[dragonegg PATCH] Fix debug info for std::nullptr_t

[Peter Collingbourne]

On Wed, Jun 26, 2013 at 02:42:49PM -0700, David Blaikie wrote:
> On Wed, Jun 26, 2013 at 2:35 PM, Peter Collingbourne <peter at pcc.me.uk> wrote:
> > So the name is left unspecified.  Unsurprisingly, Clang and GCC have
> > diverged here -- Clang uses "nullptr_t" as the name while GCC uses
> > "decltype(nullptr)".  A standards proposal of sorts [1] proposes that
> > "decltype(nullptr)" be used.
> > [1] http://wiki.dwarfstd.org/index.php?title=C%2B%2B0x:_Null_pointer
> 
> The proposal (which isn't proposing anything) merely states that "the
> type of nullptr is decltype(nullptr)" which is true but incomplete,
> the C++ standard states "The pointer literal is the keyword nullptr.
> It is a prvalue of type std::nullptr_t." (though I'll admit we
> probably don't put the nullptr_t type in the std namespace)

It's a badly written proposal.  The actual "proposal" (to use
"decltype(nullptr)" as the name) is hidden in the "example" section
(and could possibly be inferred from the other sections and a leap
of faith).

I wouldn't call the proposal incomplete, at least not in the way
you mention.  If anything, the standard contains similarly circular
definitions.  [support.types]p9 defines std::nullptr_t as a typedef
for decltype(nullptr), which is probably the closest the standard
gets to a "canonical" type for nullptr (which needn't be in the
std namespace, or any namespace at all really).  It looks like the
standard uses std::nullptr_t as a convenient shorthand throughout,
without needing to talk about the canonical type of nullptr.  So it
isn't clear why the canonical nullptr type should be in std.

Thanks,
-- 
Peter