🚀 go-pugleaf

In article <1992Dec17.164818.2198@craycos.com> jrbd@craycos.com (James Davies) writes:
 >Character variables are passed by descriptor.  The descriptor contains
 >the address of the first word, the starting offset in that word,
 >and the length of the variable in bytes, all packed into a 64-bit word.
 >The format of the descriptors varies by model, but the Cray-2 and 3 have 
 >the starting bit offset in the upper 6 bits of the word, the length in the
 >next 26 bits, and the word address in the lower 32 bits.  C character pointers
 >have the same format, except that the length field isn't used.
 > 
Right.  Which makes me wonder.  Could you publish a list of standard Unix
programs that were broken and revealed such by this particular character
pointer implementation?  (Like /bin/sh which is really awful.)  It ought
to be more common knowledge that:
1.  type1 pointers have not necessarily the same format as type2 pointers,
and:
2.  the low order bit(s) of a word aligned pointer can not be freely used as
    a marker.
(On the other hand, one of the Cray C compilers had a bug where in some
cases the upper bits of a char pointer were cleared when it was passed as
a parameter, so apparently Cray did not know this all at that time
either :-).)
-- 
dik t. winter, cwi, kruislaan 413, 1098 sj  amsterdam, nederland
home: bovenover 215, 1025 jn  amsterdam, nederland; e-mail: dik@cwi.nl