如何在Windows 10 Visual Studio中使用必需的.dll进行构建

Question

I'm trying to build a project. I have a.lib file that I need to use in my project. I know that there are two ways to use this lib:

• add it using #pragma comment(lib, "a.lib")
• add it to linker dependencies Configuration Properties -> Linker -> Input -> Additional Dependencies

Now, a.lib uses StackWalk64 function DbgHelp . This library is supplied as DbgHelp.lib and DbgHelp.dll . I know that I can use it as a lib using two ways listed above. But what if I don't want to include it into my project and want to use DbgHelp.dll , how can I do that in Visual Studio?

Answer 1

If you want to call a function that is within a DLL, but don't want to link to the LIB file that imports these functions for you, then you can use LoadLibrary and GetProcAddress . (Though if you have the import library and can link to it, why do you want to load these functions manually?)

IF YOU HAVE THE DbgHelp.lib IMPORT LIBRARY, USE IT! LOADING FUNCTIONS MAUNALLY IS ERROR-PRONE IF NOT DONE RESPONSIBLY. USE WITH CAUTION!

// Type definition for a function pointer that can call the function
typedef BOOL (WINAPI *StackWalk64_func)
(
    DWORD,
    HANDLE,
    HANDLE,
    LPSTACKFRAME64,
    PVOID,
    PREAD_PROCESS_MEMORY_ROUTINE64,
    PFUNCTION_TABLE_ACCESS_ROUTINE64,
    PGET_MODULE_BASE_ROUTINE64,
    PTRANSLATE_ADDRESS_ROUTINE64
);

// Within a function . . .

HMODULE hDbgHelpDll = LoadLibrary(TEXT("DbgHelp.dll"));
if (hDbgHelpDll == NULL)
{
    // handle error and return
}

StackWalk64_func funStackWalk64
    = (StackWalk64_func)GetProcAddress(hDbgHelpDll, "StackWalk64");

if (funStackWalk64 == NULL)
{
    // handle error and return
}

// funStackWalk64 is valid and ready to use

Now you can call funStackWalk64 like the function StackWalk64 , and pass the function pointer around the place. When you're done using the library, you should free the module handle:

FreeLibrary(hDbgHelpDll);

Answer 2

Usually (and in Visual C++ specifically,) the lib file that comes with a dll is what is called an "import library". It means that the library has no actual function bodies in it; it is just there to appease the linker and instruct it to generate an EXE (or DLL) that would use the first dll at load time .

It is so in this case too. Since you don't have access to the source code for DbgHelp so that you can build it as a real static library, you need to make do with the small import library at link time and the dll file at load/run time.

Note: the whole linking and dynamic linking concepts and mechanisms are obviously a lot more complex than what I have room here to discuss. So, the explanation above is quite narrow and specific to your question.

Answer 3

Please read up: http://www.learncpp.com/cpp-tutorial/a1-static-and-dynamic-libraries/

Implicit Linkage with an import library (using .lib)

In this case the static-library is an "import library" , which automates the process of determining the effective functions in the DLL. This is called implicit dynamic linkage .

Explicit Linkage

If you don't want to use the import library you have to determine all functions by yourself, create corresponding pointers to the addresses of the procedures and use them after that. Usually there's some InitDLL() function in your client code, which does this.

See: https://msdn.microsoft.com/de-de/library/64tkc9y5.aspx

The "GetProcAddress"-function can be used to obtain a handle to the function and call it.

This is called explicit dynamic linkage and requires also the calls to LoadLibrary() and FreeLibrary() on Windows.

More Info: http://www.equestionanswers.com/dll/what-is-implicit-and-explicit-linking-in-dynamic-loading.php

Explicit Linkage on Linux

For linux/unix things work differently. If you want to read up: http://www.yolinux.com/TUTORIALS/LibraryArchives-StaticAndDynamic.html