Re: [Sbcl-devel] Porting SBCL to Windows

[William H. N. <wil...@ai...>]

On Thu, Feb 22, 2001 at 01:23:19PM +0100, Rudolf Schlatte wrote:
> I have sketched some code, but nothing compilable yet.  In march, I
> will have some more time to work on it.  Could this C runtime, as soon
> as it's written, read a SBCL core file generated on Linux, assuming
> the correct lisp.h was linked in?

It depends on what you mean. If you mean could you take the 
core file you're running now and use it on Windows, the answer
is almost certainly "no":
  1. SBCL needs to know the sbcl.nm link map at GENESIS time, because
     it implements calls to runtime functions by jumping to the 
     address read from the nm file at this time. In order to make 
     the core work, you'd need to arrange for every C address which
     the core references directly to be in the exact same location
     in Windows as it was at GENESIS time on Linux. This would be
     much, much more trouble than it's worth.
  2. SBCL also needs to know the overall memory map at build time,
     because things like the location of NIL and the boundaries of the
     GCable spaces get hardwired into the code. It is unlikely
     that the memory map on Windows can be made identical to the
     memory map on Linux.
  3. Various things, e.g. (SIN X), get inlined into native calls into
     the C library. You'd need the exact same functions, with the exact
     same calling convention.
  4. Several OS-interface files, especially unix.lisp, work by
     hand-copying constants and structure layouts from system header
     files. It is unlikely that these are the same on Windows.

If you want to use Linux to generate a core file specifically for
Windows, it's less hopeless, though still unlikely. Problem #1
disappears if you take the nm file generated by Windows for the new
Windows runtime, copy it to Linux, use it as input for GENESIS, and
copy the resulting core file back to Windows. Problem #2 disappears if
you tell GENESIS about the Windows memory map. With problems #1 and #2
gone, there's some small chance that the core file might work, at
least a little bit. But I expect you'd still need to do some work, and
probably a significant amount of work, to address problems #3 and #4.

-- 
William Harold Newman <wil...@ai...>
software consultant
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