[Larceny-users] Apparent bug in lib/Ffi/tramp.sch

[David Rush]

This is pretty straightforward. I had a program that was invoking a
Scheme callback from inside another FFI call and would give this
error:

Error: i386 callback: bad selector arg-single
Entering debugger; type "?" for help.
debug> b
=> compiled procedure debug/enter-debugger
compiled procedure ffi/make-callback
(c:\tools\larceny\larceny-0.97-bin-native-ia32-win32\/lib/Ffi/tramp.sch
: 133 : 1)
compiled procedure ffi/make-callback
(c:\tools\larceny\larceny-0.97-bin-native-ia32-win32\/lib/Ffi/tramp.sch
: 133 : 1)
compiled procedure #f
(c:\tools\larceny\larceny-0.97-bin-native-ia32-win32\/lib/Base/std-ffi.sch
: 339 : 15)
compiled procedure #f
(c:\tools\larceny\larceny-0.97-bin-native-ia32-win32\/lib/Base/std-ffi.sch
: 502 : 5)
compiled procedure #f
(c:\tools\larceny\larceny-0.97-bin-native-ia32-win32\/lib/Base/std-ffi.sch
: 502 : 5)
compiled procedure #f
... etc


and after poking around a bit around a bit I found that this code in
tramp.sch was in fact the culprit:

(define (ffi/make-callback abi proc arg-descriptor ret-descriptor)
...
(case (car args)
((signed32 unsigned32 pointer)
((abi 'arg-word) tr))
((signed64 unsigned64)
((abi 'arg-word2) tr))
((ieee32)
((abi 'arg-single) tr))
((ieee64)
((abi 'arg-double) tr))
(else ???)))
...

changing the arg-single and arg-double to arg-ieee32 and ard-ieee64
respectively seems to make everything work ok. Well ok, enough for me
to move on to the next crash :)

david