[MLton] power pc "port"

[Filip Pizlo]

> OK.  It just seems to be a more challenging approach because you're
> trying to solve two problems at once: compiling for Darwin/PowerPC and
> compiling a huge program (MLton).  Plus you have to fight the fact
> that you're using a really slow compiler (MLton compiled by SML/NJ).
> It's easier to first get compiling for Darwin/PowerPC right, using a
> fast compiler (MLton compiled by MLton), and then tackle huge programs
> and self compilation.  But, you do have to learn the upgrade-basis
> stuff sometime :-).

I just wanted to update everyone on the status of the PowerPC port.  Right
now, I've got a MLton compiled MLton (compiled on Luke's Linux box) almost
linking on Mac OS X.  Mac OS X has a bizarre linker, so I am not
expecting this step to be particularly pleseant.  Anyway, here are the
current errors:

ld: warning multiple definitions of symbol _main
mlton.0.o definition of _main in section (__TEXT,__text)
../runtime/libgdtoa.dylib(single module) definition of _main
ld: warning multiple definitions of symbol _strtod
../runtime/libgdtoa.dylib(single module) definition of _strtod
/usr/lib/libSystem.dylib(gdtoa-strtod.So) definition of _strtod
ld: warning multiple definitions of symbol _strtof
../runtime/libgdtoa.dylib(single module) definition of _strtof
/usr/lib/libSystem.dylib(gdtoa-strtof.So) definition of _strtof
ld: Undefined symbols:
_IEEEReal_getRoundingMode
_IEEEReal_setRoundingMode
_spawnve
_spawnvp
_etext

The multiple defintion problems are because Mac OS X's libSystem
(equivalent of libc) uses the gdtoa library.  However, it doesn't export
the gdtoa symbol.  So we may just have to live with these warnings (there
is a switch somewhere to suppress them).

The IEEEReal_getRoundingMode and IEEEReal_setRoundingMode errors are
an oversight - I'll have to hack runtime/basis/IEEEReal.c to have a
PowerPC case.

The spawnve and spawnvp errors are a puzzle to me.  I don't see where in
the MLton code these functions are defined.  Is there a dependant library
that I'm not seeing?  (I can easily implement these functions, but I don't
want to do that if they're already out there somewhere.)

The etext error may turn out to be annoying.  The MLton GC uses the _start
and etext symbols to figure out where the text segment sits.  
Unfortunately, the Mac OS X linker doesn't offer an etext symbol.  It
does, however, offer functions that give similar information: get_etext(),
get_end(), and get_edata().  However, the manual page (see
http://developer.apple.com/documentation/Darwin/Reference/ManPages/html/end.3.html)
makes clear that you're not really supposed to rely on those.  Perhaps if
a MLton GC expert could tell me exactly how etext is used, I can hack the
GC to be more Mac OS X-friendly.

--
Filip Pizlo
http://bocks.psych.purdue.edu/
pizlo@purdue.edu