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An almost complete DLL guide!
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| Submitted on: |
9/3/2003 10:42:42 PM |
| By: |
D Davis
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| Level: |
Intermediate |
| User Rating: |
By 49 Users |
| Compatibility: |
C++ (general), Microsoft Visual C++ |
| Views: |
68964 |
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(About the author) |
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+ Creating ActiveX DLL's in VB (and compatability issues),
+ Creating DLL's in C++,
+ Using ActiveX DLL's in VB apps,
+ Using Non-ActiveX DLL's in VB app and C++ apps,
+ Loading DLL's DYNAMICALLY in both VB and C++ (Good for plug-ins),
+ Calling a function by a string (Good for scripting programs).
This article was written for alot of reasons. For one, I needed to learn how to load and use DLL's and get a better understanding of doing so. Another was because there are so many shxtty examples out there today it's not even funny. Plus I found ZERO information on most of the stuff I go over. Every tutorial I've seen on how to make a DLL covers making one, then using the 'Declare' statement to utilize them. Not any good for plug-ins. Plus, the other half of the tutorials didnt even work! Anyways, I wrote this to try and sum up all of the half-ass tutorials and the complex, cryptic information and fill in the non existant information. I try to explain as best as I can. I know there might be slight changes that have to be done in order for it to work with you, but so be it. Make them and write about it to teach others.
I hope that this gives everyone a better idea of how to use DLL's and add flexability to their applications/games.
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Other User Comments
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 9/3/2003 10:51:20 PM: D Davis
Yes, I did post this in two categories since it deals with VB and C++.
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9/4/2003 4:46:08 AM: Psyc
very good article.. thanks! :) [5 glbs]
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9/5/2003 2:14:42 PM: maniac
very nice, 5 from me
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9/7/2003 8:00:23 AM: Ali Akbar
Excellent Article. Thanks.
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9/7/2003 12:21:30 PM:
very nice, i was wanting to learn some of that stuff
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9/10/2003 4:38:01 AM:
Very useful article, with useful information.
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9/11/2003 5:27:36 AM: John Bell
Umm, stdafx? ack....I prefer the hard way. If you want info on loading dll's into other processes(cross-task subclassing) I submitted an article on how to do this for aol. fallenhobit is the name its submitted under. Peace.
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9/11/2003 10:13:38 AM: D Davis
I agree! I only used the stdafx for easy setup purposes. that's it. I prefer the hard way as well!
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9/12/2003 2:17:31 PM:
Thanks for the article! I've been wanting to do some of this myself and this will at least get me started before I head off into the dark...
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9/16/2003 4:08:12 PM: John Mikhaiel
just wanted to let you know that in the Accessing you Dll Code, before the end of the process, its better to include the following line:
Set MyDll = Nothing
to free it up this way itll free up memory wit it, and its unloaded properly. the reason y i think it should be included is cause you also included the loading process (CreateObject) so if the code loads it, it should unload it. not tryin 2 be smart or anythin.
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9/16/2003 4:20:36 PM: John Mikhaiel
also for users of older vb versions:
vb5 supports ActiveX Dlls, and the 32bit version of VB4 (but ActiveX Dlls were called OLE Dlls). the 16bit version of VB4 supports only ActiveX EXEs which if written correctly are the same as the Dlls but can also be stand-alone programs (NOTE That vb4 16bit is only good for compatibilty with windows 3.1 and is pretty useless otherwise, vb4 32, and 16 are on the same installation CD).
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10/9/2003 7:11:19 PM: Jonathan Ho
Just what I needed. Very concise. 5 from me!
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12/3/2003 4:47:30 PM: Wolf McCloud
I don't really see the use of this for me but it looks nice for beginners that can't learn by themselves... I'll vote like other people. :)
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12/3/2003 5:05:30 PM: D Davis
This article was meant for people who have never been involved in complex projects, or have no experience with design docs. Hopefully it didnt come off as a guideline for experts as well as it was not intended to be. It's basically a place to start for those who have never worked in organized projects.
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12/25/2003 6:51:49 AM: mugman21
PART 1:
Great Job, this is a very nice piece of work.
First, when calling the dll, there is no need for all the fancy api calls (load library, getprocaddress,freelibrary yada yada yada). Just do this... In your dll, change:
int MyDLLFunc1() {
MessageBox(NULL,"My DLL Function 1","",MB_OK);
return true;}
to:
int _stdcall MyDLLFunc1() {
MessageBox(NULL,"My DLL Function 1","",MB_OK);
return true;
}
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12/25/2003 6:52:20 AM: mugman21
PART 2:
NOTE THE KEY PRASE "_stdcall" I ADDED!!!
After that is done, you can call the dll normally, like anyother.
For example, in vb just do a "Private|Public declare function MyDLLFunc1 lib "The_DLL_Name" () as long" This goes for C++ as well. This makes it a lot easier. As you can see, in vb after you declare the api to call it you only use it's name:
Command_Click()
MyDLLFunc1
End Sub
One thing you mentioned in your article is the use of .def files. I use that method myself, but if I recall correctly, you said you did not know of any other way to export functions. This function __declspec(dllexport) allows you to do it without creating a .def file. I never use it, although it supposedly creates a smaller dll.Thanks for your submission, and hope you release an updated article soon, thanks and take care.
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12/25/2003 7:09:51 AM: mugman21
One more thing, the dll needs to be in the app.path directory, the winnt|windows dir, or the system32 dir. D Davis, I hope you would release an update to this article soon, I think what you created was excellent.
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1/19/2004 9:07:05 AM:
Listen to this dude he knows what hes talking about, ok
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1/27/2004 3:03:28 AM: RAJENDRA
Very helpful articles
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2/6/2004 6:11:47 AM: Abdul Rafay Mansoor
Thanks for the simple explaning style, but man i got this DEBUG ERROR when i run client exe it says "ESP not saved properly across the function call...as a result of calling a function declared with one calling convention with a function pointer declared with different calling convention" if i comment out the "HelloWorld" (C++)message box the it works fine.. any suggestions.??
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2/16/2004 4:43:40 PM:
Has anyone noticed that the 2nd function: MyDLLFunc2(char *TEXT) takes a string pointer as an argument, but that the section on how to access the functions from VB only gives an example using MyDLLFunc1 which does not have an argument. Anyone know how to pass a string argument to callwindowproc in visual basic so Tha MyDLLFunc2 will work?
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4/28/2004 4:18:56 AM:
The article is nice. I 've already implemented the code but I got this DEBUG ERROR when i run program it says "ESP not saved properly across the function call...as a result of calling a function declared with one calling convention with a function pointer declared with different calling convention"
Can you please help me?
Thanx
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5/20/2004 1:06:07 AM: Henry_Mendes
Very good article. I were looking for a tutorial that teaches how to use C++ DLLS in VB app and this does!!! Thanks a Lot! Sorry with my engish mistakes!
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6/12/2004 10:11:35 AM:
That Debug error is very annoying, I think I’ve solved it though. Instead of returning an 'int' return 'LONG WINAPI', e.g.
LONG WINAPI MyDLLFunc2(LPSTR Text)
{
MessageBox(GetFocus(),Text,
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6/22/2004 10:50:42 AM: Alexander Wuzinger
zu __declspec(dllexport):
'__declspec(dllexport)XXX' Exportiert eine Function zwar ohne ein .def Datei, diese hat dann jedoch einen namen wie '??0XXX@@AAE@PBQBD@Z'
zu: MyDLLFunc2(char *TEXT):
Dieses Problem ist mir auch aufgefallen, weis vieleicht irgendjemand, wie man parameter übergiebt ? vieleicht mit pointern ????
Bitte um antwort
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9/24/2004 3:40:30 AM: Sriniwas
Good Man. This is a nice article for fresher. Thanks for Great Work.
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3/23/2005 9:51:15 PM:
hi, can you make a DevC++ version of that DLL? I've tried everything, but when I try to find functions address (GetProcAddress), it returns 0 (zero).
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3/28/2007 3:50:52 AM: Manas Ranjan Sahu
Hi,
A very good effort indeed. Just a minor aberration. The C++ DLL that you have written is a plain API DLL and not an ActiveX DLL as the VB DLL. I feel it would have been better to include an ActiveX DLL example in C++ contrasting it with the VB DLL.
Anyways, it does not anyway undermine the efforts put in by you.
Good work.
Bye
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4/11/2007 4:18:16 PM: Sebastian
hi, can you make a DevC++ version of that DLL? I've tried everything, but when I try to find functions address (GetProcAddress), it returns 0 (zero).
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3/31/2008 1:55:50 AM: chamika deshan
Hi
As someone mentioned there debug error can eliminated by using LONG WINAPI instead of int in DLL File MyDLLFunc2 function.
But how do we do that in main C++ code instead of changing the dll?
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3/31/2008 7:08:03 AM: chamika deshan
I found the way to eliminate the debug error by changing the C++ exe project instead of changing C++ dll project.
Instead of CALLBACK use __cdecl in the function pointer.
It's like this
typedef UINT (__cdecl * LPFNDLLFUNC1)(VOID);
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10/24/2010 8:57:02 AM: Dave Carter
Dustin, Thanks Man, Dave :)
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