * temp = (friend_list * ) malloc(sizeof(friend_list));
temp = hashArray[ascii_key] - > FriendList;
while (temp != NULL) {
cout << temp - > name << endl;
if (temp - > next == NULL) {
free(temp);
return;
}
temp = temp - > next;
}
//free(temp);
}
void check_friendship(int ascii_key, string name) {
list * temp = (list * ) malloc(sizeof(struct friend_list));
temp = hashArray[ascii_key] - > FriendList;
while (temp != NULL) {
if (strcmp(temp - > name.c_str(), name.c_str()) == 0) {
cout << "Friendship exist" << endl;
return;
}
temp = temp - > next;
}
cout << "No Record of Friendship" << endl;
free(temp);
}
//need to finish
void remove_friendship(int ascii_key, string name) {
list * temp = (list * ) malloc(sizeof(struct friend_list));
list * prev = (list * ) malloc(sizeof(struct friend_list));
temp = hashArray[ascii_key] - > FriendList;
if (temp != NULL && temp - > name == name) {
hashArray[ascii_key] - > FriendList = temp - > next; // Changed head
// free old head
return;
}
//not the head
while (temp != NULL && temp - > name != name) {
prev = temp;
temp = temp - > next;
}
if (temp == NULL) return;
// Unlink the node from linked list
prev - > next = temp - > next;
free(temp);
free(prev);
}
答案 0 :(得分：2)
可能有很多错误，但这是一个很大的错误
resources:
Resources:
RestApi :
Type : AWS::ApiGateway::RestApi
Properties :
Body : ${file(./swagger.yaml)}
LoginApiToInvokeLambda:
Type: AWS::Lambda::Permission
DependsOn: LoginLambdaFunction
Properties:
FunctionName: xxx-ext-api-dev-login
Action: lambda:InvokeFunction
Principal: apigateway.amazonaws.com
RequestValidatorAll:
Type: AWS::ApiGateway::RequestValidator
Properties:
Name: all
RestApiId:
Ref: RestApi
ValidateRequestBody: true
ValidateRequestParameters: true
应该是
user *item = (user*) malloc(sizeof(struct user));
在C ++中，您应该始终使用 user *item = new user;
。 new和new之间的区别在于malloc不调用任何构造函数。因此，不会在malloc对象中调用user的构造函数。因此，每当您尝试使用string name时，都会有不确定的行为（即潜在的崩溃）。并且正如评论中所述，出于基本相同的原因，您还应该使用name而不是delete。
多看一些代码，发现了很多与指针相关的错误。例如呢
free稍微忘记一下malloc和new，只需看一下上面的代码即可。您有一个指针list* temp = (list*)malloc(sizeof(struct friend_list));
temp = hashArray[ascii_key]->FriendList;
，它指向一些已分配的内存。然后，您丢弃该内存，而将temp指向temp。如果不使用内存，分配内存有什么意义？然后，您可以通过在函数末尾释放内存来加重错误。
hashArray[ascii_key]->FriendList，但是free(temp);
不再指向分配的内存（因为您改为将其指向朋友列表）。很明显，您确实还不了解指针和内存分配。
这是您应该编写该函数的方式
temp请参阅完全没有分配。我想您脑子里有某种规则，无论哪里有指针，我都必须分配一些内存。事实并非如此，分配是关于创建新对象的。 void check_friendship( int ascii_key, string name)
{
list* temp = hashArray[ascii_key]->FriendList;
while( temp != NULL)
{
if(strcmp(temp->name.c_str(), name.c_str()) == 0)
{
cout<<"Friendship exist"<<endl;
return;
}
temp = temp->next;
}
cout<<"No Record of Friendship"<<endl;
}
不会创建任何新对象（只会检查现有对象），因此不需要分配或释放任何对象。
check_friendship有一个相同的问题，因为它正在删除一个友谊，因此它应该remove_friendship一个对象（友谊被删除），但是没有理由为其分配任何东西。
delete具有相同的错误，但相反。 add_friendship应该为要添加的友谊分配一个新对象，您可以这样做，但是然后尝试在函数末尾释放该对象。您正在某种总括规则下操作，必须分配每个指针变量然后释放它们，而不是从逻辑上考虑每个函数需要创建或破坏的对象。