[Bug c++/69922] New: Bogus -Wnonnull-compare for: ... ? static_cast<T*>(this) : nullptr

["sbergman at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69922

            Bug ID: 69922
           Summary: Bogus -Wnonnull-compare for: ... ?
                    static_cast<T*>(this) : nullptr
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sbergman at redhat dot com
  Target Milestone: ---

With trunk@233631:

> $ cat test.cc
> struct S2 { virtual ~S2(); };
> struct S1 {
>     virtual ~S1();
>     S2 * f(bool);
> };
> struct S3: S1, S2 {};
> S2 * S1::f(bool b) { return b ? static_cast<S3 *>(this) : nullptr; }

> $ g++ -Werror -Wnonnull-compare -c test.cc
> test.cc: In member function âS2* S1::f(bool)â:
> test.cc:7:59: error: nonnull argument âthisâ compared to NULL [-Werror=nonnull-compare]
>  S2 * S1::f(bool b) { return b ? static_cast<S3 *>(this) : nullptr; }
>                                                            ^~~~~~~
> cc1plus: all warnings being treated as errors