f***t
发帖数: 25 | 1 对于简单类型的const_cast，下面代码：
int const i=2; //现在i值const了
int* k = const_cast(&i); //用引用也行，结果是一样的
*k=3; //借被const cast 的k改i值；成功；
cout<
cout<<*k<
cout<<&i<
cout<
以上是VC6的编译。
把简单类型换成类就不会有这种现象，这是不是VC6的一个bug? |
t****t
发帖数: 6806 | 2 it's undefined to modify a const value, no matter what method you use.
in other words, if a value is declared as const, you can NOT change it. if
you change it, it's undefined (means: wierd things happen).
【在 f***t 的大作中提到】
: 对于简单类型的const_cast，下面代码：
: int const i=2; //现在i值const了
: int* k = const_cast(&i); //用引用也行，结果是一样的
: *k=3; //借被const cast 的k改i值；成功；
: cout<: cout<<*k<: cout<<&i<: cout<: 以上是VC6的编译。
: 把简单类型换成类就不会有这种现象，这是不是VC6的一个bug?
|
f***t
发帖数: 25 | 3 Thanks，这个解释说的通.
不过，当时c++设计这种cast的动机，不就是为了改const的值吗？
【在 t****t 的大作中提到】
: it's undefined to modify a const value, no matter what method you use.
: in other words, if a value is declared as const, you can NOT change it. if
: you change it, it's undefined (means: wierd things happen).
|
l*********s
发帖数: 5409 | 4 Not really ; it is explained in Effective C++
【在 f***t 的大作中提到】
: Thanks，这个解释说的通.
: 不过，当时c++设计这种cast的动机，不就是为了改const的值吗？
|
t****t
发帖数: 6806 | 5 no, it's designed to change value referenced by const pointer/reference, but
itself not const. const value is never meant to be changed.
【在 f***t 的大作中提到】
: Thanks，这个解释说的通.
: 不过，当时c++设计这种cast的动机，不就是为了改const的值吗？
|
A**u
发帖数: 2458 | 6 哇
你的c++功力真是令我太崇拜啦
but
【在 t****t 的大作中提到】
: no, it's designed to change value referenced by const pointer/reference, but
: itself not const. const value is never meant to be changed.
|
f***t
发帖数: 25 | 7 i c. 多谢大牛！
but
【在 t****t 的大作中提到】
: no, it's designed to change value referenced by const pointer/reference, but
: itself not const. const value is never meant to be changed.
|
t*******c
发帖数: 288 | 8 check out this:
http://en.cppreference.com/w/cpp/language/const_cast
The reference code has the same error as yours. As stated in Note, "Even
though const_cast may remove constness from any pointer or reference, using
the resulting pointer or reference to write to an object that was declared
const invokes undefined behavior." |
