char *可以指向任何字节吗？！ [英] char * can point to any byte?!

问题描述

在以下网站上常见问题

http： //c-faq.com/strangeprob/ptralign.html


"通过将char *（可以指向任何字节）转换为int *或

long int *，然后指向它，你最终可能会要求

处理器从未对齐的地址获取多字节值，这是
它不愿意这样做。


char *如何指向任何字节，但int *不能？有人可以澄清这个吗？


谢谢

乍得

解决方案

Chadaécrit：

char *如何指向任何字节，但int *不能？有人可以澄清这个吗？

char *是一个指向char的指针，它是一个字节的大小。

一个int可以由多个字节定义。

loufoque写道：

Chadaécrit：

char *如何指向任何字节，但int *不能？有人可以澄清这个吗？

char *是一个指向char的指针，它是一个字节的大小。
一个int可以由多个字节定义。

换句话说，char *可以指向int中的第2或第3个字节？

"乍得" < CD ***** @ gmail.com>写道：

在以下网站上常见问题

http://c-faq.com/strangeprob/ptralign.html

"通过将char *（可以指向任何字节）转换为int *或
long int *，然后指向它，你最终可能要求
处理器从未对齐的地址获取多字节值，这是不愿意做的。

char *如何指向任何字节，但int *不能？有人可以澄清这个吗？

例如，在某些系统上，int是4个字节长，并且只能是

存储在4的倍数的地址。在这种情况下，int *

不能合法地指向奇数地址。


细节将因系统而异。在某些系统上，

int *具有与char *不同的表示形式，并且int *不是
甚至物理上能够指向单个字节。


-

Keith Thompson（The_Other_Keith） ks *** @ mib .org < http://www.ghoti.net/~kst>

圣地亚哥超级计算机中心< *> < http://users.sdsc.edu/~kst>

我们必须做点什么。这是事情。因此，我们必须这样做。

On the following sites faq

http://c-faq.com/strangeprob/ptralign.html

"By converting a char * (which can point to any byte) to an int * or
long int *, and then indirecting on it, you can end up asking the
processor to fetch a multibyte value from an unaligned address, which
it isn''t willing to do. "

How can char * point to any byte, but int * can''t? Can someone clarify
this?

Thanks
Chad

解决方案

Chad a écrit :

How can char * point to any byte, but int * can''t? Can someone clarify
this?

char* is a pointer to a char, which is the size of a byte.
an int may be defined by multiple bytes.

loufoque wrote:

Chad a écrit :

How can char * point to any byte, but int * can''t? Can someone clarify
this?

char* is a pointer to a char, which is the size of a byte.
an int may be defined by multiple bytes.

So in other words, char * could point to the 2nd or 3rd byte in int?

"Chad" <cd*****@gmail.com> writes:

On the following sites faq

http://c-faq.com/strangeprob/ptralign.html

"By converting a char * (which can point to any byte) to an int * or
long int *, and then indirecting on it, you can end up asking the
processor to fetch a multibyte value from an unaligned address, which
it isn''t willing to do. "

How can char * point to any byte, but int * can''t? Can someone clarify
this?

For example, on some systems an int is 4 bytes long, and can only be
stored at an address that''s a multiple of 4. In that case, an int*
cannot legally point to an odd address.

The details will vary from one system to another. On some systems, an
int* has a different representation than a char*, and an int* isn''t
even physically capable of pointing to a single byte.

--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

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