libSDL.dll.a is a MingW- or Cygwin-compiled link library. That's not
going to work on Windows with DMD and may very likely be the source of
your problem. If you want to link with a DLL link lib, then you need to
get the tool coff2omf[1] (part of the Extended Utilities Package[2]) run
it on SDL.lib (I suppose it might work on SDL.dll.a), and link with the
resulting converted file. Either that or compile SDL with DMC.
Alternatively, you could modify your binding to load SDL dynamically
like Derelict does. Then you don't need to fool around with any link
libs. But, you do need a fair amount of implementation code to load the
function symbols from the DLL.
[1] http://www.digitalmars.com/ctg/coff2omf.html
[2] http://www.digitalmars.com/download/freecompiler.html
The tool sounds cool but it seems that I have to buy it, so that's no
option for me. So I tried to compile SDL myself. I have to say I'm to
stupid for it. I tried to do the same thing as the makefile in
powershell. After I hacked together some solution that worked dmc
complained about missing Gl.h. It isn't there. So I added some MinGW to
the include-path and then I get a bunch of errors in SDL without
linenumbers. And anyways I am trying to compile it without MinGW, aren't
I. Please, help me!