blocks|key|2735674|text|如果您在托管环境(在带有操作系统的系统上运行)中工作，则main()应具有标准格式(int+main(void))并返回示例1中的int+value|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2735675|。你没有给你的指针分配任何内存，在你的第二个例子中有一个内存泄漏，在你的第二个例子中，你没有释放obj|unordered-list-item|2735676|
|2735677|You中的内存，在你的第二个例子中，没有给struct+Foo|2735678|2735679|Core+dump中的pName分配任何内存，这意味着出了很大的问题。|2735680|2735681|entityMap|0|LINK|mutability|MUTABLE|url|http://whatis.techtarget.com/definition/core-dump^0|S|6|16|E|1T|3|0|1C|3|0|0|L|A|0|0|B|5|0|9|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|I|3|J|5|6|7|18|8|@]|D|@]|E|$]]|$1|K|3|L|5|H|7|19|8|@$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|M|3|J|5|6|7|1C|8|@]|D|@]|E|$]]|$1|N|3|O|5|H|7|1D|8|@$9|1E|A|1F|B|C]]|D|@$9|1G|A|1H|1|1I]]|E|$]]|$1|P|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

<ol>
<li>You do not assign values inside a struct definition</li>
<li>Assuming you are working in a hosted environment (running on a system with an OS), <code>main()</code> should have the standard form (<code>int main(void)</code>) and return an <code>int</code> value</li>
<li>In example one, you didn't assign any memory to your pointer <code>s</code></li>
<li>You have a memory leak in your second example where you didn't free the memory in <code>obj</code></li>
<li>You didn't assign any memory in your second example to <code>pName</code> within <code>struct Foo</code></li>
<li><a href="http://whatis.techtarget.com/definition/core-dump" rel="nofollow">Core dump</a> means something went very wrong.</li>
</ol>

blocks|key|610650|text|为该结构声明了一个指针，但该指针从未初始化，也从未创建过任何结构。s指向一些随机内存空间，您可以尝试从中读取数据。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|610651|在第二种情况下，您有一个从未分配过内存的指针pName。它还指向一个随机的内存空间。您正在从字符串文字复制字符串，并写入一个随机的内存位置。|610652|entityMap^0|X|1|0|M|5|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

A pointer is declared for the structure, but the pointer is never initialized, no structure is never created. <code>s</code> is pointing to some random memory space, from whic you attempt to read.

In the second case, you have a pointer <code>pName</code> which has never been allocated memory. It is also pointing to a random memory space. You are string copying from the string literal and writing a random memory location.

blocks|key|2735759|text|在示例1中，您声明了一个指针，但尚未对其进行初始化。因此，指针指向未知位置。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2735760|在示例2obj->pname中，出于同样的原因，指向内存的未知部分(它未初始化)，因此尝试在strcpy中访问它将使程序崩溃。|2735761|你应该做的:你应该为指针分配一些内存，让它们指向属于你的内存，而不是一些随机的内存(非法？)内存的一部分|2735762|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

In example 1 you declared a pointer but you have not initialized it. Therefore the pointer points to an unknown location.

In example 2 obj->pname for the same reason points to An Unknown portion of the memory (it was not initialized) and therefore trying to acess it inside strcpy will crash the program.

What you should have done: you should have allocated some memory for the pointers to make them point to memory that belongs to you and not some random (illegal?) portion of memory

blocks|key|1128444|text|+++#include+<stdio.h>+
+++#include+<stdlib.h>+
+++int+main()
+++{
+++++struct+xx
+++++{
+++++++int+x;
+++++++char+name[25];++/*+mention+size+of+array+*/
+++++};

+++++struct+xx+*s;
+++++s=(struct+xx+*)malloc(sizeof(struct+xx));+++/*+allocate+the+size+for+pointer+variable+*/
+++++printf("Enter+the+value\n");
+++++scanf("%25d",&s->x);+++++++++++/*get+the+value+*/
+++++printf("Enter+the+name\n");
+++++scanf("%25s",s->name);+++++++++
+++++printf("%25d\n",s->x);++++++++++/*get+the+value+*/
+++++printf("%25s\n",s->name);
+++++return+0;
+++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1128445|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code> #include &lt;stdio.h&gt; 
 #include &lt;stdlib.h&gt; 
 int main()
 {
 struct xx
 {
 int x;
 char name[25]; /* mention size of array */
 };

 struct xx *s;
 s=(struct xx *)malloc(sizeof(struct xx)); /* allocate the size for pointer variable */
 printf("Enter the value\n");
 scanf("%d",&amp;s-&gt;x); /*get the value */
 printf("Enter the name\n");
 scanf("%s",s-&gt;name); 
 printf("%d\n",s-&gt;x); /*get the value */
 printf("%s\n",s-&gt;name);
 return 0;
 }
</code></pre>

blocks|key|6088229|text|您已声明了指针变量，但尚未为其分配内存以在strict+xx+*S;之后进行添加|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|6088230|S=(struct+xx*)+malloc(sizeof(strict+xx));|code-block|syntax|javascript|6088231|并声明char+name[30]的第一大小；|6088232|entityMap^0|L|D|0|0|3|D|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

You have declared the pointer variable but have not allocated memory to it
To do add after <code>strict xx *S;</code>

<pre><code>S=(struct xx*) malloc(sizeof(strict xx));
</code></pre>

And also declare first size of <code>char name[30]</code>;

blocks|key|2735844|text|首先，你需要分配变量s的大小，因为你的编译器不知道它应该分配给变量的内存大小。这就是为什么你需要这样分配内存:+S=(struct+*)malloc+(sizeof(struct+))；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2735845|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

First you need to allocate size of your variable s because your compiler donot understand the size of memory it should allocate to variable. Thats why you need to allocate memory as:
S=(struct xx*)malloc (sizeof(struct xx));

blocks|key|1132223|text|结构中的指针在使用时不会被初始化(这称为野指针)。即使指针已经初始化，它也应该指向有效的内存区。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1132224|在学习C语言时，内存操作是最重要的。|1132225|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The pointer in the struct is not initiallized when being used(which is called wild pointer). Even though the pointer has been initialized, it shoud point to an effective memory area.

When learning C language, memory operation is the top thing.

I'm learning the C language. Can anybody help me to understand the following result:

<pre><code>int main()
{
 struct xx
 {
 int x;
 char name[];
 };
 struct xx *s;
 printf("%d",s-&gt;x);
 printf("%s",s-&gt;name);
 return 0;
}
</code></pre>

output:- Segmentation fault

I wrote another code which is:

<pre><code>struct Foo
{
 char *pName;
};

int main()
{
 struct Foo *obj = malloc(sizeof(struct Foo));
 strcpy(obj-&gt;pName,"Your Name");
 printf("%s", obj-&gt;pName);
 return 0;
} 
</code></pre>

output : Segmentation Fault (core dumped);

Why am I getting segmentation fault? What's wrong with the code? What is the meaning of core dumped ?

C language structure

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在学习C语言。有谁能帮我理解一下下面的结果：int main(){  struct xx  {    int x;    char name[];  };  struct xx *s;  printf("%d",s->x);  printf("%s",s->name);   return 0;}输出：-分段故障我写了另一个代码，它是：struct Foo{  char *pName;};int

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