将结构转换为int [英] Casting a structure to an int
问题描述
我最近遇到了以下CAST宏，它可以向任何其他东西投射任何
：
#define CAST（new_type，old_object）（* （（new_type *）& old_object））
union
{
char ch [4];
int i [2];
} my_union;
long longvar;
longvar = （长）my_union;非法演员
////////////////非法
longvar = CAST（长，my_union）;合法演员
我理解为什么CAST宏有效，但我无法理解
以下演员的问题是什么：
longvar =（长）my_union;
有人可以告诉我上面的
投射机制有什么问题？
PS这不是作业。我从以下
链接中获取此代码：
http://paul.rutgers.edu/~rhoads/Code/cast_anything.c
I recently came across the following CAST macro which can cast anything
to any other thing:
#define CAST(new_type,old_object) (*((new_type *)&old_object))
union
{
char ch[4];
int i[2];
} my_union;
long longvar;
longvar = (long)my_union; Illegal cast
//////////////// ILLEGAL
longvar = CAST(long, my_union); Legal cast
I understands that why the CAST macro works but I cannot understands
that what is the problem in the following casting :
longvar = (long)my_union;
Can somebody please tell me that what is the problem in the above
casting mechanism?
PS This is not an assignment. I took this code from the following
link:
http://paul.rutgers.edu/~rhoads/Code/cast_anything.c
推荐答案
你好，
见插入的评论：
ca ******** @ yahoo.com 写道：
我最近遇到了以下CAST宏，它可以向任何其他东西施放任何东西：
#define CAST（new_type，old_object）（*（（new_type *）& old_object））
联盟
{ch /> char ch [4] ;
int i [2];
} my_union;
long longvar;
longvar =（long）my_union;非法演员
//////////////// ILLEGAL
my_union的大小？和sizeof of long？
longvar = CAST（long，my_union）;合法演员
我理解为什么CAST宏有效，但我无法理解下面的演员有什么问题：
longvar =（long）my_union ;
有人可以告诉我上面的演员机制有什么问题吗？
PS这不是作业。我从以下
链接中获取此代码：
http://paul.rutgers.edu/~rhoads/Code/cast_anything.c
I recently came across the following CAST macro which can cast anything
to any other thing:
#define CAST(new_type,old_object) (*((new_type *)&old_object))
union
{
char ch[4];
int i[2];
} my_union;
long longvar;
longvar = (long)my_union; Illegal cast
//////////////// ILLEGAL
Sizeof of my_union? and sizeof of long?
longvar = CAST(long, my_union); Legal cast
I understands that why the CAST macro works but I cannot understands
that what is the problem in the following casting :
longvar = (long)my_union;
Can somebody please tell me that what is the problem in the above
casting mechanism?
PS This is not an assignment. I took this code from the following
link:
http://paul.rutgers.edu/~rhoads/Code/cast_anything.c
抛出任何东西或任何东西的第一个字节甚至所有它和一些
部分谁知道什么。实用，美观，危险。
亲切的问候。
"cast anything or the first bytes of anything or even all it and some
parts of who knows what". Practical, nice and dangerous.
Kind regards.
ca ******** @ yahoo.com 写道：
我最近遇到了以下CAST宏，它可以投
#define CAST（new_type，old_object）（*（（new_type *）& old_object））
I recently came across the following CAST macro which can cast anything
to any other thing:
#define CAST(new_type,old_object) (*((new_type *)&old_object))
一个不应该做的事情的完美例子。
A perfect example of what shouldn''t be done.
ca ******** @ yahoo.com 写道：
ca********@yahoo.com writes:
我理解为什么CAST宏工作但我无法理解
以下演员中的问题是什么：
longvar =（long）my_union;
I understands that why the CAST macro works but I cannot understands
that what is the problem in the following casting :
longvar = (long)my_union;
在演员表达式中，表达式的值必须使用标量类型，但是联合不是标量类型。 （标量
类型是算术类型或指针类型。）
-
我应该杀死你，你站在哪里，没有价值的人。 --Kaz
In a cast expression, the expression whose value is cast must
have a scalar type, but a union is not a scalar type. (A scalar
type is an arithmetic type or a pointer type.)
--
"I should killfile you where you stand, worthless human." --Kaz
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