問題描述

這是一個非常簡單的問題.考慮以下代碼:

This is a very simple question. Consider the following code:

#include <iostream>
#include <memory>

typedef std::unique_ptr<void> UniqueVoidPtr;

int main() {
    UniqueVoidPtr p(new int);
    return 0;
}

使用 cygwin (g++ 4.5.3) 和以下命令編譯 g++ -std=c++0x -o prog file.cpp 工作得很好.但是，使用 Microsoft 編譯器(VS 2010 或 2013)進行編譯時出現此錯誤:

Compiling with cygwin (g++ 4.5.3) with the following command g++ -std=c++0x -o prog file.cpp works just fine. However, compiling with the microsoft compiler (either VS 2010 or 2013) I get this error:

C:Program Files (x86)Microsoft Visual Studio 10.0VCINCLUDEmemory(2067) : error C2070: 'void': illegal sizeof operand
        C:Program Files (x86)Microsoft Visual Studio 10.0VCINCLUDEmemory(2066) : while compiling class template member function 'void std::default_delete<_Ty>::operator ()(_Ty *) const'
        with
        [
            _Ty=void
        ]
        C:Program Files (x86)Microsoft Visual Studio 10.0VCINCLUDE	ype_traits(650) : see reference to class template instantiation 'std::default_delete<_Ty>' being compiled
        with
        [
            _Ty=void
        ]
        C:Program Files (x86)Microsoft Visual Studio 10.0VCINCLUDEmemory(2193) : see reference to class template instantiation 'std::tr1::is_empty<_Ty>' being compiled
        with
        [
            _Ty=std::default_delete<void>
        ]
        foo1.cpp(7) : see reference to class template instantiation 'std::unique_ptr<_Ty>' being compiled
        with
        [
            _Ty=void
        ]

這是預期的嗎?我正在寫一個類，我想在類中擁有一個唯一的指針.在嘗試為類計算移動構造函數的語義時，我遇到了這個問題(我假設是因為我最終正確編碼了移動構造函數:即其他錯誤已修復).

Is this expected? I'm writing a class where I wanted to have a unique pointer in the in the class. While trying to work out the semantics of a move constructor for the class, I ran into this (I assume because I finally got my move constructor coded correctly: i.e. the other errors were fixed).

推薦答案

MSVC 是對的，而 GCC 是錯的:

MSVC is right while GCC is wrong:

標準(3.9/5):

不完全定義的對象類型和void類型是不完全類型

Incompletely-defined object types and the void types are incomplete types

標準(20.7.1.1.2/4):

Standard(20.7.1.1.2/4):

如果 T 是不完整類型，則程序格式錯誤

If T is an incomplete type, the program is ill-formed

這篇關于應該 std::unique_ptr<void>被允許的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！