c - 为什么我在 malloc 时遇到段错误？

Question

我有以下代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "tournament.h"
Player * draftPlayers(char * filename, int team, int num_players){
Player *player[10];
int it;
for(it=0;it<10;it++)
{
    player[it]=malloc(sizeof(Player));

}
FILE *fp;
char *line = NULL;
size_t len = 0;
ssize_t read;
char *token[100];
int  i=0,j,k;
fp = fopen(filename, "r");
while (getline(&line, &len, fp) != -1) {
    player[it]->first=malloc(sizeof(char)*50);
    player[it]->last=malloc(sizeof(char)*50);
    j=0;
    token[0] = strtok(line, ",");
    while(token[j] != NULL ) {
        j++;
        token[j] = strtok(NULL, ",");
    }

    if(team==atoi(token[0])){
        player[i]->team=atoi(token[0]);
        printf("%s\n","Here3");
        strcpy(player[i]->first,token[1]);
        printf("%s\n","Here3");
        strcpy(player[i]->last,token[2]);
        printf("%s\n","Here3");
        player[i]->number=atoi(token[3]);
        printf("%s\n","Here3");
        player[i]->offensive=atoi(token[4]);
        printf("%s\n","Here3");
        player[i]->defensive=atoi(token[5]);    
        printf("%s\n","Here3");
    }

    i++;    
}

printf("%s\n","Here4");
fclose(fp);
printf("%s\n","Here5");
if (line){
    printf("%s\n","Here6");
    free(line);}
printf("%s\n","Here7");
return player;

}

我得到输出:

Here3
Here3
Here3
Here3
Here3
Here3
Here4
Here5
Here6
Here7
Here3
Here3
Here3
Here3
Here3
Here3
Segmentation fault

请让我知道我的错误。我已经尝试了一切，但无法找到错误的根源。我想知道我在这里做错了什么。我无法理解为什么会出现段错误。

我将 main 称为:基本上我调用的是与上面相同的函数。

#include"tournament.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(){
  Player * draft = draftPlayers("players.dat", 1, 10);
}

我实现的结构是:

锦标赛.h:

typedef struct {
  int offensive;
  int defensive;
  int number;
  int team;
  char * first;
  char * last;
}Player;

玩家.dat:

0,Mei,Fellgatt,24,8,2
1,Richmound,Beazley,45,6,7
2,Gunther,Fackney,73,6,7
3,Stewart,Frowing,19,3,3
4,Sallee,Cuffley,70,2,4
5,Axel,Stollwerk,73,7,2
6,Othilie,Grigoliis,28,8,1
7,Igor,Claffey,28,8,3
8,Bruce,Schruur,73,5,2
9,Clovis,Wynes,59,8,4
10,Silvie,Thiolier,5,4,5
11,Maxie,Treher,57,6,6
12,Margette,Wraighte,44,8,2
13,Chryste,Byrnes,41,10,3
14,Ulysses,Sturmey,68,9,7
15,Woodman,Powrie,81,4,4
16,Zitella,Reddel,14,6,4
17,Bronny,McMearty,42,2,5
18,Jewel,Cheyney,14,2,4
19,Adelaida,Gunney,44,6,2
20,Adrienne,O'Looney,21,5,6
21,Branden,Wilcott,27,7,5
22,Etta,Nuth,41,8,2
23,Karney,Lightbowne,80,3,6
24,Pierson,Crippell,6,1,4
25,Lutero,Filchagin,26,3,7
26,Roth,Ferrierio,66,5,1
27,Gothart,Thickens,16,1,4
28,Dwain,Josuweit,4,5,2
29,Nanice,Eady,47,2,6
30,Zahara,Ousley,79,10,4
31,Nichols,Earle,7,8,6
0,Jodee,Sharple,42,2,3
1,Cordy,Tuckwood,29,6,1
2,Jillian,Neligan,22,9,3
3,Shirlene,Wrought,23,4,4
4,Shoshana,Wais,14,7,2
5,Julissa,Edinburough,26,8,3
6,Gerome,Hallbord,2,7,5
7,Vere,Riste,7,1,3
8,Dexter,Gecke,3,3,5
9,Jacintha,Cessford,96,3,1
10,Kerry,Cramphorn,1,2,6
11,L;urette,McCluskey,37,6,2
12,Birch,Jagoe,37,6,2
13,Lenore,Norvel,55,1,4
14,Eilis,Klink,88,3,4
15,Neil,Darrel,37,1,5
16,Imelda,Donner,26,7,4
17,Alexandro,Kilbee,10,7,6
18,Gram,Tregunna,28,10,7
19,Jdavie,Bampford,26,4,4
20,Robyn,Spinola,43,9,5
21,Yance,Cochern,16,7,6
22,Rogers,Blyden,15,5,3
23,Jerrilee,Tremlett,1,2,3
24,Nickie,Winsome,14,4,7
25,Andrew,Duetsche,63,4,2
26,Dewey,Mitten,6,2,1
27,Aldon,Dunkirk,43,4,3
28,Curtice,Egginson,54,3,1
29,Carly,Loisi,98,7,4
30,Chrissie,Keppe,1,5,6
31,Jenny,Harbidge,81,2,5

Answer 1

正如您在评论中指出的那样，您的代码中有一些错误:

• 您返回本地数组的地址。这是一个指针数组。您分配给这些指针，但是一旦您离开该函数，数组本身就会超出范围(并且分配的内存将被泄漏)。另外player是 Player **衰减为指针后，ot a Player * ，这是函数的返回类型。
• 您混淆了循环中的各种索引。
• 您的分配还为时过早。例如，当您还不知道有多少个玩家时，您不需要为所有十个玩家分配内存。分配 50 个字符，因为“这可能就足够了”是另一种情况:复制字符串时根据字符串长度分配。 (非标准函数 strdup 可以为您完成此操作。)

您的函数应该将某个团队的所有球员从文件读取到球员列表中。调用函数需要查看数组以及该数组中有多少个元素。

一种方法是返回分配的玩家数组并通过指针更改玩家数量。调用者必须在使用后释放内存(以及名字和姓氏的内存)。此函数应在附加另一个玩家之前重新分配数组。)

这是执行此操作的程序:

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

typedef struct Player Player;

struct Player {
    int team;
    char *first;
    char *last;
    int number;
    int offensive;
    int defensive;
};

Player *draftPlayers(char *filename, int team, int *nplayer)
{
    Player *player = NULL;

    FILE *fp;
    char *line = NULL;
    size_t len = 0;

    fp = fopen(filename, "r");

    *nplayer = 0;

    while (getline(&line, &len, fp) != -1) {
        char *tk;
        char *token[6];
        int j = 0;

        tk = strtok(line, ",");
        while (tk && j < 6) {
            token[j++] = tk;
            tk = strtok(NULL, ",");
        }

        if (j == 6 && team == atoi(token[0])) {
            player = realloc(player, (*nplayer + 1) * sizeof(*player));

            player[*nplayer].team = atoi(token[0]);
            player[*nplayer].first = strdup(token[1]);
            player[*nplayer].last = strdup(token[2]);
            player[*nplayer].number = atoi(token[3]);
            player[*nplayer].offensive = atoi(token[4]);
            player[*nplayer].defensive = atoi(token[5]);
            (*nplayer)++;
        }
    }

    fclose(fp);
    free(line);

    return player;
}

int main()
{
    int t;

    for (t = 1; t < 36; t++) {
        int n;
        Player *player = draftPlayers("kk", t, &n);

        if (n) {
            int i;

            printf("Team %d\n", t);

            for (i = 0; i < n; i++) {
                Player *p = player + i;

                printf("%d: %s %s (%d, %d, %d)\n",
                    i + 1, p->first, p->last,
                    p->number, p->offensive,p->defensive);

                free(p->first);
                free(p->last);
            }

            free(player);
            puts("");
        }        
    }

    return 0;
}

(这并不理想，但我试图尽可能接近您的原始函数。在实际代码中，当然，对 fopen 和 realloc 的所有调用都应该进行适当的错误检查。 )