未解析的外部符号 "std::atomic_fetch_add"

Question

考虑这个简单的代码：

#include <iostream>
#include <atomic>

void add(std::atomic<double> & a, double c)
{
    std::atomic_fetch_add(&a, c);
}

int main()
{
    std::atomic<double> a;

    a.store(0);
    std::cout << a.load() << std::endl;

    add(a, 5.0);
    std::cout << a.load() << std::endl;

    std::cin.get();
}

编译它会导致：

error LNK2019: unresolved external symbol "double __cdecl std::atomic_fetch_add(struct std::atomic *,double)" (??$atomic_fetch_add@N@std@@YANPAU?$atomic@N@0@N@Z) referenced in function "void __cdecl add(struct std::atomic &,double)" (?add@@YAXAAU?$atomic@N@std@@N@Z)

根据this，atomic_fetch_add在<atomic>中定义，那么发生了什么？

Answer 1

如documentation所述：

The standard library provides specializations of the std::atomic template for the following types:

和 double 不在列表中。非成员函数也有注释：

There are non-member function template equivalents for all member functions of std::atomic. Those non-member functions may be additionally overloaded for types that are not specializations of std::atomic, but are able to guarantee atomicity. The only such type in the standard library is std::shared_ptr.

所以不支持double。

未解析的外部符号 "std::atomic_fetch_add"

unresolved external symbol "std::atomic_fetch_add"

c++

atomic