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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/106434] [12/13 Regression] Spurious -Wnull-dereference when
 using std::unique_copy() since r12-5187-g1ae8edf5f73ca5c3
Date: Wed, 30 Nov 2022 14:00:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106434

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
We diagnose

MEM[(struct _Alloc_hider *)0B]._M_p =3D 16B;

that's conditional on if (_178 =3D=3D 0B) so probably constant propagated f=
rom
that.  That on the other hand is conditional on if (_178 !=3D _179) with

_178 =3D unique.D.69649._M_impl.D.68955._M_finish;
_179 =3D unique.D.69649._M_impl.D.68955._M_end_of_storage;

from vector::insert:

    insert(iterator __position, const value_type& __x)
#endif
    {=20
      const size_type __n =3D __position - begin();
      if (this->_M_impl._M_finish !=3D this->_M_impl._M_end_of_storage)
        if (__position =3D=3D end())
          {=20
            _GLIBCXX_ASAN_ANNOTATE_GROW(1);
            _Alloc_traits::construct(this->_M_impl, this->_M_impl._M_finish,
                                     __x);
            ++this->_M_impl._M_finish;
            _GLIBCXX_ASAN_ANNOTATE_GREW(1);

for some reason __position is NULL here, from iin.iter._M_current =3D 0B; it
seems.

I'm a bit lost here.=