On macOS, `qemu -daemonize` fails with error "+[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called." ## Host environment - Operating system: macOS - OS/kernel version: macOS 14.6.1, Darwin Kernel 23.6.0 - Architecture: arm64 ("Apple Silicon"), Apple M3 chip - QEMU flavor: qemu-system-riscv64, qemu-system-ppc64, qemu-system-s390x - QEMU version: 9.0.2 (latest version, as installed with HomeBrew) - QEMU command line: ppc64 example here, see below for the three different flavors ``` qemu-system-ppc64 -smp 8 -m 8192 -daemonize -drive file=disk.qcow2,format=qcow2 -nic user,hostfwd=tcp::2299-:22 ``` ## Emulated/Virtualized environment - Operating system: Ubuntu (riscv64, s390x), Debian (ppc64) - OS/kernel version: Ubuntu 24.04, Debian sid - Architecture: riscv64, s390x, ppc64 ## Description of problem Context: I build [an open source project](https://tsduck.io/) on several operating systems and architectures. For riscv64, s390x, ppc64, I build in emulated virtual machines. The three emulated OS work correctly when running qemu manually and the project is correctly built. Now, I want to automate the process in a script: for each target architecture, boot the VM (start qemu as a background process), connect to the VM using ssh, build the software, collect the binaries, shut down the VM. Starting the same qemu command as used interactively as a background process with `&` does not work and fails immediately, apparently because of the lack of stdin. So, I added option `-daemonize` (and removed `-nographic` because an error message says the two options are incompatible). Using `-daemonize` instead of `-nographic`, all qemu command immediately fail with the following error: ``` objc[1141]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. objc[1141]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. ``` ## Steps to reproduce ``` $ qemu-system-riscv64 -machine virt -smp 8 -m 8192 -daemonize \ -bios fw_jump.bin -kernel u-boot.bin \ -device virtio-net-device,netdev=net \ -netdev user,id=net,hostfwd=tcp::2233-:22 \ -drive file=disk.qcow2,format=qcow2,if=virtio -device virtio-rng-pci objc[1141]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. objc[1141]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. $ qemu-system-s390x -machine s390-ccw-virtio -cpu max,zpci=on -smp 8 -m 8192 -daemonize \ -drive file=disk.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none \ -device virtio-blk-ccw,devno=fe.0.0002,drive=drive-virtio-disk0,bootindex=1 \ -nic user,hostfwd=tcp::2288-:22 objc[1209]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. objc[1209]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. $ qemu-system-ppc64 -smp 8 -m 8192 -daemonize \ -drive file=disk.qcow2,format=qcow2 -nic user,hostfwd=tcp::2299-:22 qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-cfpc=workaround qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-sbbc=workaround qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-ibs=workaround qemu-system-ppc64: warning: TCG doesn't support requested feature, cap-ccf-assist=on objc[1166]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. objc[1166]: +[__NSPlaceholderDate initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. ``` All the above commands work correctly when using `-nographic` instead of `-daemonize`. The virtual disks are the same as in the interactive runs, with a fully configured Linux OS (Ubuntu or Debian). ## Additional information From a [report from here](https://stackoverflow.com/questions/63041445/python-os-high-sierra-nsplaceholderdate-error), I tried to define the environment variable `OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES` before running qemu. The `[__NSPlaceholderDate initialize]` errors disappear but qemu still crashes immediately.