This package currently fails to build (at least on the amd64
architecture) with link time optimizations enabled.  For a background
for LTO please see

https://wiki.debian.org/ToolChain/LTO

The goal is to enable this optimization by default in an upcoming
Debian release in dpkg-buildflags for 64bit architectures.  The goal
is to get this package to build with link time optimizations, or to
explicitly disable link time optimizations for this package build.

To reproduce the build failure, enable the lto optimization in
testing/unstable by adding "optimize=+lto" to DEB_BUILD_MAINT_OPTIONS
in the debian/rules file, or if this macro is unset, just set it:

export DEB_BUILD_MAINT_OPTIONS = optimize=+lto

Please try to fix the build with lto enabled, fixing the packaging or
forwarding the issue upstream. If the issue cannot be fixed,
explicitly disallow building the package with lto by adding to your
rules file:

export DEB_BUILD_MAINT_OPTIONS = optimize=-lto

or adding that string to your existing setting of DEB_BUILD_MAINT_OPTIONS.

The full build log can be found at:
http://qa-logs.debian.net/2022/06/09/dpkglto/herbstluftwm_0.9.4-5_unstable_dpkglto.log
The last lines of the build log are at the end of this report.

[...]
        elif method == 'longopt':
            autostart = tmpdir / 'somename'
            args += ['--autostart', str(autostart)]
        else:
            autostart = tmpdir / 'somename'
            args += ['-c', str(autostart)]

        autostart.ensure()
        autostart.write(textwrap.dedent("""
            #!/usr/bin/env bash
            echo "hlwm autostart test"
        """.lstrip('\n')))
        autostart.chmod(0o755)
        env = conftest.extend_env_with_whitelist(env)
        hlwm_proc = HlwmProcess('hlwm autostart test', env, args)

        # TODO: verify the path as soon as we have an autostart object

../tests/test_autostart.py:53:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <conftest.HlwmProcess object at 0x7f337747ea10>

    def shutdown(self):
        self.proc.terminate()

        # Make sure to read and echo all remaining output (esp. ASAN messages):
        self.read_and_echo_output(until_eof=True)
        self.proc.stdout.close()
        self.proc.stderr.close()

        if self.proc.returncode is None:
            # only wait the process if it hasn't been cleaned up
            # this also avoids the second exception if hlwm crashed
            try:
                assert self.proc.wait(PROCESS_SHUTDOWN_TIME) == 0
            except subprocess.TimeoutExpired:
                self.proc.kill()
                self.proc.wait(PROCESS_SHUTDOWN_TIME)
../tests/conftest.py:473: Exception
---------------------------- Captured stdout setup -----------------------------
Running: Xvfb -nolisten tcp -screen 0 800x600x24 -noreset +extension RENDER -displayfd 16
Xvfb is using the display ":1"
---------------------------- Captured stderr setup -----------------------------
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
The XKEYBOARD keymap compiler (xkbcomp) reports:
Errors from xkbcomp are not fatal to the X server
----------------------------- Captured stdout call -----------------------------
hlwm autostart test
----------------------------- Captured stderr call -----------------------------
EWMH: 0 desktops:
0 managed clients:
./src/xconnection.cpp: 227: compositing manager = 0
./src/main.cpp: 361: Interrupted by signal 15
=========================== short test summary info ============================
FAILED ../tests/test_autostart.py::test_autostart_path[xdg] - Exception: herb...
!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!
=================== 1 failed, 2 passed in 183.01s (0:03:03) ====================
make[1]: *** [debian/rules:17: override_dh_auto_test] Error 1
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
make: *** [debian/rules:7: build] Error 2
dpkg-buildpackage: error: debian/rules build subprocess returned exit status 2