#include<stdio.h>
#include<stdlib.h>
#define GREY 1
#define BLACK 0
#define WHITE 2
typedef struct node * graph;
typedef struct stack * snode;
graph cnode(int data); //cnode is to create a node for graph
void cgraph(void);
struct node {
int data, color;
struct node *LEFT, *RIGHT, *TOP, *DOWN;
};//this structure defines a node of the graph
struct stack {
struct stack *priv;
struct cgraph *graph_node;
};// this is to define a structure which should hold node of a structure
extern snode sroot;
我定义了一个头文件(declaration.h),如上所示,以下是我正在开发的库中使用的ac程序(stack.c)
#include<declarations.h>
void cstack (graph temp);
void stackpush(snode stemp);
extern int stack_counter = 0;
sroot=NULL;
void cstack (graph gtemp) //cstack is to create stack
{
snode spriv,some;
if (stack_counter==0)
{
sroot=stackpush(gtemp);
spriv=sroot;
stack_counter++;
}
else{
some=cstacknode(gtemp);
some->priv=spriv;
spriv=some;
}
}
//struct stack is representing a stack
//struct node is representing a node in graph
snode cstacknode (graph gtemp)
//this function should create a node of the stack which should be storing the graph node as a pointer
{
snode an;
an=(snode)malloc(sizeof(snode));
an->graph_node=gtemp;
an->priv=NULL;
return an;
}
void stackpush(snode stemp)
{
}
以上两个文件都在同一目录中.我编译了上面的文件stack.c
cc -I ./ stack.c我发出警告
stack.c:4: warning: ‘stack_counter’ initialized and declared ‘extern’
stack.c:6: warning: data definition has no type or storage class
stack.c:6: error: conflicting types for ‘sroot’
./declarations.h:21: note: previous declaration of ‘sroot’ was here
stack.c:6: warning: initialization makes integer from pointer without a cast
stack.c: In function ‘cstack’:
stack.c:12: warning: passing argument 1 of ‘stackpush’ from incompatible pointer type
stack.c:3: note: expected ‘snode’ but argument is of type ‘graph’
stack.c:12: error: void value not ignored as it ought to be
stack.c:13: warning: assignment makes pointer from integer without a cast
stack.c:17: warning: assignment makes pointer from integer without a cast
stack.c: At top level:
stack.c:27: error: conflicting types for ‘cstacknode’
stack.c:17: note: previous implicit declaration of ‘cstacknode’ was here
stack.c: In function ‘cstacknode’:
stack.c:32: warning: assignment from incompatible pointer type
我想知道当我将变量声明为extern并且我已经标记为粗体时为什么我会将其作为警告对此有任何想法,如果有人想要在剩余错误上分享任何其他事情,请告诉我.
AnT*_*AnT 37
虽然您的代码包含许多相当严重且明显的错误(已在其他答案中涵盖),但您在问题标题中添加的警告是完全无意义的无意义警告.GCC编译器因发布无用警告而臭名昭着.这些警告中的许多似乎都源于某人的无能和完全没有根据的信念,即做某事"某种程度上是错误的",而实际上并没有任何问题.
在您的情况下,警告由触发
extern int stack_counter = 0;
宣言.显然,警告的"作者"认为extern说明者应该保留用于非定义的声明.在这种情况下,初始化程序的存在= 0将声明转换为定义(因此正式使其成为extern可选).尽管如此,它并没有错误,事实上,extern这里可能非常欢迎强调这一事实stack_counter是一个全局变量.
同样,您是否需要全局变量是一个不同的问题,同样,您的代码包含大量其他错误.但是你似乎关注的警告并不值得.只需在编译器设置中禁用此警告(并且,请向GCC团队写一封关于它的粗略信函).
头文件中的extern声明允许除定义变量之外的模块使用它.如果它应该被定义为int stack_counter = 0并存在于stack.c中,那么将其定义为并extern stack_counter在头文件中放置一个.
在stack.c的第6行,您没有为sroot定义存储类.由于它在标题中被删除,我认为你打算输入snode sroot=NULL.
修复这些,然后实现stackpush(确保它不返回void)并按顺序处理其余的警告.请注意,在C中,您必须使用函数的前向声明(使用原型)或在使用之前定义函数.该cstack函数可能应该是文件中的最后一个函数.
我刚刚收到 gcc 的警告，这是一个简单的修复。stack_counter 不应在标头中初始化，而应在包含它的源文件中初始化。所以标题应该只使用：
extern int stack_counter;
然后在包含该标头的一个源文件的全局范围内声明并初始化 stack_counter：
int stack_counter = 0;