Solved

cyclical dll loading

Posted on 2001-07-26
3
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Last Modified: 2010-04-06
Hi
I have some DLLs like:
------------------------------------------------
library Report;
uses
  SysUtils,
  Classes,
  Main in 'Main.pas';
exports
  GetReportName name 'GetReportName';
end.

unit Main;
interface

uses Forms, Classes;
function GetReportName: String; export; stdcall;

implementation

const
  ReportName = 'Name1';

function GetReportName;
begin
  Result := ReportName;
end;

end.
------------------------------------------------


And EXE app. It looks through the given directory, finds all DLLs that have the structure described above (with the different constant "ReportName") and for instance prints the Name of the report in the DLL:

------------------------------------------------
type
  TGetReportName = function: String; stdcall;
var
  DllInstance: THandle;
  GetReportName: TGetReportName;
  ReportName: String;

. . . . .  

if ExtractFileExt(SearchRec.Name) = '.dll' then
begin
 DllInstance := LoadLibrary(PChar(SearchRec.Name));
 if DllInstance <> 0 then
 begin
  @GetReportName := GetProcAddress(DllInstance, 'GetReportName');
  if @GetReportName <> nil then
  begin
   ReportName := GetReportName;

   ShowMessage(ReportName);
  end;
  FreeLibrary(DllInstance);
 end;
end;

After finding the first DLL it's OK, but in the second iteration an exception is generated in the string:

ReportName := GetReportName;

ReportName variable unaccessible :(

What's wrong in my code?
0
Comment
Question by:vterekh
  • 2
3 Comments
 
LVL 20

Accepted Solution

by:
Madshi earned 50 total points
ID: 6322436
You have to add this line to your dll:

exports GetReportName;

You can delete the "export" calling convention. It has no effect in 32bit programming anymore.

Please add ShareMem at the first location of both your exe's and your dll's uses clause.

Regards, Madshi.
0
 
LVL 1

Author Comment

by:vterekh
ID: 6325700
2 Madshi:

Thanks a lot!
Adding ShareMem it started working.

But as for the string

exports GetReportName;

it was located in the

library Report;

Probably you didn't notice it.
0
 
LVL 20

Expert Comment

by:Madshi
ID: 6325805
Yep, missed that GetReportName...  :-)

About ShareMem: When using ShareMem you have to distribute Borland's memory manager dll with your application. It's named borlndmm.dll, if I remember right. You're allowed to do so...

Regards, Madshi.
0

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