RE: [Caml-list] flexdll circular dependency on ocamlc: Impossible to built ocaml for mingw without using some prebuilt binaries?

[David Allsopp <dra-news@metastack.com>]

Alain Frisch wrote:
> On 24/10/2015 14:51, David Allsopp wrote:
> > Alain Frisch wrote:
> >> On 24/10/2015 11:50, Soegtrop, Michael wrote:
> >>> Also I wonder why flexdll/flexlink is required. The documentation of
> >>> flexdll states:
> >>>
> >>> Windows DLL cannot refer to symbols defined in the main application
> >>> or in previously loaded DLLs.
> >>>
> >>> In my experience this is not true. At least when using MSVC one can
> >>> declare functions in the main executable as DLL-export. Then when
> >>> linking the main executable an import library is created in the same
> >>> way as when building a DLL by the linker. The DLL can then link to
> >>> this import library and can access the functions  in the main
> >> executable.
> >>
> >> Dynlink follows a different model: dynlinked units are not tied to a
> >> specific main executable.  A myplugin.cmxs can be dynamically linked
> >> by any application that provides the required interfaces.
> >
> > Wouldn't that still be true with the .def/.a approach, though?
> 
> I don't see how this would work without changing the compilation model.
> Would you generate an import library for each .cmi file?

Yes - but I wasn't taking the compilation model as fixed. I was (purely hypothetically, obviously!) imagining that flexlink (or some such) linker was still there and that it would generate the appropriate .def/.a files to allow the dll to be compiled, as it would also have access to the required .cmi files. That's quite similar to what flexlink already does, isn't it - just generating an import library to trick the actual/underlying linker rather than building separate tables embedded into .o/.obj files which get linked as well. 

But... 

> Also keep in mind that currently, dynlinked code can access directly data
> symbols from the main program (not just function calls that can more
> easily go through an import library).

... that sounds like the real "elevator explanation" for why things are as they are!


David