[fpc-devel] Re: Exporting from Elf okay?

[Peter Vreman]

At 07:33 8-8-2005, you wrote:

>| > Okay, I researched the topic. Of course, yes, you can export functions 
>from an
>executable
>| > on linux. But freepascal doesn't seem to like it just yet.
>|
>| How do you intend to use the exported symbols of an stand-alone
>| executable?
>| As a shared library, or how else?
>
>A shared library can call functions from the executable that it is running 
>from. Two way
>communication is very important to me.
>
>| Perhaps Linux and Windows executable files are not too different. On
>
>They aren't really, is what I found, after reseaching them.
>
>| Windows the file format (MZ) is the same for DLLs and EXE files, the
>| main difference is the invocation through the WinMain or LibMain entry
>| points. On Linux the shared libraries may have a similar implementation,
>| so that the exported symbols can be used only with shared library
>| modules.
>
>Functions can be used in executables in linux by calling the 
>-export-dynamic or -E with
>the linker (LD), but it isn't working yet with freepascal. Works with GCC 
>(also
>called -rdynamic).
>
>In windows, you can either get the handle of the exe using getmodule, and then
>getprocaddress(exehandle, 'myproc')or you can just call statically
>  procedure myproc; external 'myprogram.exe'; (instead of mylibrary.dll ).
>
>I asked some GCC guys "can an elf executable export functions?" and they 
>sort of laughed
>at me. They do it all the time, and they wondered why I was asking such an 
>obvious
>question. But I honestly think a lot of people don't know you can do this.
>
>Without being able to export functions form an executable, I find it's 
>sort of like having
>a client without a server. Why have a client without a server? To me, it 
>is essential for
>the executable to export functions.. (this is where the true power can be 
>squeezed out of
>plug-in systems - Lazarus RB Edition relies on this and would never work 
>without
>it...unless I used sockets, interprocess communication, or something similar.)

If gcc can do it also fpc can be made to do it. But for me it has no 
priority to add support for this to fpc. Ofcourse patches are welcome.


Peter