指针和整数 [英] pointers and integers
问题描述
我有一个与指针/整数转换有关的问题。
在阅读了这个新闻组的各种线程后，我发现
指针/整数转换不可移植，可能导致
即使在同一平台上也未定义结果。我只是好奇
知道为什么会这样？一个明显的原因是
指针变量的大小可能与整数变量不一样。
其他原因可能是什么？
考虑一个实现，其中指针和整数变量
都是*相同*大小（比如4个字节）。
在这样的平台上，可以是整数/指针转换原因
任何未定义的结果？为什么？
例如。考虑下面这段代码：
int main（无效）
{
int * ptr_i;
int value = 0x100; / *我想访问位置0x100
内存* /
ptr_i = value;
}
假设sizeof（int *）等于sizeof（int）。
ptr_i = value可能会出现什么问题？可能导致？
转换后的价值到ptr_i，是否可能
ptr_i总共包含一个不同的值？
I have a question related to pointer/integer conversion.
After reading various threads on this newsgroup I found that
pointer/integer conversion is not portable and may lead to
undefined results even on the same platform. I was just curious
to know why is it so ? One obvious reason is that size of
pointer variable might not be the same as integer variable.
What could be the other reasons ?
Consider an implementation where pointers and integer variables
are all of *same* size (say 4 bytes).
On such a platform, can the integer/pointer conversion cause
any undefined results ? Why ?
For eg. Consider the following piece of code:
int main (void)
{
int * ptr_i ;
int value = 0x100; /* I want to access location 0x100 in
memory */
ptr_i = value;
}
Assume sizeof(int *) is equal to sizeof(int).
What sort of problems could the "ptr_i = value" may lead to ?
After the conversion of "value" to "ptr_i", is it possible
that "ptr_i" contain altogether a different value ?
推荐答案
当指针和整数大小相同时你需要
应该能够将指针转换为整数，而不会出现任何问题。
但是由于
$ b，这不是推荐的做法$ b便携性，代码可读性和可靠性问题。
-
EventStudio 2.5 - http://www.EventHelix.com/EventStudio
以纯文本格式输入模型;以PDF和Word格式生成调用流程
When the pointer and the integer are of the same size you
should be able to convert a pointer to an integer without
any problem.
However it is not a recommended practice due to
portability, code readability and reliability concerns.
--
EventStudio 2.5 - http://www.EventHelix.com/EventStudio
Enter model in plain text;generate call flow in PDF and Word
你怎么知道内存位置0x100可供使用。
How do you know memory location 0x100 is available for using.
< a href =mailto：ju ********** @ yahoo.co.in> ju ********** @ yahoo.co.in 写道：
我有一个与指针/整数转换有关的问题。
读完这个newsgro上的各种线程后我发现
指针/整数转换不可移植，即使在同一平台上也可能导致未定义的结果。我很好奇
知道为什么会这样？一个显而易见的原因是指针变量的大小可能与整数变量的大小不同。
其他原因可能是什么？
考虑指针和整数变量的实现
都是*相同*大小（比如4个字节）。
在这样的平台上，整数/指针转换是否会导致任何未定义的结果？为什么？
例如。请考虑以下代码：
int main（void）
{int / ptr_i;
int value = 0x100; / *我想在内存中访问位置0x100 * /
ptr_i = value;
}
I have a question related to pointer/integer conversion.
After reading various threads on this newsgroup I found that
pointer/integer conversion is not portable and may lead to
undefined results even on the same platform. I was just curious
to know why is it so ? One obvious reason is that size of
pointer variable might not be the same as integer variable.
What could be the other reasons ?
Consider an implementation where pointers and integer variables
are all of *same* size (say 4 bytes).
On such a platform, can the integer/pointer conversion cause
any undefined results ? Why ?
For eg. Consider the following piece of code:
int main (void)
{
int * ptr_i ;
int value = 0x100; /* I want to access location 0x100 in
memory */
ptr_i = value;
}
如果你知道你想要在内存中访问位置0x100，
然后你没有处理便携式代码的情况，
所以为什么要担心这些代码的可移植性？
-
pete
If you know that you want to access location 0x100 in memory,
then you''re not dealing with a portable code situation,
so why worry about portability of such code?
--
pete
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