我将C ++类实现为DLL。但是当我连接到dll时出现链接器错误。我有正确的设置,不确定什么地方出了问题。我进行了研究,但找不到相关的解决方案,因此提出了查询。
ASM_Lib.h
#ifdef EXPORT
#define DLLCLASS __declspec(dllexport)
#else
#define DLLCLASS __declspec(dllimport)
#endif
class ASM
{
public:
ASM();
~ASM();
int loadData(string path, string ext);
int landmarkEqualization();
private:
vector<PtsData_<CurrentType_>> pts;//this vector size is same as number of images, released after use
vector<string> files;//file names
vector<TrainingData_<CurrentType_>> td;//this vector size is same as number of images, released after use
vector<Mat> images;
};
extern "C" /*Important for avoiding Name decoration*/
{
DLLCLASS ASM* _cdecl CreateASMObject();
};
// Function Pointer Declaration of CreateASMObject() [Entry Point Function]
typedef ASM* (*CREATE_ASM) ();
ASM_Lib.cpp
namespace VIDEO_ANALYTICS_PLATFORM{
DLLCLASS ASM* _cdecl CreateASMObject() {
return new ASM();
}
ASM::ASM()
{
}
ASM::~ASM()
{
}
int ASM::loadData(string path, string ext)
{
return FILE_READ_WRITE_ERROR;
}
///*
//This loop equalize all landmark points to
//be equal distances
//*/
int ASM::landmarkEqualization()
{
//Clear vector
pts.clear();
vector<PtsData_<CurrentType_>>().swap(pts);
return SUCCESS;
}
}
然后在我的测试程序中,我以
#include "stdafx.h"
#include <iostream>
#include "ASM_Lib.h"
using namespace VIDEO_ANALYTICS_PLATFORM;
int _tmain(int argc, _TCHAR* argv[])
{
HINSTANCE hDLL = LoadLibrary(L"ASM_Lib.dll");
if (hDLL == NULL){
std::cout << "Failed to load library.\n";
}else{
CREATE_ASM pEntryFunction = (CREATE_ASM)GetProcAddress(hDLL, "CreateASMObject");
ASM* pASM = pEntryFunction();
if (pASM) {
pASM->loadData("C:\\PointsFiles", "pts");
}
FreeLibrary(hDLL);
}
std::cin.get();
return 0;
}
但是我有LNK2019链接错误(在函数wmain中引用),但是我没有wmain。可能是什么问题呢?
test.obj : error LNK2019: unresolved external symbol "public: int __cdecl VIDEO_ANALYTICS_PLATFORM::ASM::loadData(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?loadData@ASM@VIDEO_ANALYTICS_PLATFORM@@QEAAHV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@0@Z) referenced in function wmain
如果我注释掉此API pASM->loadData("C:\\PointsFiles", "pts");
,则它可以工作并且可以正确加载dll。
编辑:最后更新
ASM_Lib.h
#ifdef EXPORT
#define DLLCLASS __declspec(dllexport)
#else
#define DLLCLASS __declspec(dllimport)
#endif
namespace VIDEO_ANALYTICS_PLATFORM{
class i_ASM
{
public:
virtual ~i_ASM(){ ; };
virtual int loadData(string path, string ext)=0;
virtual int landmarkEqualization() = 0;
};
class ASM : public i_ASM
{
public:
ASM(){ }
int loadData(string path, string ext);
int landmarkEqualization();
private:
vector<PtsData_<CurrentType_>> pts;//this vector size is same as number of images, released after use
vector<string> files;//file names
vector<TrainingData_<CurrentType_>> td;//this vector size is same as number of images, released after use
vector<Mat> images;
};
extern "C"
{
DLLCLASS i_ASM* _cdecl CreateASMObject();
};
}
ASM_Lib.cpp
namespace VIDEO_ANALYTICS_PLATFORM{
DLLCLASS i_ASM* _cdecl CreateASMObject() {
return new ASM();
}
int ASM::loadData(string path, string ext)
{
return 0;
}
///*
//This loop equalize all landmark points to
//be equal distances
//*/
int ASM::landmarkEqualization()
{
//Clear vector
pts.clear();
vector<PtsData_<CurrentType_>>().swap(pts);
return SUCCESS;
}
}
Test.cpp
#include "ASM_Lib.h"
using namespace VIDEO_ANALYTICS_PLATFORM;
int _tmain(int argc, _TCHAR* argv[])
{
ASM* pASM = ::CreateASMObject();
if (pASM) {
pASM->loadData("C:\\PointsFiles", "pts");
pASM->~ASM();
pASM = NULL;
}
return 0;
}
我认为,我的上一次更新应该有效。但对于loadData()
和仍然存在链接器错误LNK2019 ~ASM()
。我在同一解决方案中同时测试了项目和ASM_Lib项目。有什么事吗
DLL仅导出CreateASMObject函数。ASM :: loadData不会导出,而是在测试应用程序中使用。我可以提出2种解决方法:
1)仅使用__declspec(dllexport)属性来分配整个ASM类或loadData成员,然后添加ASM_Lib.lib来测试应用程序项目。
2)声明纯抽象类(接口)IASM并更改CreateASMObject的返回类型:
class IASM
{
public:
virtual ~IASM() = 0;
virtual int loadData(string path, string ext) = 0;
};
extern "C"
{
DLLCLASS IASM* _cdecl CreateASMObject();
};
然后从IASM派生ASM并实现摘要方法(可以在CPP文件中完成)。在这种情况下,链接器不需要loadData方法的地址,因为它将在运行时通过vtable解析。
PS。您必须确保DLL及其客户端使用相同的堆管理器实例(例如,相同版本的C运行时DLL)。否则,调用在另一个模块中创建的对象的delete是不安全的。解决方案是添加一种实现删除的方法:
class IASM
{
public:
virtual void destroy() = 0;
protected:
~IMyAPI() = default;
};
class ASM: public IASM
{
public:
virtual void destroy() override
{
delete this;
}
};
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