Explicitly link DLL [modified]

[shakumar_22]

Hi I want to imort dll through dynamic link in vc++ 6.0. I know static link dll, giving the lib file in projects->setting->link->lib path and Store the dll file in system directory. And by using “using namespace “ we can access all the function in the dll automatically. Now I want to know how to link dll dynamically. There are some example in google search, even I could not understand that. If you give any suggestion (step by step)or any simple example ,its very useful for me. Regards shakumar

shakumar

modified on Thursday, May 22, 2008 5:21 AM

[Rajesh R Subramanian]

DLLs are simple - Part 1 to 4[^] See the DLLs and Assemblies section in this page by Hans Dietrich[^] Also, see DLLs and Assemblies[^] under general programming. Additionally, read in MSDN about LoadLibrary(), GetProcAddress().

Nobody can give you wiser advice than yourself. - Cicero .·´¯`·->Rajesh<-·´¯`·. Codeproject.com: Visual C++ MVP

[Cedric Moonen]

Dll's are always dynamically linked (dll stands for dynamic link library). So what's your question exactly ? Why don't you want to use the static lib provided with the dll ? (BTW this doesn't contain the code of the dll but only information about how to load the dll, basically). You can also use LoadLibrary to load the dll and then use GetProcAddress to retrieve the address of a specific exported function of your dll. But this is a bit more complex. The main advantage is that you can handle the error when the dll is missing the way you want (and not simply have an error message saying that the dll is missing and then exit the program).

Cédric Moonen Software developer
Charting control [v1.4]

[Force Code]

typedef DWORD (*GETNGLYPHS)(HDC hdc,LPCTSTR lpstr,int c,LPWORD pgi,DWORD fl); GETNGLYPHS GetGlyphIndices = (GETNGLYPHS)GetProcAddress(LoadLibrary("gdi32.dll"), "GetGlyphIndicesA"); . . . GetGlyphIndices(hdc,save_chrs,sg_cnt,save_glyphs,1);

[shakumar_22]

Thanks for your reply As i said above ,in my programme I used shell32.dll, I import the dll through project->setting->link->giving lib path ”shell.lib”. it automatically(ctl+tab) it give the function “SHFILEOPSTRUCT.” I want to load dll at runtime ,ie: giving the path of the dll through the code. My doubt was when I loading dll at run time , how can I access the function from dll because at run time only dll will import, so we cannot know what are the function is available in dll. Will all the dll can import(dynamic) like this. It may be simple for u, for me it is not understand, so give u’r suggestion. Regards shakumar

shakumar

[Cedric Moonen]

shakumar_22 wrote:

I want to load dll at runtime

It WILL be loaded at runtime. That's the purpose of the dll. As I said in my previous post, it's not because you link against shell32.lib that you are statically linking. The lib file only contains information about the way to load your dll but your dll will still be loaded at runtime. The only thing you have to make sure is that in your project settings, you choose the runtime library as a dll: (for VC2005) open your project properties -> C/C++ entry -> "Code generation" -> "Runtime Library" and there select "Multi-threaded Debug Dll" (or "Multi-threaded Dll" if you are in release mode).

Cédric Moonen Software developer
Charting control [v1.4]

[Rajesh R Subramanian]

I think he is looking for ways to load the DLL from his program, without the help of a .lib file. That's what I understand. CPMRU is charged, you see. [add] May I know why is this post down-voted. I'll appreciate any feedback. :) [/add]

Nobody can give you wiser advice than yourself. - Cicero .·´¯`·->Rajesh<-·´¯`·. Codeproject.com: Visual C++ MVP

modified on Thursday, May 22, 2008 4:49 AM

[Cedric Moonen]

Yes I got that but for what reason exactly ? I honnestly it will only make things much more complex with no added value in this case. He is talking about a windows dll for which I don't see any reason why you would load it explicitely. (and I also already gave him an answer if he really wants to do load it explicitely in my first post :) ).

Cédric Moonen Software developer
Charting control [v1.4]

[Rajesh R Subramanian]

Cedric Moonen wrote:

Yes I got that but for what reason exactly ?

May be just to explore and learn the other ways of loading a DLL?! I had to always load DLLs the LoadLibrary() way when I was working for my first employer. They had a bunch of third party DLLs to use in the project, and no corresponding .lib files. There might be a similar situation. Could be anything. But just keep the CPMRU handy, just in case. :-D

Nobody can give you wiser advice than yourself. - Cicero .·´¯`·->Rajesh<-·´¯`·. Codeproject.com: Visual C++ MVP

[Rajkumar R]

Force Code wrote:

typedef DWORD (*GETNGLYPHS)(HDC hdc,LPCTSTR lpstr,int c,LPWORD pgi,DWORD fl);

generic Text data type and linking to ANSI version API.

Force Code wrote:

(GETNGLYPHS)GetProcAddress(LoadLibrary("gdi32.dll"), "GetGlyphIndicesA");

can cause problem if unicode build.