Robert Dewar wrote: > Richard Guenther wrote: > >> On Wed, 21 Dec 2005, Andrew Haley wrote: >> >> >> >>> Richard Guenther writes: >>> > > The problem in this PR is that code like in the testcase (from >>> > OpenOffice) assumes that pointer overflow is defined. As the >>> > standard does not talk about wrapping pointer semantics at all (at >>> > least I couldn't find anything about that), how should we treat >>> > this? >>> >>> Look at Section 6.5.6, Para 8. The code is undefined. >>> >> >> This talks about pointers that point to elements of an array object. >> It does not talk about doing arithmetic on arbitrary pointer >> (constants), >> which is what the code does. >> > Right, but that's the point. "doing arithmetic on arbitrary pointer" > values is > not defined, it is not even defined to compare two pointers pointing > to two > different objects. > While that is true according to the standard, I believe that on most systems you can compare any two pointers. In particular, the C++ standard does require a total ordering on pointers, and at the moment that is implemented for all systems by just doing "a < b" on the two pointers.
Chris
