[cffi-devel] foreign-symbol-pointer weirdness

[Martin Simmons]

>>>>> On Tue, 11 Apr 2006 02:42:19 +0400, Samium Gromoff <_deepfire at mail.ru> said:
> Delivered-To: cffi-devel at common-lisp.net
> 
> On Tue, 2006-04-11 at 01:55 +0400, Samium Gromoff wrote:
> > here is the scenario:
> 
> [snip]
> 
> > (let ((foreign-ptr (foreign-symbol-pointer
> > "verse_send_connect_accept" :code)))
> >   (format t "foreign-ptr contents: ")
> >   (dotimes (i 16)
> >     (format t "~2,'0X " (the (unsigned-byte 8) (mem-ref
> > foreign-ptr :uint8 i))))
> >   (format t "~%"))
> > 
> > This code gives different printouts on CLISP/CMUCL/SBCL backends:
> > 
> > CLISP:
> > foreign-ptr contents: 55 89 E5 83 EC 28 8B 45 0C 89 44 24 04 8D 45 F8
> > CMUCL:
> > foreign-ptr contents: E9 26 AE C3 F9 90 00 00 00 00 00 00 00 00 00 00
> > SBCL:
> > foreign-ptr contents: E9 CE A2 A1 47 90 00 00 00 00 00 00 00 00 00 00
> > 
> > This amounts to foreign-symbol-pointer finding different things
> > on different lisps, in the same shared library.
> 
> Luis Olivera suggested using (foreign-symbol-pointer ... :data) instead
> of (foreign-symbol-pointer ... :code), and it worked just fine, now
> providing pointers to exactly same code!
> 
> Apparently in the CMU/SBCL case i`ve been fed pointers to proc linkage
> table entries or some lisp-specific trampolines.

Is there any problem with getting different code?  Using :data for code is not
portable.

__Martin