关于指针的快速问题 [英] quick question about pointers
问题描述
大家好，
我有一个关于指针的快速问题。
当我说
int * p;
* p = 40;
cout<< * p;
为什么会产生错误信息（有关故障地址的信息）？
不是我创建了一个指针，我指出它的值为40和
然后显示它？！
Thanx很多，非常感谢任何帮助
玩得开心
Hello guys,
I have a quick question about pointers.
When I say
int *p;
*p = 40;
cout << *p;
why does that produce and error message(something about fault address)?
Isnt that I created a pointer and I made it point to the value of 40 and
then display it?!
Thanx alot,any help is really appreciated
Have fun
推荐答案
Snake写道：
Snake wrote:
大家好，
我有一个关于指针的快速问题。
当我说
int * p;
p现在指向什么？
* p = 40;
这就是说将40复制到位置p指向。
cout<< * p;
为什么会产生错误信息（有关故障地址的信息）？
我不是创建了一个指针而是指向40的值然后显示它？ ！
Hello guys,
I have a quick question about pointers.
When I say
int *p;
What does p now point to?
*p = 40;
That says "copy 40 into the location p points to".
cout << *p;
why does that produce and error message(something about fault address)?
Isnt that I created a pointer and I made it point to the value of 40 and
then display it?!
C ++的一个乐趣就是如果你不指定变量，它包含
垃圾。未来的行为是未定义的。
在这种情况下，p指向任何地方。分配可能会崩溃，或者可能会起作用 -
'未定义。
-
Phlip
< a rel =nofollowhref =http://www.xpsd.org/cgi-bin/wiki?TestFirstUserInterfacestarget =_ blank> http://www.xpsd.org/cgi-bin/wiki?Tes ... UserInterfaces
指针：
- 指向某事
- 无所事事
默认情况下，指针指向任何东西。
所以，在你的情况下，你创建一个指针没有任何意义，然后尝试
取消引用任何内容并分配值。
编译器不会将此标记为错误，实际发生的是
undefined（在受保护模式的环境中，大多数时候这会导致崩溃
类似于你所描述的）。
因此，根据您想要做的具体操作，首先必须使您的
指针指向取消引用和赋值之前的某些内容。 （
* p是取消引用，= 40分配值。）
所以，你可以将p指向已经存在的东西，例如as：
int i;
int * p =& i;
//等。
或让你的指针指向一些已分配的内存，例如：
int * p = new int;
//等。 （不要忘记通过删除释放分配的内存p
Dig？
Snake写道：
Pointers either:
- point to something
- point to nothing
By default, pointers point to nothing.
So, in your case, you create a pointer that points to nothing, then try to
dereference nothing and assign value.
The compiler will not flag this as an error, and what actually happens is
undefined (in a protected-mode environment, most times this will cause a crash
similar to what you describe).
So, depending on what specifically you want to do, you first must make your
pointer point to something prior to dereferencing and assiging a value. (The
*p is the dereference, the = 40 is assigning the value.)
So, you could point p to something that already exists, such as:
int i;
int *p = &i;
//etc.
or have your pointer point to some allocated memory, such as:
int *p = new int;
//etc. (don''t forget to release the allocated memory through delete p
Dig?
Snake wrote:
大家好，
我有一个关于指针的快速问题。
当我说
int * p;
* p = 40;
cout< ;< * p;
为什么会产生错误信息（有关故障地址的信息）？
我不是创建了一个指针，而是指向40的值，然后
然后显示它？！
Thanx很多，非常感谢任何帮助
玩得开心
Hello guys,
I have a quick question about pointers.
When I say
int *p;
*p = 40;
cout << *p;
why does that produce and error message(something about fault address)?
Isnt that I created a pointer and I made it point to the value of 40 and
then display it?!
Thanx alot,any help is really appreciated
Have fun
-
Bret Pehrson
mailto：br ** @ infowest.com
NOSPAM - 在所有电子邮件中包含此密钥<< 38952rglkwdsl>>
--
Bret Pehrson
mailto:br**@infowest.com
NOSPAM - Include this key in all e-mail correspondence <<38952rglkwdsl>>
" Snake" ha *** @ rogers.com>在留言中写道
news：50 **** **************@twister01.bloor.is.net.c able.rogers.com ...
"Snake" <ha***@rogers.com> wrote in message
news:50******************@twister01.bloor.is.net.c able.rogers.com...
你好，
我有一个关于指针的快速问题。
当我说
int * p;
* p = 40;
cout<< * p;
为什么会产生错误信息（有关故障地址的信息）？
我不是创建了一个指针而是指向40的值然后显示它？ ！
Hello guys,
I have a quick question about pointers.
When I say
int *p;
*p = 40;
cout << *p;
why does that produce and error message(something about fault address)?
Isnt that I created a pointer and I made it point to the value of 40 and
then display it?!
编号你创建了一个指针并指向无处（某些垃圾地址）。
然后你尝试在该位置写东西。崩溃是不可避免的。
指针在尝试与它们进行任何
操作之前应始终包含一些有效地址。
int i;
int * p;
p =& i; // OK
// p现在指向一个有效的内存地址。
或者
int * p = new INT（42）; //好吧
// p现在指向一个虚拟动态商店地址。
删除p;
祝福，
Sharad
No. You created a pointer and made it point to nowhere (some garbage address).
Then you try to write something into that location. A crash is inevitable.
Pointers should always contain some valid address before you try to do any
operations with them.
int i;
int *p;
p= &i; //OK
// p is now pointing to some valid memory address.
or else
int *p = new int(42); //OK
// p now points to a vaild dynamic store address.
delete p;
Best wishes,
Sharad
这篇关于关于指针的快速问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
