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From: "simon.marchi at polymtl dot ca" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/31281] [gdb] intrusive_list.h:329: internal-error:
 push_back: Assertion elem_node->prev == INTRUSIVE_LIST_UNLINKED_VALUE failed.
Date: Thu, 25 Jan 2024 03:51:12 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D31281

Simon Marchi <simon.marchi at polymtl dot ca> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |simon.marchi at polymtl do=
t ca

--- Comment #12 from Simon Marchi <simon.marchi at polymtl dot ca> ---
I made what I think is a fairly minimal reproducer:
https://godbolt.org/z/rbevnhG1f

node_ptr_1 is the node field address computed using the pointer to member
machinery.  node_ptr_2 is also the node field address, but computed directl=
y by
taking its address.  We would expect them to be the same, but they're not w=
ith
gcc 14 / trunk.  They are with other compilers.

Does this look sufficient to file a gcc bug?

Here's the code in case godbolt is down.

---

#include <cassert>
#include <iostream>

struct intrusive_list_node {
  void *next;
};

struct dummy {
  void *base;
};

struct thread_info : public dummy, public intrusive_list_node {
  intrusive_list_node node;
};

template <intrusive_list_node thread_info::*MemberNode>
struct intrusive_member_node {
  static intrusive_list_node *as_node(thread_info *elem) {
    return &(elem->*MemberNode);
  }
};

int main() {
  for (int i =3D 0; i < 100000; ++i) {
    thread_info *tp =3D new thread_info;
    auto node_ptr_1 =3D intrusive_member_node<&thread_info::node>::as_node(=
tp);
    auto node_ptr_2 =3D &tp->node;
    std::cout << "With tp =3D=3D " << tp << ", does " << node_ptr_1
              << " =3D=3D " << node_ptr_2 << " -> " << (node_ptr_1 =3D=3D n=
ode_ptr_2)
              << std::endl;
    assert(node_ptr_1 =3D=3D node_ptr_2);
  }
}

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