[fpc-other] [fpc-devel] OS/2 and DLLs

[Tomas Hajny]

On Thu, December 18, 2014 23:09, Mark Morgan Lloyd wrote:

> Noting somebody's earlier comment about the lack of DLL support being
> due to a linker limitation, I think this is unfortunate since when OS/2
> came out the fact that the binary formats were well-documented and
> supported by at least two linkers (MS and TopSpeed) was a significant
> advantage.
>
> I presume that the early enthusiasm had largely dissipated by the time
> IBM started pushing it as a 32-bit OS, with a new binary format etc.

In fact, the documentation is still available and there are several
linkers available as well (although Watcom WLINK is probably the only one
actively supported and free one). Moreover, the object file format was not
really changed by IBM much as far as I know (it's basically the same Intel
OMF format which was already used for DOS, although obviously extended as
necessary). The executable format was changed indeed, but it was still
closer to format already used by 16-bit MS Windows and various DOS
extenders than the PE format used for Win32. Note that the IBM linker has
been shipped with every copy of OS/2, so this wasn't the real problem.

However, it's a different linker than what is supported in FPC and it
needs a different object and library format from the one supported by the
OS/2 port of the GNU assembler; among other reasons, I would attribute
this to the fact that the original porter wanted to target DOS and OS/2
using the same compiled binaries and he could probably do it easier if
keeping the format already supported by the GNU world by that time.

Also, it would have been easier if the OS/2 port was contributed back to
the original project and kept maintained over time, or if the original GNU
C/as/ld/gdb porter (who did tremendous job, BTW) was available for help
with backporting his changes to the current source tree. Anyway - we have
to live with what is available now.

Tomas