Is this an useful optimization ??

Posted Apr 21, 2008 6:50 UTC (Mon) by nix (subscriber, #2304)
In reply to: Is this an useful optimization ?? by mikov
Parent article: GCC and pointer overflows

Ah, right. Well, QoI is in the eye of the beholder: I happen to think that 
the semantics of pointer overflow are semantics that only a maniac would 
rely upon intentionally, so the *most* we need is an extension of the 
existing compiler warning that `comparison is always true' or something 
along those lines.

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Is this an useful optimization ??

Posted Apr 21, 2008 17:32 UTC (Mon) by mikov (guest, #33179) [Link]

I was thinking mostly of integers, not pointers. However I am hard pressed to think of an
example where a pointer overflow would not safely wrap around _in practice_. Even with x86 FAR
pointers, the offset will safely wrap around. There will be no trap and the comparison will
still work.

Are there many architectures, in use today, where pointers are not integers and do not wrap
around on overflow ? Secondly, do these architecture run Linux and are they supported by GCC ?

Regardless of the answer to these questions, why would people writing  code with zero chance
for running on those architectures, be maniacs ?

The C Standard is not a measurement for good programming. It simply has a set of restrictions
to ensure portability between all kinds of weird architectures (I should say it fails in this
miserably, but that is beside the point). However portability is not the only, and by far not
the most important measurement of code.