blocks|key|1210577|text|由于有许多不同类型的类型转换，每种类型都有不同的语义，static_cast<>允许您说“我正在进行从一种类型到另一种类型的合法转换”，就像从整型转换为双精度类型一样。一个普通的C风格的类型转换可以意味着很多事情。你是向上/向下投射吗？你在重新解释一个指针吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1210578|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Since there are many different kinds of casting each with different semantics, static_cast&lt;> allows you to say "I'm doing a legal conversion from one type to another" like from int to double. A plain C-style cast can mean a lot of things. Are you up/down casting? Are you reinterpreting a pointer?

blocks|key|1210639|text|C%2B%2B样式转换由编译器检查。C风格的类型转换不是，而且可能在运行时失败。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1210640|此外，可以很容易地搜索到c%2B%2B风格的类型转换，而搜索c风格的类型转换却非常困难。|1210641|另一个很大的好处是，4种不同的C%2B%2B风格转换更清楚地表达了程序员的意图。|1210642|在编写C%2B%2B时，我几乎总是使用C%2B%2B风格，而不是C风格。|1210643|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|L|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|M|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

C++ style casts are checked by the compiler. C style casts aren't and can fail at runtime.

Also, c++ style casts can be searched for easily, whereas it's really hard to search for c style casts.

Another big benefit is that the 4 different C++ style casts express the intent of the programmer more clearly. 

When writing C++ I'd pretty much always use the C++ ones over the the C style.

blocks|key|1425562|text|struct+A+{};
struct+B+:+A+{};
struct+C+{};+

int+main()
{
++++A*+a+=+new+A;++++

++++int+i+=+10;

++++a+=+(A*)+(&i);+//+NO+ERROR!+FAIL!

++++//a+=+static_cast<A*>(&i);+ERROR!+SMART!

++++A*+b+=+new+B;

++++B*+b2+=+static_cast<B*>(b);+//+NO+ERROR!+SMART!

++++C*+c+=+(C*)(b);+//+NO+ERROR!+FAIL!

++++//C*+c+=+static_cast<C*>(b);+ERROR!+SMART!
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1425563|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>struct A {};
struct B : A {};
struct C {}; 

int main()
{
 A* a = new A; 

 int i = 10;

 a = (A*) (&amp;i); // NO ERROR! FAIL!

 //a = static_cast&lt;A*&gt;(&amp;i); ERROR! SMART!

 A* b = new B;

 B* b2 = static_cast&lt;B*&gt;(b); // NO ERROR! SMART!

 C* c = (C*)(b); // NO ERROR! FAIL!

 //C* c = static_cast&lt;C*&gt;(b); ERROR! SMART!
}
</code></pre>

blocks|key|1210696|text|static_cast在编译时检查转换不是在明显不兼容的类型之间进行的。与dynamic_cast相反，在运行时不会检查类型兼容性。此外，static_cast转换不一定是安全的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1210697|static_cast用于从指向基类的指针转换为指向派生类的指针，或者在本机类型之间进行转换，例如枚举到整型或浮点型到整型。|1210698|static_cast的用户必须确保转换是安全的。|1210699|C风格的强制转换不执行任何检查，无论是在编译时还是在运行时。|1210700|entityMap^0|0|B|11|C|1X|B|0|0|B|0|0|B|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|M|$]]

<code>static_cast</code> checks at compile time that conversion is not between obviously incompatible types. Contrary to <code>dynamic_cast</code>, no check for types compatibility is done at run time. Also, <code>static_cast</code> conversion is not necessarily safe.

<code>static_cast</code> is used to convert from pointer to base class to pointer to derived class, or between native types, such as enum to int or float to int. 

The user of <code>static_cast</code> must make sure that the conversion is safe.

The C-style cast does not perform any check, either at compile or at run time.

Is there any reason to prefer <code>static_cast&lt;&gt;</code> over C style casting? Are they equivalent? Is there any sort of speed difference?

What is the difference between static_cast<> and C style casting?

编译器

有什么理由更喜欢static_cast<>而不是C风格的类型转换吗？它们是等价的吗？有没有速度上的差异？

问static_cast<>和C风格的转换有什么不同？
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