Re: [boost] Bug/Incompatibility: Visual C++ 2005 checkediteratorslead to major crashes

From: Alan Stokes (alan_at_[hidden])
Date: 2006-06-19 12:40:32

On 18/06/06, David Abrahams <dave_at_[hidden]> wrote:
> You may be right.  Frankly I've never looked at the code used by MS
> and was going based on hearsay and dimly remember past experience with
> STLPort.
>
> IIRC from STLPort there are some operations that have to walk the
> entire list of iterators into a container (hence a loop), but I'm not
> sure if that affects conformity.  std::list<T>::erase, perhaps?
> That's supposed to be O(1) and maybe that becomes O(N) where N is the
> number of iterators into the list.

The "checked iterators" just include a check to make sure you don't go
beyond the end of a container (or do various other bad things); I
don't think this breaches any of the complexity requirements.

The MS library in a debug build does include some code that is
non-conformant because of the performance requirements. For example,
the binary search family of algorithms first checks that the range is
properly ordered (so they're O(N) instead of O(log N)). But the
release builds don't have those checks and so don't breach the
requirements.

I believe your argument was that boost should disable checked
iterators by default (even though they are enabled by default by the
compiler) because they were non-conforming. If that isn't true then I
suggest staying with the compiler default. It would still of course be
useful to be able to easily build the boost libraries without checked
iterators.

- Alan