C样式的强制转换与函数样式的强制转换相同吗? [英] Is a C-style cast identical to a function-style cast?

问题描述

从

函数样式案例与C样式强制转换有何不同?或者，如果它们相同，是否是Resharper中的bug，它也应该发出警告? int(d)使用安全吗?它看起来比建议的 static_cast< int>(d); .

简单得多.

解决方案

我没有标准的引号，但是cppreference通常就足够了.

显式类型转换

函数强制转换表达式由一个简单的类型说明符或一个typedef说明符组成(换句话说，一个单词类型名称: unsigned int(expression)或 int *(expression)无效)，然后在括号中使用单个表达式.此强制转换表达式与相应的C样式强制转换表达式完全相同.

对于Resharper来说， C ++ cast 可能包含功能转换，因为仅在C ++中有效.

您在问题中链接的答案说明了功能强制转换的安全性.在您的情况下， int(d)应该等效于 static_cast< int>(d).但通常来说，C样式或函数类型的转换是不安全的，因为它们在某些情况下可能等同于 reinterpret_cast ，例如(double *)some_int_ptr .

From this answer to the question "When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?":

C-style cast and function-style cast are casts using (type)object or type(object), respectively.

It then begins to list the behavior of the C-style cast, but never tells whether the function-style cast is identical or not.

I'm asking because Resharper for C++ warns me in case of C-style casts but does not warn me in case of function-style casts:

In what way is the the function-style case different from the C-style cast? Or, if they are identical, is it a bug in Resharper and it should emit a warning, too? Is int(d) safe to use? It looks much simpler than the suggested static_cast<int>(d);.

解决方案

I don't have a quote from the standard, but cppreference is usually good enough.

Explicit type conversion

The functional cast expression consists of a simple type specifier or a typedef specifier (in other words, a single-word type name: unsigned int(expression) or int*(expression) are not valid), followed by a single expression in parentheses. This cast expression is exactly equivalent to the corresponding C-style cast expression.

As for Resharper, it's possible that to it C++ cast includes a functional cast, as that is only valid in C++.

The answer you linked in your question explains how safe a functional cast is. In your case int(d) should be equivalent to static_cast<int>(d). But in general a C-style or functional cast are unsafe as they can be equivalent to reinterpret_cast in certain situations, e.g. (double*)some_int_ptr.

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