C语言链表代码出现不兼容指针类型警告的原因及修复方法

你碰到的这个警告，根源在于结构体定义时的类型声明混乱：

你的代码里用typedef struct { ... } player;定义了一个匿名结构体的别名player，但结构体内部的next指针写的是struct player *next——这里的struct player是一个完全没被定义过的全新结构体类型，和你typedef出来的player根本不是一回事。这就导致当你把player*类型的变量（比如newPlayer）赋值给struct player*类型的next，或者反过来赋值时，编译器会判定这是两种不兼容的指针类型，于是抛出警告。

有两种简单靠谱的修复方式，选哪种都可以：

方式一：给结构体加上标签，让内部指针和typedef类型匹配 #

修改结构体的typedef定义，给结构体加上player标签，这样内部的struct player *next就会指向这个带标签的结构体，和typedef后的player类型完全统一：

typedef struct player {
    int number;
    struct player *next;
} player;

方式二：先声明typedef别名，再用别名定义内部指针 #

这种写法需要先提前声明typedef的名称（C语言允许这种前置声明），然后在结构体里直接用别名声明指针：

typedef struct player player; // 先typedef前置声明

struct player {
    int number;
    player *next; // 直接用已声明的player别名
};

这里给出用方式一修复后的完整代码，编译时已经不会再出现类型不兼容的警告：

#include<stdio.h>
#include<stdlib.h>
typedef struct player {
    int number;
    struct player *next;
}player;
player *newPlayer;
player *firstPlayer;
player *currentPlayer;
int main(void) {
    newPlayer = malloc(sizeof(player));
    firstPlayer = newPlayer;
    currentPlayer = newPlayer;
    currentPlayer->next = NULL;
    printf("Please enter Head: ");
    scanf("%d", &currentPlayer->number);
    newPlayer = malloc(sizeof(player));
    currentPlayer->next = newPlayer;
    currentPlayer = newPlayer;
    currentPlayer->next = NULL;
    printf("Please enter second element: ");
    scanf("%d", &currentPlayer->number);
    currentPlayer = firstPlayer;
    while (currentPlayer) {
        printf("%d ", currentPlayer->number);
        currentPlayer = currentPlayer->next;
    }
    printf("\n");
}

内容的提问来源于stack exchange，提问作者J0S