BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Re: How to use DLLs          BorlandTalk.com Forum Index -> C++ Builder (IDE) View previous topic :: View next topic   Author Message Paul Guest Posted: Mon Jan 30, 2006 9:12 am    Post subject: Re: How to use DLLs Thanks, will give it a go today. "Michel Leunen" <nospam (AT) noreply (DOT) please> wrote Quote: Paul wrote: Not sure if this is the right group to ask. http://users.deltacomm.com/edmulroy/howto10.htm Michel -- ---------------------------------------- Michel Leunen mailto: see my homepage. C++Builder, BCC5.5.1 Web site: http://www.leunen.com/ ---------------------------------------- Back to top Mark Jacobs Guest Posted: Mon Jan 30, 2006 12:52 pm    Post subject: Re: How to use DLLs Paul wrote: Quote: Not sure if this is the right group to ask. But is there an example somewhere on how to use a DLL in an application? Below is a test DLL. Just don't know how to link it in and use it in an application (needs to be used by BCB or VC++ apps). #include <vcl.h #include #pragma hdrstop extern "C" __declspec(dllexport) void Evaluate(LPSTR); #pragma argsused BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fwdreason, LPVOID lpvReserved) { return 1; } //--------------------------------------------------------------------------- void Evaluate(LPSTR lpName) { MessageBox(NULL,TEXT("Borland"), lpName, MB_OK); } You could statically link the DLL to your app, but I favour dynamic loading of the DLL after the app has started. This is how I do it (please note : Timer2 closes the form after a 300ms delay, and my special type LPFNDLLFUNC1 which defines the DLL's procedure parameters) :- typedef bool (CALLBACK* LPFNDLLFUNC1)(); typedef bool (CALLBACK* LPFNDLLFUNC2)(char *,char *,int); typedef bool (CALLBACK* LPFNDLLFUNC3)(mystruct *); HINSTANCE mydllhandl; LPFNDLLFUNC1 mjhkproc; LPFNDLLFUNC2 mjh2proc; LPFNDLLFUNC3 mjh3proc; //--------------------------------------------------------------------------- void __fastcall TForm1::FormPaint(TObject *Sender) { static bool clld=false; if (clld) return; clld=true; mydllhandl=LoadLibrary("myspecial.dll"); if (!mjmsghk) { ShowMessage("Could not load MYSPECIAL.DLL - "+mjgetlasterror()); Timer2->Enabled=true; return; } mjhkproc=(LPFNDLLFUNC1)GetProcAddress(mydllhandl,"dll_function1"); if (!mjhkproc) { ShowMessage("Error dll_function1 GetProcAddress - "+mjgetlasterror()); Timer2->Enabled=true; return; } mjh2proc=(LPFNDLLFUNC2)GetProcAddress(mydllhandl,"dll_function2"); if (!mjh2proc) { ShowMessage("Error dll_function2 GetProcAddress - "+mjgetlasterror()); Timer2->Enabled=true; return; } mjh3proc=(LPFNDLLFUNC3)GetProcAddress(mydllhandl,"dll_function3"); if (!mjh3proc) { ShowMessage("Error dll_function3 GetProcAddress - "+mjgetlasterror()); Timer2->Enabled=true; return; } } //--------------------------------------------------------------------------- AnsiString __fastcall TForm1::mjgetlasterror() { LPVOID lpMsgBuf; AnsiString sret; FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, NULL,GetLastError(), MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT), (LPTSTR)&lpMsgBuf,0,NULL); sret=AnsiString((char *)lpMsgBuf); LocalFree(lpMsgBuf); return sret; } //--------------------------------------------------------------------------- // Later on in your code somewhere ... if (!mjhkproc()) ShowMessage("Oh deary deary me!"); if (!mjh2proc("String Parameter 1","String Parameter 2",4078)) ShowMessage("Whoops!"); //... // And finally free the library (usually in the form's OnCloseQuery routine) with :- FreeLibrary(mydllhandl); -- Mark Jacobs http://www.dkcomputing.co.uk Back to top Mark Jacobs Guest Posted: Mon Jan 30, 2006 9:10 pm    Post subject: Re: How to use DLLs Mark Jacobs <markj (AT) critical (DOT) co.uk> wrote on Mon, 30 Jan 2006 12:52:29 +0000 :- Quote: if (!mjmsghk) Should read if (!mydllhandl) Mark Jacobs Back to top Paul Guest Posted: Mon Jan 30, 2006 10:50 pm    Post subject: Re: How to use DLLs Thanks. Will read it more in the morning. "Mark Jacobs" <markj (AT) critical (DOT) co.uk> wrote Quote: You could statically link the DLL to your app, but I favour dynamic loading of the DLL after the app has started. This is how I do it (please note : Timer2 closes the form after a 300ms delay, and my special type LPFNDLLFUNC1 which defines the DLL's procedure parameters) :- Back to top Paul Guest Posted: Thu Feb 02, 2006 10:19 pm    Post subject: Re: How to use DLLs I managed to get a basic DL working in BCB, and test it in a BCB application (BCB6). But my fellow engineers haven't been able to get it to work in VC++ (Visual Studio 6). I'm going to put the project zip in the borland.public.attachments under the same subject. Can someone tell me if there is anything wrong with the project, code, or options, as to why it doesn't work. Last error that popped up was apparently a problem with ESP being incorrect, and possilbe calling conventiones were wrong??? The purpose of the DLL is to wrap up some useful VCL components from BCB and use them in VC++. Paul. "Michel Leunen" <nospam (AT) noreply (DOT) please> wrote Quote: Paul wrote: Not sure if this is the right group to ask. http://users.deltacomm.com/edmulroy/howto10.htm Michel -- ---------------------------------------- Michel Leunen mailto: see my homepage. C++Builder, BCC5.5.1 Web site: http://www.leunen.com/ ---------------------------------------- Back to top Michel Leunen Guest Posted: Fri Feb 03, 2006 6:55 pm    Post subject: Re: How to use DLLs Paul wrote: [snip] I replied in the attachment group. -- ---------------------------------------- Michel Leunen mailto: see my homepage. 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