C ++ 11成员初始化列表模糊性 [英] C++11 member initialization list ambiguity

问题描述

由于此环境中的GNU标准库实现，我在尝试在c ++ 11符号解析中出现歧义：

• Arch Linux 4.2.5-1（x86_64）


• g ++ 5.2.0


• clang ++ 3.7.0
b

示例：

  #include< iostream& 
 #include< string> 
 
结构版本{
 
无符号专业; 
 unsigned minor; 
 unsigned patch; 
 
版本（unsigned major，unsigned minor，unsigned patch）：
 major（major），minor（minor），patch（patch）{} 
 
 friend std :: ostream& operator<<<（std :: ostream& out，version const& v）{
 out< v.major<< 。 
 out<< v.minor < 。 
 out<< v.patch; 
 return out; 
} 
 
}; 
 
 int main（int argc，char ** argv）{
 version v（1,1,0）; 
 std :: cout<< v<< std :: endl; 
 return 0; 
} 
  

编译器错误：

 错误：成员初始化程序'gnu_dev_major'未命名非静态数据
成员或基类
错误：成员初始化程序'gnu_dev_minor'静态数据
成员或基类
  

命令：

  clang ++ -std = c ++ 11 -o test * .cpp 
  

范围解析运算符似乎不适用于成员初始化列表，因此我无法弄清楚如何解决歧义。

解决方案

另一种方法是使用大括号：

 版本（unsigned major，unsigned minor，unsigned patch）：
 major {major}，minor {minor}，patch {patch} {} 
  

然后宏不会干扰，因为它们是类函数宏，需要调用括号。 / p>

I am struggling with what appears to be an ambiguity in c++11 symbol resolution due to the GNU standard library implementation in this environment:

• Arch Linux 4.2.5-1 (x86_64)
• g++ 5.2.0
• clang++ 3.7.0

Example:

#include <iostream>
#include <string>

struct version {

  unsigned major;
  unsigned minor;
  unsigned patch;

  version(unsigned major, unsigned minor, unsigned patch) :
    major(major), minor(minor), patch(patch) { }

  friend std::ostream & operator<<(std::ostream & out, version const& v) {
    out << v.major << ".";
    out << v.minor << ".";
    out << v.patch;
    return out;
  }

};

int main(int argc, char ** argv) {
  version v(1, 1, 0);
  std::cout << v << std::endl;
  return 0;
}

Compiler error:

error: member initializer 'gnu_dev_major' does not name a non-static data
  member or base class
error: member initializer 'gnu_dev_minor' does not name a non-static data
  member or base class

Command:

clang++ -std=c++11 -o test *.cpp

The scope resolution operator does not appear to be applicable in member initialization lists so I can't figure out how to resolve the ambiguity. This sample compiles fine without the c++11 flag.

解决方案

Another way is to use braces:

version(unsigned major, unsigned minor, unsigned patch) :
  major{major}, minor{minor}, patch{patch} { }

Then the macros will not interfere because they are function-like macros and need parentheses to be invoked.

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