C struct字段赋值会覆盖另一个字段

Question

我正在写一个有趣的幻想足球选秀计划.

我遇到了一个奇怪的问题.我为一个struct字段分配了一个值,但这也发生了,但它也将该值赋给了另一个字段struct.为凌乱的调试printf语句道歉.

我显然不了解struct字段分配.

码:

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

#define TRUE 1

int QB_count = 0;
int RB_count = 0;
int WR_count = 0;
int TE_count = 0; 
int DEF_count = 0;

struct Player { 
    char *name;
    char *position;
    int age;
    int bye_week;
};

int get_name (struct Player *drafted) {
    char name[20];
    fputs("Enter Player Name: ", stdout);
    fflush(stdout);
    if (fgets(name, sizeof name, stdin) != NULL){
        char *newline = strchr(name, '\n');
        if (newline != NULL){
            *newline = '\0';
        }
        drafted->name = name;
        printf("You've drafted: %s\n", drafted->name);
    }
    return 0;
}

int get_position(struct Player *drafted){
    char position[20];
    int depth;
    char *nametemp = drafted->name;
    printf("nametemp: %s\n", nametemp);
    fputs("Enter Player Position in 'QB/RB/WR/TE/DEF' format: ", stdout);
        fflush(stdout);
        if (fgets(position, sizeof position, stdin) != NULL){
                char *newline = strchr(position, '\n');
                if (newline != NULL){
                        *newline = '\0';
                }
                drafted->position = position;

        if (strcmp(position, "QB") == 0){
            QB_count++;
            depth = QB_count;

        } else if (strcmp(position, "RB") == 0){
                        RB_count++;
                        depth = RB_count;

                } else if (strcmp(position, "WR") == 0){
                WR_count++;
                        depth = WR_count;

                } else if (strcmp(position, "TE") == 0){
                        TE_count++;
                        depth = TE_count;

                } else if (strcmp(position, "DEF") == 0){
                        DEF_count++;
                        depth = DEF_count;

                } else {
            printf("Please re-enter position information using the format 'QB' or 'qb'\n");
            get_position(drafted);
            return 0;
        }
        drafted->name = nametemp;
        printf("NAME: %s\n", drafted->name);
        printf("You've drafted %s at: %s%d\n", drafted->name, drafted->position, depth);
        }
        return 0;

}

int get_age (struct Player *drafted){
    return 0;
}

int get_bye_week (struct Player *drafted){
    return 0;
}

int main (){ 
    int stop = 0;
    char text[20];
    while (TRUE){
        struct Player drafted;
        printf("Welcome to the 2012 Draft Day Program\n");
        get_name (&drafted);
        printf("NAME_MAIN: %s\n", drafted.name);
        get_position(&drafted);
        printf("You've drafted %s at: %s\n", drafted.name, drafted.position);
        get_age(&drafted);
        get_bye_week(&drafted);
        fputs("Would you like to draft another player?\n" 
            "Enter '1' for no, '0' for yes\n", stdout);
        fflush(stdout);
        if(fgets(text, sizeof text, stdin)){
            int number;
            if (sscanf(text, "%d", &number) == 1){
                if (number == 1){
                    printf("Draft Ended!\n");
                    break;
                }       
            }
        }
    }
    return 0;
}

结果输出是:

Welcome to the 2012 Draft Day Program
Enter Player Name: Aaron Rodgers
You've drafted: Aaron Rodgers
NAME_MAIN: Aaron Rodgers
nametemp: Aaron Rodgers
Enter Player Position in 'QB/RB/WR/TE/DEF' format: QB
NAME: QB
You've drafted QB at: QB1
You've drafted QB at: QB
Would you like to draft another player?
Enter '1' for no, '0' for yes
1
Draft Ended!

为什么drafted.name成为"QB"？

Answer 1

在您的get_name函数中,您将分配给堆栈变量的name字段.struct Playername

在这一行:

drafted->name = name;

name在函数中声明,因此它的范围仅限于该函数.一旦get_name返回,变量就会超出范围,并尝试使用该内存调用未定义的行为.

您需要为drafted->name使用分配空间,而不是使用简单赋值,malloc并使用它strncpy来制作名称的副本.如果strdup可用,您可以使用它来分配空间并在一个步骤中执行复制.或者,您可以drafted->name在读取名称之前为其分配空间,并使用它代替name变量.

作为最后一个选项,如果假设名称的最大长度 - 当前代码允许的名称最多为字符串长度19- 您可以简单地为每个struct Player名称声明一个大小的数组:

struct Player
{ 
    char name[NAME_MAXLEN];

您position在get_position函数中的字段存在相同的问题.