Linux和macOS都很好，但Windows构建会抛出链接器错误LNK2019

Question

我正在另一个共享库中的共享库中调用类方法。应用程序在Linux和macOS上构建良好但在Windows上我收到：

exportlib.obj：错误LNK2019：未解析的外部符号“__declspec（dllimport）public：class std :: vector> __cdecl Algorithmslib :: k_means（class std :: vector> const＆，unsigned __int64，unsigned __int64）”（__ imp_？k_means @ Algorithmslib @@ QEAA？AV？$ vector @ VPoint @@ V？$ allocator @ VPoint @@@ std @@@ std @@ AEBV23 @ _K1 @ Z）在函数“private：void __cdecl Exportlib :: setSuppPoints（void）”中引用“（？setSuppPoints @ Exportlib @@ AEAAXXZ）debug \ exportlib.dll：致命错误LNK1120：1个未解析的外部

我用尽了可能导致错误的想法（仅限Windows！）

---

Shared library with exported class:

// Project file for exported shared library
// algorithmslib.pro

DEFINES += ALGORITHMSLIB_LIBRARY

根据定义导出或导入：

// algorithmslib_global.h

#if defined(ALGORITHMSLIB_LIBRARY)
#  define ALGORITHMSLIBSHARED_EXPORT Q_DECL_EXPORT
#else
#  define ALGORITHMSLIBSHARED_EXPORT Q_DECL_IMPORT
#endif

舱位声明：

// algorithmslib.h

#include "algorithmslib_global.h"

class ALGORITHMSLIBSHARED_EXPORT Algorithmslib : public QObject
{
    Q_OBJECT

public:
    Algorithmslib();
    std::vector<Point> k_means(const std::vector<Point>& data,
                               size_t k,
                               size_t number_of_iterations);
};

---

Calling k_means method of exported class from within another shared library:

// This is a second shared library which calls the exported class of the 1st shared library
// exportlib.cpp

#include "algorithmslib.h"

void Exportlib::setSuppPoints()
{
    Algorithmslib algorithmEngine;
    std::vector<Point> means = algorithmEngine.k_means(data, k, number_of_iterations);
}

---

我正在使用Desktop_Qt_5_12_1_MSVC2017_64bit-Debug工具包进行编译：

---

我将共享库重命名为非常独特的东西，但是抛出了相同的链接器错误。因此，this issue不是我的情况

Answer 1

First shared lib

我在第一个共享库中有一个struct：

// algorithmslib.h

struct Point {
    float x{0}, y{0}, z{0};
};

Second shared lib

我在我的第二个共享库中使用上面的struct，如下所示：

标题：

// exportlib.h

class Point; // Note that I was using "class" here 
             // but the declaration inside algorithmslib.h is "struct"

size_t computeNumberOfClusters(const std::vector<Point> &data);

资源：

//exportlib.cpp

#include "algorithmslib.h"

std::vector<Point> data(number_of_points); // Point structure is declared in algorithmslib.h

size_t k = computeNumberOfClusters(data);
size_t number_of_iterations = 300;
Algorithmslib algorithmEngine;

std::vector<Point> means = algorithmEngine.k_means(data, k, number_of_iterations);

Fix

我将第二个共享库的标题从class Point;更改为struct Point;，并且Windows上的链接器错误得到了解决：

// exportlib.h

struct Point; // declared in algorithmslib.h as "struct" NOT "class"