赋值时将整数指针，未在C语言中施放[默认启用]

Question

代码：

#include<stdio.h> 
#include<stdlib.h> 
struct node 
{ 
    int data; 
    struct node *next; 
}; 
struct node *head,*temp; 
int insert_end(int); 
int insert_begin(int); 
int display(void); 
int delete_end(void); 
int delete_begin(void); 

int main() 
{ 
    head=(struct node *)malloc(sizeof(struct node)); 
    temp=(struct node *)malloc(sizeof(struct node)); 
    head->next = -1; 
    int choice,a,b; 
label: 
printf("\n\t1.insert_end 2. insert_begin 3.\n delete_end 4.delete_begin \n5.display 6.exit "); 
scanf("%d",&choice); 
switch (choice) 
{ 
    case 1: 
{ 
    printf("\tenter the no to be insert at the end "); 
    scanf("%d",&a); 
    insert_end (a); 

    goto label; 

} 
case 2: 
printf("\tenter the no to be insert at the beginnig "); 
scanf("%d",&a); 
insert_begin (a); 

goto label; 

case 3: 
{ 
    b = delete_end(); 
    if (b == 0) 
    {  
     printf(" \t\tfailed ! ! \n");} 
     else 
     { 
      printf(" \t\t success ! ! \n");} 

     goto label; 
} 

case 4: 
{ 
    b = delete_begin(); 
    if (b == 0) 
    { 
     printf(" \t\tfailed ! ! \n");} 
    else 
    { 
     printf(" \t\t success ! ! \n");} 

     goto label; 
    } 
case 5: 
{ 
    temp =head ; 
    display(); 
    goto label; 
} 
case 6: 
{ 
    exit (0); 
} 
default: 
{ 
    printf("wrong options"); 
    goto label; 
} 

} 
} 

int insert_end (int a) 
{ 
temp = head; 
while (1) 
{ 
    if (temp->next == -1) 
    { 
     temp->data =a; 
     temp->next =0; 
     return 0; 
    } 
     else if (temp->next == 0) 
     { 
      temp->next = malloc(sizeof (struct node)); 
      temp =temp->next; 
      temp->data =a; 
      temp->next =0; 
      return 0; 
     } 
     else 
     { 
      temp = temp->next; 
     } 
    } 
} 


int display() 
{ 
temp=head; 
while (1) 
{ 
    if (head->next == -1) 
    { 
     printf("\tEmpty ! ! !\t\n"); 
     break; 
    } 
    else if ((head->next == 0)) 
    { 
     printf(" %d ", head->data); 
     break; 
    } 
else if (temp->next != 0) 
{ 
    printf (" %d ->", temp->data); 
    temp =temp->next ; 
} 
else if (temp->next == 0) 
{ 
    printf(" %d ", temp->data); 
    return 0; 
} 
} 
} 


int insert_begin(int a) 
{ 
if(head->next == -1) 
{ 
    head->data =a; 
    head->next=0; 
    return 1; 
} 
else 
{ 
    temp =malloc(sizeof (struct node)); 
    temp->data =a; 
    temp->next = head; 
    head = temp; 
    return 1; 
} 
} 

int delete_end (void) 
{ 
temp=head; 
while (1) 
{ 
    if (head->next == -1) 
    { 
     return 0; 
    } 
    else if (head->next == 0) 
    { 
     head->next = -1; 
     return 1; 
    } 
    else if (temp->next->next == 0) 
    { 
     temp->next =0; 
     return 1; 
    } 
    else 
    temp=temp->next; 
} 
} 


int delete_begin(void) 
{ 
if (head->next == -1) 
{ 
    return 0; 
} 
    else if (head -> next == 0) 
    { 
      head->next = -1; 
      return 1; 
    } 
    else 
    { 
     head=head->next; 
     return 1; 
    } 
} 

error: 

linkedlist1.c: In function ‘main’: 

linkedlist1.c:19:12: warning: assignment makes pointer from integer without a cast [enabled by default] 

head->next = -1; 
     ^
linkedlist1.c: In function ‘insert_end’: 

linkedlist1.c:87:16: warning: comparison between pointer and integer [enabled by default] 
if (temp->next == -1) 
      ^
linkedlist1.c: In function ‘display’: 

linkedlist1.c:115:16: warning: comparison between pointer and integer [enabled by default] 
if (head->next == -1) 
      ^
linkedlist1.c: In function ‘insert_begin’: 

linkedlist1.c:141:15: warning: comparison between pointer and integer [enabled by default] 
if(head->next == -1) 
     ^
linkedlist1.c: In function ‘delete_end’: 

linkedlist1.c:162:16: warning: comparison between pointer and integer [enabled by default] 
if (head->next == -1) 
      ^
linkedlist1.c:168:12: warning: assignment makes pointer from integer without a cast [enabled by default] 
head->next = -1; 
     ^
linkedlist1.c: In function ‘delete_begin’: 

linkedlist1.c:184:17: warning: comparison between pointer and integer [enabled by default] 
if (head->next == -1) 
      ^
linkedlist1.c:190:12: warning: assignment makes pointer from integer without a cast [enabled by default] 
head->next = -1; 
     ^

当我试着使用GCC编译，我结束了，上面写着警告“分配，使指针从整如果没有投射[默认启用]，请帮我解决上述警告，我不知道错误是什么，

Answer 1

用你的“警告”，你还会得到一个字符串数字，其中出现“warning” 请给出出现错误的字符串

我没有在第一次看到你的警告

只需更换-1 NULL或更换-1 (void *)-1

课程标准应写入NULL，但如果你真的愿意，你可以写(void *)-1

Answer 2

编译器不被满足声明

head->next = -1; 

这将是更好，如果你会使用NULL，而不是-1和写入

head->next = NULL;