函数样式转换与构造函数 [英] Function-style cast vs. constructor

问题描述

我在C ++中了解到了

I learned that in C++,

typedef foo* mytype;

(mytype) a        // C-style cast

和

mytype(a)         // function-style cast

做同样的事情.

但是我注意到函数样式强制转换与构造函数共享相同的语法.是否存在不明确的情况，我们不知道它是强制转换还是构造函数?

But I notice the function-style cast share the same syntax as a constructor. Aren't there ambiguous cases, where we don't know if it is a cast or a constructor?

char s [] = "Hello";
std::string s2 = std::string(s);     // here it's a constructor but why wouldn't it be ...
std::string s3 = (std::string) s;    // ... interpreted as a function-style cast?

推荐答案

从语法上讲，它始终是强制转换.该强制转换可能恰好调用了一个构造函数:

Syntactically, it is always a cast. That cast may happen to call a constructor:

char s [] = "Hello";
// Function-style cast; internally calls std::basic_string<char>::basic_string(char const*, Allocator)
std::string s2 = std::string(s);
// C-style cast; internally calls std::basic_string<char>::basic_string(char const*, Allocator)
std::string s3 = (std::string) s;

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