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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/112307] Segmentation fault with -O1
 -fcode-hoisting
Date: Tue, 05 Mar 2024 15:05:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112307

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
  return EnumeratorRange(Enumerator(std::views::single(Intersection())));

This creates a temporary Intersection object, then copies that into a
single_view object. Then that is copied into an Enumerator object which loo=
ks
like:

Enumerator {
  single_view<Intersection> range_;
  optional<single_view<Intersection>::_Iterator> begin_;
};

The range_ member is the copy of std::views::single(Intersection()) and the
begin_ member is initially empty.

Then that Enumerator is copied into an EnumeratorRange which calls Next() on
the new copy, which sets its begin_ member to point to the range_ member. T=
hen
the EnumeratorRange is returned.

So I think it's expected that the Enumerator points to itself, because of t=
he
call to its Next() member.

BUT, the self-referential pointer is set to the address of the range_ member
before the return value is copied, and so goes out of scope when that objec=
t is
copied via registers and then copied again into the automatic variable in
main().

So yes, I think it's invalid for the same reason as PR 109945 comment 25
explains, and indeed giving any of the objects a non-trivial destructor
prevents it being copied via registers and so the pointer isn't invalidated=
.=