clang：没有超出虚拟方法的定义（纯粹的抽象C ++类） [英] clang: no out-of-line virtual method definitions (pure abstract C++ class)

问题描述

我试图使用Clang-3.5编译以下简单的C ++代码：

test.h：

  class A 
 {
 public：
 A（）; 
 virtual〜A（）= 0; 
}; 
  

test.cc：

  #includetest.h
 
 A :: A（）{;} 
 A ::〜A（）{;} 
  

用于编译此命令（Linux，uname -r：3.16.0-4-amd64） p>

  $ clang-3.5 -Weverything -std = c ++ 11 -c test.cc 
  
 
 
 
我得到的错误：
  ./test.h:1:7：warning：'A'没有超出虚拟方法的定义;其vtable将在每个翻译单元中发出[-Wweak-vtables] 
  
任何提示为什么这是发射一个警告？虚拟析构函数根本不内联。恰恰相反，在test.cc.中提供了一个超出行的定义。 
 
 
 
我不认为这个问题是重复的：
 什么意思clang的-Wweak-vtables？ 
 as FilipRoséen建议。在我的问题中，我具体指的是纯抽象类（在建议的副本中没有提到）。我知道 -Wweak-vtables 如何工作与非抽象类，我很好。在我的例子中，我在实现文件中定义析构函数（它是纯抽象的）。这应该防止Clang发出任何错误，即使使用 -Wweak-vtables 。
解决方案
 
 
 
因此，代替
  class A {
 public：
 virtual〜A（）= 0; 
}; 
  
我使用
 code> class A {
 public：
 virtual〜A（）; 
};然后在.cpp文件中实现小型析构函数：
 
 $ b 
 
 
 $ b 
  A ::〜A（）
 {} 
  
 
 b $ b 
这有效地将vtable固定到.cpp文件，而不是在多个翻译单元（对象）中输出它，并成功避免了-Wweak-vtables警告。
 
I'm trying to compile the following simple C++ code using Clang-3.5:

test.h:
class A
{
  public:
    A();
    virtual ~A() = 0;
};
test.cc:
#include "test.h"

A::A() {;}
A::~A() {;}
The command that I use for compiling this (Linux, uname -r: 3.16.0-4-amd64):
$clang-3.5 -Weverything -std=c++11 -c test.cc
And the error that I get:
./test.h:1:7: warning: 'A' has no out-of-line virtual method definitions; its vtable will be emitted in every translation unit [-Wweak-vtables]
Any hints why this is emitting a warning? The virtual destructor is not inlined at all. Quite the opposite, there's a out-of-line definition provided in test.cc. What am I missing here?

Edit 

I don't think that this question is a duplicate of :
What is the meaning of clang's -Wweak-vtables?
as Filip Roséen suggested. In my question I specifically refer to pure abstract classes (not mentioned in the suggested duplicate). I know how -Wweak-vtables works with non-abstract classes and I'm fine with it. In my example I define the destructor (which is pure abstract) in the implementation file. This should prevent Clang from emitting any errors, even with -Wweak-vtables.
解决方案
I ended up implementing a trivial virtual destructor, rather than leaving it pure virtual.

So instead of
class A {
public:
    virtual ~A() = 0;
};
I use
class A {
public:
    virtual ~A();
};
Then implement the trivial destructor in a .cpp file:
A::~A()
{}
This effectively pins the vtable to the .cpp file, instead of outputting it in multiple translation units (objects), and successfully avoids the -Wweak-vtables warning.

                        
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