[Lazarus] Equivalent of a Windows DLL on RPi?

[Sven Barth]

Am 20.09.2015 07:03 schrieb "Bo Berglund" <bo.berglund at gmail.com>:
>
> I am investigating programming for the Raspberry Pi as described in my
> other thread. Could someone please outline if there is a concept like
> a Windows DLL also in Raspbian for the Pi?
>
> I have a DLL written in Delphi7 (or 2007), which implements a whole
> bunch of basic functions and I am wondering if a similar file as a DLL
> is used in Linux. If so could I port the existing DLL from Windows to
> freepascal and then to Linux on the Pi?
>
> I got some advice on the porting process in my other thread but in
> this case it involves the creation of a DLL equivalent so that the
> main programming could be done in for example Python while using the
> functions from the DLL code?

As the RPi uses a Linux (at least in normal cases) it also supports shared
libraries. They are written in FPC the same way as they are in Delphi (by
having a "library xyz" main file with an "exports" clause). This will
result in a ".so" file that you can load in FPC using the DynLibs unit with
LoadModule() and GetProcAddress() and in C-based languages using
dlopen()/dlsym() (don't know what Python uses, but I bet it's the same
across platforms ;) ).
Things to keep in mind though:
- declare exported functions as "cdecl"
- WideString is - unlike on Windows - not cross-library-safe
- and of course the usual points regarding strings, objects, etc. apply

Regards,
Sven
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