Re: nullptr vs 0

From: Peter Dimov (pdimov_at_[hidden])
Date: 2022-05-23 20:06:53

Ion Gaztañaga wrote:
> On 22/05/2022 2:59, Peter Dimov via Boost wrote:
> > Compilers apparently are warning on the use of 0 as a null pointer
> > constant, suggesting we use nullptr instead. But compilers don't know
> > that we support C++03 where nullptr isn't a thing.
> >
> > Case in point: https://github.com/boostorg/throw_exception/pull/22
> >
> > ifdef-ing every use of nullptr is unwieldy, so maybe we need
> > BOOST_NULLPTR added to Boost.Config? That would expand to nullptr
> when
> > it's supported, and 0 otherwise.
> 
> Maybe we need the boost::nullptr_t type, emulated in C++ mode and "typedef
> decltype(nullptr) nullptr_t;" in compilers that support it...
> 
> And if nullptr/nullptr_t is provided by Boost.Config, without any heavy-include
> need, that would be perfect ;-)

That's not what Boost.Config is for.

Plus, since nullptr is a keyword, available without qualification in any scope, it
wouldn't be possible for us to provide a compatible replacement as we aren't
allowed to define things in the global namespace.

For our purposes it will probably work most of the time if defined in boost::
but there's no good way to define a global in a header under C++03 anyway.