function EXE to DLL (Delphi) - delphi

Question

I am modulating my application to work with separate modules (plugin).
I have already successfully made my EXE application read and load the plugins, including the forms.
Now I need to do the inverse, export functions from the executable to DLL.
Example:
Inside my executable, it has a TMemo component. I want to create a function like this
function GetMemo(): widestring;
In my idea, whoever wrote the DLL plugin, when calling the function GetMemo(), would already take the contents of the TMemo in DLL.
It is possible?

Answer 1

The simplest way to handle this is to define a record of function pointers, and then have the EXE pass an instance of that record to each plugin while initializing it. The EXE can then implement the functions as needed and pass them to the plugins, without actually exporting them from its PE exports table like a DLL would.
For example:
type
PPluginExeFunctions = ^PluginExeFunctions;
PluginExeFunctions = record
GetMemo: function: WideString; stdcall;
...
end;
function MyGetMemoFunc: WideString; stdcall;
begin
Result := Form1.Memo1.Text;
end;
...
var
ExeFuncs: PluginExeFunctions;
hPlugin: THandle;
InitFunc: procedure(ExeFuncs: PPluginExeFunctions); stdcall;
begin
ExeFuncs.GetMemo := #MyGetMemoFunc;
...
hPlugin := LoadLibrary('plugin.dll');
#InitFunc := GetProcAddress(hPlugin, 'InitializePlugin');
InitFunc(#ExeFuncs);
...
end;
var
ExeFuncs: PluginExeFunctions;
procedure InitializePlugin(pExeFuncs: PPluginExeFunctions); stdcall;
begin
ExeFuncs := pExeFuncs^;
end;
procedure DoSomething;
var
S: WideString;
begin
S := ExeFuncs.GetMemo();
...
end;

Answer 2

unit uDoingExport;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TForm1 = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
procedure testproc; stdcall;
implementation
{$R *.dfm}
procedure testproc;
begin
ShowMessage('testproc');
End;
exports
testproc;
end.
I simply added the method I want to publish from within my EXE in the unit's Interface, and on the Implementation I added exports (method name). I am using stdcall not cdecl.
In my child, I can loadlibrary the exe file... or you can go a little crazy like Apache does, and in the previous code, add a loadlibrary, which loads a DLL, which intern can loadlibrary the caller.
My point was to show, your EXE is simply like a DLL (just a different binary header) and vise versa. Just slap EXPORTS. Proof it works, I ran tdump against the EXE:
Exports from ProjDoingExport.exe
1 exported name(s), 1 export addresse(s). Ordinal base is 1.
Sorted by Name:
RVA Ord. Hint Name
-------- ---- ---- ----
0005294C 1 0000 testproc
I know, a late answer, but, a great question!