Question

As per title, I m trying to build a DLL using C and link it from a C++ project. I read and followed different tutorials on internet but everytime there is something missing and I don t understand what.

在此,我采取了以下步骤:

我创建了一个新的Win32项目,名为testlib,然后从主人那里选择了“DL”和“Empty Project”。

添加一个标题:

//testlib.h

#include <stdio.h>

__declspec(dllexport) void hello();

添加一个来源;由于我希望它成为一C来文方,我读一读,应该简单地将C.c.的档案改成一。

//testlib.c

#include "testlib.h"

void hello() {
    printf("DLL hello() called
");
}

建设。

现在,我想在另一个项目中利用我的有益助手。

然后: new project (testlibUse). This time I selected "Empty project".
No need to add an header, just created a cpp source

//main.cpp
#include <testlib.h>

int main() {
    hello();
}

然后:

我在册子上添加了一条路:testlib.dll in Property->VC++Directories-> 可执行目录
我在册子上添加了一条路:testlib.h in Property->VC++Directories->IncludeDirectories
我添加了以下途径:房地产和建筑中的“条码”:;Linker->Input->Additional Dependencies

我试图建设,但我犯了一个联系错误:

LINK : C:path estlibUseDebug estlibUse.exe not found or not built by the last incremental link; performing full link
main.obj : error LNK2019: unresolved external symbol "void __cdecl hello(void)" (?hello@@YAXXZ) referenced in function _main
C:path estlibUseDebug estlibUse.exe : fatal error LNK1120: 1 unresolved externals

如果我回到<条码>测试lib,更名为<条码>测试lib.c,载于<条码>测试校准/代码>,并重建票价,那么,我可以建造<条码>测试校准/代码>,但我在操作时有“没有发现”错误。

I tried also to change the configurations of both projects in "Release" (changing the path where needed), but nothing changed.

Sorry for the long post but I think it was necessary to write down exactly what I did.

任何建议?

此外,如果我想要在Qt项目中使用我的飞机,我是否需要改变配置参数吗?

Answer 1

You have several problems:

The header file should mark the functions as exported when being compiled in the DLL but imported when being compiled by a library user.
The header file should wrap the function declarations in an extern "C" block when being compiled as C++ to ensure that the names do not get mangled
The DLL is not on your executable s library search path, so it can t be found at runtime.

为了确定第(1)和(2)条,把你的头盔改成:

#ifdef __cplusplus
extern "C" {
#endif

// Assume this symbol is only defined by your DLL project, so we can either
// export or import the symbols as appropriate
#if COMPILING_MY_TEST_DLL
#define TESTLIB_EXPORT __declspec(dllexport)
#else
#define TESTLIB_EXPORT __declspec(dllimport)
#endif

TESTLIB_EXPORT void hello();
// ... more function declarations, marked with TESTLIB_EXPORT

#ifdef __cplusplus
}
#endif

更正(3),将《刑法》与你的可起诉档案翻一番。 http://msdn.microsoft.com/en-us/library/7d83bc 1828v=vs.80%29.aspx>MS<0/a>,详细描述如何搜寻DLs。你的最佳解决办法是把你的DLL复制到你可起诉的档案馆。你们要么能够以人工的方式这样做,要么在你的项目中增加一个在后实施的步骤,对你们来说就是这样。

Answer 2

页: 1 包括:

extern "C" {
    #include <testlib.h>
}

Answer 3

它看一看需要确保汇编者不使用mangle 。您应当能够在测试性定义中添加一个<代码>extern “C”:

#ifdef __cplusplus
extern "C"
#endif
__declspec(dllexport) void hello();

Answer 4

此处采用C++可包含的贵方档案方法。确保在< 预处理环境内建立<>TESTLIB_EXPORTS。在包括该船长使用DLL的项目中,船长将宣布这些功能为进口而不是出口。

<代码>cplus 警卫将告诉编辑人员使用C国名勋章而不是C++国名校正来进口你的职能。

#include <stdio.h>

#ifdef TESTLIB_EXPORTS
#define TESTLIB_API __declspec(dllexport)
#else
#define TESTLIB_API __declspec(dllimport)
#endif

#ifdef __cplusplus
extern "C" {
#endif

TESTLIB_API void hello();
/* other prototypes here */

#ifdef __cplusplus
}
#endif

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