[Bug libstdc++/82039] New: -Wzero-as-null-pointer-constant triggers when calling std::allocate<...>::allocate

["max at maxbruckner dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82039

            Bug ID: 82039
           Summary: -Wzero-as-null-pointer-constant triggers when calling
                    std::allocate<...>::allocate
           Product: gcc
           Version: 7.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: max at maxbruckner dot de
  Target Milestone: ---

Created attachment 42087
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42087&action=edit
Code to reproduce the problem

gcc 7.1.1 emits a warning when enabling -Wzero-as-null-pointer-constant and
calling the allocate member function of std::allocator provided by libstdc++.

This only happens when calling allocate with only one parameter. So a
workaround is calling it with the second parameter set to nullptr.

I think this is due to the default parameter for the second parameter being a 0
instead of nullptr (not sure though, since I couldn't find the actual
implementation in the header files.