Debug Delphi 3 experts with Delphi 3
Delphi 3 has a new feature "debug DLLs". It can be used to debug experts with the internal debugger. Just follow these simple steps, and debugging an expert can be fun:
Make sure that the expert is not installed. If there is this entry
rename this entry to "expert.xxx". (don't delete it, you'll need it later).
Otherwise, you cannot compile a new version.
Run Delphi, open your expert's project as used, compile it and set the break points you think you need.
Go to the menu item run | parameters. This is the new Delphi 3 feature mentioned above.
Surprise: the host application is Delphi itself! So, next to the field "host app", enter something like e:\Programs\delphi3\bin\delphi32.exe (with path)
Second trick: now we install the expert... If you have "expert.xxx" installed, rename that to "expert.dll". This will be used by any Delphi instance started from now on.
Run "your application" (= Delphi 3) using menu item run | run.
If you have enough RAM, Delphi is loaded and this instance will have your expert installed.
Activate the expert, you'll have the possibility to use the comfort of the first instance's internal debugger.
Close the right instance of Delphi - and you can modify/ recompile etc. your expert.
Взято с сайта https://www.delphifaq.com