Am 09.01.2018 um 16:03 schrieb Andre Pany:
I am building a bridge between Delphi and D. At the moment the
executable is written in D and the Dll (Firemonkey UI) is written in
Delphi. But I think I want to enable also the other way around. The D
coding which is then located in the Dll should be able to call Delphi
methods located in the executable. The whole idea idea is that all logic
is written in D and you only use the Framework (ui) and libraries Delphi
provides.
I think this might be a valid use case for a Dll calling functionality
located in the exe.
Kind regards
Andre
First let me say that what you are describing is a very uncommon and
ill-advised use case. As such there is not going to be any nice to use
workflow to acieve what you are trying to do. Still this doesn't mean
that it won't be possible.
Why ill-advised? What you're describing is a cyclic dependency between
your main executable and your dll written in delphi. If you google for
"cyclic dependency dll" you will usually get the advice to break your
cylic dependency by splitting your code into more dlls. My personal
experience shows the same. Cyclic dependencies in dlls are usually not
worth the additional effort and hassle. Also you want to export things
from your executable, which is also very uncommon. What you should be
doing is having 2 dlls and one executable. You have one common library
written in D that is build into a dll. Then you have your delphi library
which uses the common.dll. Finally you have your main executable written
in D which uses both the common.dll and your delphi.dll. This should
make it possibly to break the cycle and get you an easy setup.
If you absolutley must do it the way you describe it, its still
possible. You will have to compile all modules that export something
from your executable with the "-c -shared" parameters. E.g.
dmd -m64 -c -shared moduleThatExports1.d moduleThatExports2.d -ofexports.obj
Now you link the resulting exports.obj file into your executable by
calling dmd again
dmd -m64 restOfModules.d exports.obj delphi.lib -ofmain.exe
Finally you have to get the handle to your main executable by calling
HMODULE handle;
GetModuleHandleExA(0, null, &handle);
in your delphi dll and then fetching the function pointer for each and
every function you want to call from delphi via:
GetProcAddress(handle, "mangeledFunctionSymbol")
Now finally you can call these functions pointers from delphi and they
will call into the D code within your executable.
Instead of all that hassle you could instead just have a function in
your delphi dll:
void recieveFunctionPointer(const(char)* name, void* ptr);
which you call for every function that you want to make available from D
to delphi. Your delphi code then stores away these pointers depending on
the name. That way you don't need to export anything from your
executable and can build it normally. Instead of having a function call
per function you could obviosuly also use a struct that is defined the
same way in D and delphi and contains all relevant functions pointers.
--
Kind Regards
Benjamin Thaut
