pointer representation (was: Re: effect of free())
Rob McMahon
cudcv at warwick.ac.uk
Fri Sep 15 07:55:08 AEST 1989
In article <29250 at news.Think.COM> barmar at think.COM (Barry Margolin) writes:
>>Yes, it would. But the compiler writer would have been _seduced_ into that
>>mistake by the standard. People are encouraged to think of == as testing
>>for EQUALITY. In dpANS C, it appears that == does *NOT* have the properties
>>of equality, and at the very least this needs to be said clearly and
>>explicitly in the Rationale.
>
>This is only true if there can actually be non-interchangeable
>representations for pointers to the same location. I'd expect the compiler
>implementor for a system to know whether this is true, and implement the
>optimizer accordingly.
Who remembers the Burroughs B6700, which had (in Algol)
POINTER A, B;
IF A = B THEN ...
vs
IF A IS B THEN ...
compiling to
A
B
EQUL (sp?)
vs.
A
B
SAME
Sigh. Those were the days ...
Rob
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Rob McMahon, Computing Services, Warwick University, Coventry CV4 7AL, England
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