[llvm] r243996 - Avoid passing nullptr to std::equal.

[Yaron Keren via llvm-commits]

Ok, back to std::equal replacement...


2015-08-18 1:27 GMT+03:00 Aaron Ballman <aaron at aaronballman.com>:

> On Mon, Aug 17, 2015 at 6:18 PM, Yaron Keren <yaron.keren at gmail.com>
> wrote:
> > +aaron, reid
> >
> > Here is a patch disabling the iterator null pointer checking in Visual
> C++
> > debug mode. This makes std::equal behave as expected instead of
> asserting on
> > std::equal(nullpt,r nullptr, nullptr), saving an extra check just for
> Visual
> > C++ debug mode here and there.
> >
> > It should not cause any practical problem debugging as if a null
> iterator is
> > actually dereferenced (as opposed to compared) the debugger will stop on
> > location.
> >
> > What do you think?
>
> Mildly terrified. :-) This also disables really useful debugging tools
> in other parts of the STL that have definitely found bugs for us in
> the past. A lot of <algorithm>, <istream>, <ostream>, <locale>,
> <memory>, <string>, and <utility> make use of _DEBUG_POINTER, which
> this patch would disable.
>
> I would *strongly* prefer to not disable that debugging functionality,
> especially since this runtime-level debugging has found bugs our own
> tests have not.
>
> ~Aaron
>
> >
> >
> > 2015-08-17 23:45 GMT+03:00 Duncan P. N. Exon Smith <dexonsmith at apple.com
> >:
> >>
> >>
> >> > On 2015-Aug-17, at 13:43, Yaron Keren <yaron.keren at gmail.com> wrote:
> >> >
> >> > I'm trying another approach. The non-null validation goes through a
> >> > macro defined to a function which possibly may be predefined to
> nothing.
> >> > This will disable all null checking on iterators in debug mode which
> is
> >> > relevant to additional functions beyond std::equal. In practice it
> should
> >> > not be a problem since if a null iterator is actually dereferenced
> (not only
> >> > compared) then the debugger stops with invalid access anyhow.
> >>
> >> Well, this would be ideal :).
> >
> >
>
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