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GetProcAddress

Posted on 2004-09-20
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Last Modified: 2010-04-04
I'm trying to dynamically load a DLL. I call LoadLibrary to get my handle, then I typically use GetProcAddress to assign the function to a variable. However, I need to be able to do it using the known index number instead.

Statically I do it like this: function Myfunction(MyData:Integer):Integer; stdcall external 'MyDLL.dll' index 76;

How can I do this dynamically?
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Question by:rbohac
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15 Comments
 
LVL 17

Expert Comment

by:mokule
ID: 12106239
var
  sr: TSearchRec;
  h: Longint;
  GetStatMenu: function: Pchar; stdcall;
  GetStatSubMenu: function: Pchar; stdcall;
begin
        h := LoadLibrary(PChar(sr.Name));
        if h <> 0 then
          begin
          GetStatMenu := GetProcAddress(h,PChar('GetStatMenu'));
          GetStatSubMenu := GetProcAddress(h,PChar('GetStatSubMenu'));
          if Assigned(GetStatMenu) and Assigned(GetStatSubMenu) then
            begin
// functions available
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Author Comment

by:rbohac
ID: 12106317
Right.. using the index number please. NOT the name
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LVL 6

Author Comment

by:rbohac
ID: 12106342
Nevermind. I figured it out. You can pass the index as an ordinal parameter:

GetProcAddress(hDLL, PChar(Integer(76)));
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LVL 17

Expert Comment

by:Wim ten Brink
ID: 12106550
I was about to give the correct answer but noticed the question has been answered here. :-)
However, this happens to be useful information so I suggest to refund, close and PAQ it instead. For completeness, I'll add more information from the MSDN site. Keep in mind that if you use an ordinal number, the high-word must be 0.

The GetProcAddress function retrieves the address of an exported function or variable from the specified dynamic-link library (DLL).
FARPROC GetProcAddress(HMODULE hModule, LPCSTR lpProcName);

Parameters
hModule [in] Handle to the DLL module that contains the function or variable. The LoadLibrary or GetModuleHandle function returns this handle.
lpProcName [in] Pointer to a null-terminated string that specifies the function or variable name, or the function's ordinal value. If this parameter is an ordinal value, it must be in the low-order word; the high-order word must be zero.

Return Values: If the function succeeds, the return value is the address of the exported function or variable. If the function fails, the return value is NULL. To get extended error information, call GetLastError.
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LVL 22

Expert Comment

by:Ferruccio Accalai
ID: 12109849
--> so I suggest to refund, close and PAQ it instead...
I agree with Workshop_Alex also due for his good additions

F68 ;-)
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LVL 22

Expert Comment

by:Ferruccio Accalai
ID: 12109855
Nevermind, misreaded the -> PAQ-ing the question and refunding points
:)
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LVL 20

Expert Comment

by:Madshi
ID: 12110353
Just a side note: Using GetProcAddress with index numbers doesn't work for kernel32 APIs in win9x. Microsoft did this to prevent system hackers from accessing undocumented APIs. Of course there are ways to work around that limitation...   :-)
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Expert Comment

by:Wim ten Brink
ID: 12110625
Win9x? Does that still exist? ;-)
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Expert Comment

by:Madshi
ID: 12111068
Oh yes. I still get even support requests about win95 now and then...   :-/
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LVL 22

Expert Comment

by:Ferruccio Accalai
ID: 12111105
Unfortunately it still exists :( I've about 30 customers using already Win95 and there's no way to convince them to upgrade their systems... :(((
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LVL 14

Expert Comment

by:DragonSlayer
ID: 12120825
Win95... urggh... well, at least I managed to persuade all my Win95 users to upgrade to at least IE4 to get some of the *not-so-new-anymore* new features...
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Accepted Solution

by:
Lunchy earned 0 total points
ID: 12148862
Closed, 50 points refunded.
Lunchy
Friendly Neighbourhood Community Support Admin
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LVL 17

Expert Comment

by:Wim ten Brink
ID: 12152455
@ee_ai_construct, it has been answered by the expert himself. We just added a few more comments to this question to complete the answer. My suggestion was to PAQ it and am glad it is PAQ'ed.
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