c++ - 这是否使用与此 typedef 相同的函数类型(不是指针)的别名

Question

这些是一样的吗？

using on_receipt = void (const string);

typedef void on_receipt(const string);

这些不是函数指针的别名，而是实际的函数类型。他们都编译得很好。看起来奇怪的是 typedef 版本至少有函数名称的占位符，但由于 using 将此占位符移动到 =，没有将返回值和参数分开，这看起来可能不正确或具有误导性。

Answer 1

是的，他们是:

[dcl.typedef]

2 A typedef-name can also be introduced by an alias-declaration. The identifier following the using keyword becomes a typedef-name and the optional attribute-specifier-seq following the identifier appertains to that typedef-name. It has the same semantics as if it were introduced by the typedef specifier. In particular, it does not define a new type.

Live Example

#include <string>
#include <type_traits>

int main()
{
    using on_receipt1 = void (const std::string);    
    typedef void on_receipt2(const std::string);
    static_assert(std::is_same<on_receipt1, on_receipt2>::value, "");
}