打印结构的结构数组会导致意外的执行错误？

Question

对于这个结构定义，我初始化了所有的结构，然后用 printstruct() 打印它们的内容；但是在打印第一个元素后程序意外挂起，

1.I 认为如果 malloc() 失败它会为所有元素正确吗？
2.I 不幸的是必须使用这些结构，下面的代码有什么问题吗？

注：所有字符数组的大小等于它们将接收的内容的最大长度加上一个空终止字符'\0'，每个团队最多有 7 名玩家，团队数量为 21000。
很抱歉出现这种错误检查问题，但我过去从未使用过 C++ 中的结构。

typedef struct Player{
char firstName[50];
char lastName[50];
}Player;

typedef struct Team{
    int id;
    char title[50];
    char summary[100];
    int numberOfPlayers;
    Player *players;
}Team;

typedef struct TeamsLog{
    Team *arr;
    int numberOfTeams;
}Teams;

int main()
{
   TeamsLog log;
   log.numberOfTeams = 21000;
   log.arr = (Team*)malloc(log.numberOfTeams * sizeof(Team));

    for (int i = 0; i < log.numberOfTeams; ++i)
    {
        (log.arr+ i)->id = 1;
        (log.arr + i)->numberOfPlayers = 7;
        for (int l = 0; l < 10; ++l)
        {
            (log.arr + i)->summary[l] = '0' + l;
            (log.arr + i)->title[l] = '0' + l;
        }
        (log.arr + i)->summary[10] = '[=10=]';
        (log.arr + i)->title[10] = '[=10=]';
        log.arr->players = (Player*)malloc(7 * sizeof(Player*));
        for (int l = 0; l < 7; ++l)
        {
            for (int k = 0; k < 10; ++k){
                (log.arr + i)->players[l].firstName[k] = '0' + k;
                (log.arr + i)->players[l].lastName[k] = '0' + k;
            }
            (log.arr + i)->players[l].firstName[10] = '[=10=]';
            (log.arr + i)->players[l].lastName[10] = '[=10=]';
        }
        printstruct(log.arr + i);
     }


}

printstruct()代码：

void printstruct(Team* arg)
{
    cout << "\nTeam Name: " << arg->title
         << "\nId: " << arg->id
         << "\nSummary: " << arg->summary
         << "\nNumber of players: " << arg->numberOfPlayers << endl;
    for (int j = 0; j < arg->numberOfPlayers; ++j)
        cout << "Player " << j+1 << " " << ((arg->players) + j)->firstName << " " 
             << ((arg->players) + j)->lastName << endl;
}

Answer 1

当我 copy/pasted 你的代码时，我遇到了一个段错误，原因如下：

 log.arr->players = (Player*)malloc(7 * sizeof(Player*));

您忘记添加索引，因此它会在您每次执行循环时尝试在同一位置分配内存，从而导致段错误。同样如评论中所述，您应该使用 sizeof(Player) 而不是 sizeof(Player*)。

按照你的风格，应该是：

 (log.arr + i)->players = (Player*)malloc(7 * sizeof(Player));

我建议将 Team *arr 设置为 std::vector，将 Player *players 设置为 std::vector（假设您想要一个动态容器）。 Vector 将负责内存管理（通过其分配器）并将提高代码的可读性并使其在将来更易于使用（代码重用）。

Answer 2

既然你使用的是C++我想给你一些建议，我要写的东西太长了，无法评论，因此被写为答案.

使用智能指针。

使用智能指针，您（通常）不必关心内存管理。

感兴趣的链接：

Smart Pointers (Modern C++), Smart pointer

尽可能使用std::string。

您正在使用 C++ 语言进行编码，怎么不使用它？你一定要使用 char 吗？

同一个程序（C++）：

#include <iostream>
#include <vector>
#include <string>

typedef struct Player{
    std::string firstName;
    std::string lastName;
}Player;

typedef struct Team{
    int id;
    std::string title;
    std::string summary;
    int numberOfPlayers;
    std::vector<Player> players;
}Team;

typedef struct TeamsLog{
    std::vector<Team> arr;
    int numberOfTeams;
}Teams;


void printstruct(const Team& team)
{
    std::cout << "\nTeam Name: " << team.title
        << "\nId: " << team.id
        << "\nSummary: " << team.summary
        << "\nNumber of players: " << team.numberOfPlayers << std::endl;


    int index = 0;
    for (auto &player : team.players)
    {
        std::cout << "Player " << ++index << " " << player.firstName << " " << player.lastName << std::endl;
    }
}

int main()
{
    TeamsLog log;
    log.numberOfTeams = 21000;
    log.arr.reserve(21000);  // This is not really needed but improve performance.

    for (int i = 0; i < log.numberOfTeams; ++i)
    {
        Team team;
        team.id = 1;
        team.numberOfPlayers = 7;

        team.summary = "some summary";
        team.title = "some title";

        team.players.reserve(7);

        for (int l = 0; l < 7; ++l)
        {
            Player player;
            player.firstName = "Some name";
            player.lastName = "Some last name";
            team.players.push_back(player);
        }
        log.arr.push_back(team);
        printstruct(log.arr[i]);
    }
}

打印结构的结构数组会导致意外的执行错误？

Printing an array of structs of structs results in an unexpected execution error?

c++

malloc

struct