相关疑难解决方法(0)

以下代码无法链接:

#include <atomic>                                                                                                                                                             
struct A
{
    unsigned long a;
    unsigned long b;
};                                                                                                                                                           
struct B
{
    void set(A tmp)
    {
        _a.store(tmp);
    }
    std::atomic<A> _a;
 };                                                                                                                                                           

 int main()
{
   B b;
   b.set(A());
   return  0;
}

出现以下错误:

/tmp/cc8gyaZM.o: In function `std::atomic<A>::store(A, std::memory_order)':
dryn.cpp:     (.text._ZNSt6atomicI1AE5storeES0_St12memory_order[_ZNSt6atomicI1AE5storeES0_St12memory_order]+0x3e): undefined reference to `__atomic_store_16'

如果我用大小为int的任何东西替换unsigned long-s,那么编译就好了.使用g ++ 4.7.2.你知道为什么会这样吗？

用命令编译:

g++ dryn.cpp --std=c++11

我遇到这个编译错误

function std::atomic::is_lock_free() const: error: undefined reference 
to '__atomic_is_lock_free' 

在Linux上使用gcc 4.7.2编译代码如下所示.

struct S {
  int a;
  int b;
};


  std::atomic<S> s;
  cout << s.is_lock_free() << endl;

众所周知:https://stackoverflow.com/a/32694707/1558037

页面1104:http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3337.pdf

C++11§29.5/ 1说

有一个泛型类模板atomic.模板参数T的类型应该是可以轻易复制的(3.9).

§3.9告诉

标量类型,平凡可复制类类型(第9节),此类类型的数组以及这些类型的cv限定版本(3.9.3)统称为平凡可复制类型.

全文:

1 There is a generic class template atomic<T>. The type of the template argument T shall be trivially copyable (3.9). [ Note: Type arguments that are not also statically initializable may be difficult to use.
— end note ]
2 The semantics of the operations on specializations of atomic are defined in 29.6. 
3 Specializations and instantiations of the atomic template shall have a deleted copy …