yadifad crashes on start up

[Y:A:D::I::F:A]

Compiler optimization bug generates wrong assembly causing SEGFAULT.

# apt -y install yadifa

---
# systemctl start yadifa

# systemctl status yadifa
× yadifa.service - YADIFA Domain Name Server
     Loaded: loaded (/usr/lib/systemd/system/yadifa.service; enabled; preset: enabled)
     Active: failed (Result: core-dump) since Fri 2024-06-07 12:30:24 UTC; 9min ago
   Duration: 1.284s
       Docs: man:yadifad(8)
    Process: 240604 ExecStart=/usr/sbin/yadifad --nodaemon -c $YADIFA_CONF (code=dumped, signal=SEGV)
   Main PID: 240604 (code=dumped, signal=SEGV)
        CPU: 274ms

Jun 07 12:30:22 ubuntu-2404 systemd[1]: Started yadifa.service - YADIFA Domain Name Server.
Jun 07 12:30:24 ubuntu-2404 systemd[1]: yadifa.service: Main process exited, code=dumped, status=11/SEGV
Jun 07 12:30:24 ubuntu-2404 systemd[1]: yadifa.service: Failed with result 'core-dump'.

---
# /usr/sbin/yadifad
Segmentation fault (core dumped)

---
# apt-cache policy yadifa
yadifa:
  Installed: 2.6.5-1build2
  Candidate: 2.6.5-1build2
  Version table:
 *** 2.6.5-1build2 500
        500 http://be.archive.ubuntu.com/ubuntu noble/universe amd64 Packages
        100 /var/lib/dpkg/status

---
# lsb_release -rd
No LSB modules are available.
Description: Ubuntu 24.04 LTS
Release: 24.04

---
Suggested workaround by disabling lto in debian/rules (confirmed locally)

"DEB_BUILD_MAINT_OPTIONS = hardening=+all optimize=-lto"

This bug is specific for ubuntu 24.04 (gcc 13.2). It does not affect ubuntu 22.04 or Debian 12 (gcc 12.2).

[Y:A:D::I::F:A (yadifa)]

Root cause (credit Richard Biener) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115432

struct file_output_stream
{

    union
    {
        void *voidp;
        int fd;
    } data;

    const output_stream_vtbl* vtbl;
};

struct output_stream
{
    void* data;
    const output_stream_vtbl* vtbl;
};

those are two unrelated types. Doing

 ((file_output_stream *)p)->vtbl = x;
 ... = ((output_stream *)p)->vtbl;

is invoking undefined behavior (unless -fno-strict-aliasing).