lisa@ncrcae.UUCP (Lisa McAlhany) (06/25/85)
I am currently porting GNU Emacs to the NCR Tower XP, which runs UNIX System V. Has anyone ported GNU Emacs to a System V machine yet? I have encountered some difficulty, mostly due to differences in System V and 4.2 BSD system calls. However, my latest problem concerns the bit-fields used in the Lisp_Object. Neither the Tower (and Motorola PCC2 compiler) nor our SUN will allow signed integers in a bit field (the s.val part of a Lisp_Object). Has anyone else ported GNU emacs to a System V machine? If so, I would appreciate any comments on how you solved these problems. Lisa Campbell ncrcae!lisa
guy@sun.uucp (Guy Harris) (07/02/85)
> However, my latest problem concerns the bit-fields used in > the Lisp_Object. Neither the Tower (and Motorola PCC2 compiler) > nor our SUN will allow signed integers in a bit field (the s.val part > of a Lisp_Object). Any C program that assumes that bit fields can be signed integers is broken; K&R makes no such commitment - in fact, it explicitly mentions that the PDP-11 implementation makes all bit fields unsigned. Signed bit fields are a nuisance to implement on machines without bit-field instructions; you can extract a zero-extended field with a shift and an AND but you have to do a bit more work to sign-extend a field. Sounds like the GNU emacs code has fallen victim to the "the whole world looks like a VAX" syndrome. If anybody fixes this, it should be sent back to RMS to avoid further annoyance. Guy Harris