[fpc-devel] OS/2 and DLLs
XHajT03 at hajny.biz
Wed Dec 17 21:30:09 CET 2014
On 17 Dec 14, at 19:27, Dave Parsons wrote:
> I needed to create an OS/2 DLL today & was disappointed by the compiler (v2.6.4) telling me that they were not supported.
> http://www.freepascal.org/faq.var#os2-dll section 6.3 seems to agree but is rather old.
> Can anyone confirm that this is still true?
Yes, it's still the case.
> Google didn't find much and it is not mentioned on the Future Plans page.
> What is the reason?
> Too difficult, no demand/request, no time or whatever.
The primary reason is the fact that creation of DLLs is not supported
by the ancient EMX port of the GNU linker ld.exe. As far as I know,
OS/2 ports of GCC (both the original EMX port and the recent ones)
solve this issue by using the IBM linker (possibly masked by EMXOMFLD
binary). However, this has several caveats (no special order):
1) Object files need to be translated/transformed from the a.out
format supported by the GNU binutils (as.exe and ld.exe) to Intel OMF
expected by the IBM linker (e.g. using the tool EMXOMF supplied with
EMX), or they need to be assembled using a different assembler
supporting this format (such as Watcom assembler or NASM) from the
very beginning, or support for direct creation of object files in
this format needs to be added to FPC directly. When I tried
translating object files created by FPC (using as.exe) with EMXOMF
some time ago, it failed to process some of them. I didn't manage to
find out the reasons so that I could possibly fix them at that point
in time (no we get to amount of time available mentioned by you).
2) Binaries linked with IBM LINK.EXE cannot be debugged using
GDB/PMGDB any longer (and no other debugger either, in fact, because
LINK.EXE would not support the stabs debug format which is currently
the only alternative supported for the OS/2 target in FPC).
3) There are certain special features which would need to be solved
differently if using a different linker (e.g. support for direct port
access). These wouldn't prevent most common uses, but they would
require spending some time on their resolution too.
Now back to your questions:
1) Is it possible to solve it? Yes, certainly.
2) Does the resolution require considerable amount of time? Yes, it
probably does (especially if the only person working on it is me).
3) Has there been strong demand? Well, not really (although some
questions already arose in the past).
I don't have much time for working on this task, but I'm willing to
spend some time on it as soon as I finish my current work on finally
properly supporting all UnicodeString Manager functions for OS/2
(that requires some time, but it is quite simple from technical point
of view). My motivation to work on the linker issue would be higher
if someone else joins me in this effort. Feel free to contact me
directly if you're interested.
More information about the fpc-devel