Crash at startup on macOS 27 (Apple Silicon): JIT code-zone allocation fails

[dweinstein]

GT crashes at startup on macOS 27 (Apple Silicon) — JIT code-zone allocation fails

Summary: On macOS 27.0 (Darwin 27, Apple Silicon), GlamorousToolkit segfaults during VM init while reserving the Cog code zone, before the image loads. Fully reproducible; the image is never reached.

Environment

• macOS 27.0 beta, build 26A5353q (Darwin 27.0.0), Apple M1 Max (arm64)
• GT v1.1.436 — also reproduces on v1.1.417 and v1.1.400
• VM: 5.0-Pharo 10.3.9-46-gea9a2ea, built May 29 2026, Apple LLVM 14.0.0 (clang-1400.0.29.202), Production Spur 64-bit

Crash

• EXC_BAD_ACCESS (SIGSEGV), KERN_INVALID_ADDRESS at 0x0, faulting thread is the PharoVM thread, pc = lr = 0 (jump through a null pointer).
• Backtrace (symbolicated):

  ???                       +0
  libPharoVMCore.dylib      allocateMemoryForImagewithHeader+548
  libPharoVMCore.dylib      readImageNamed+3840
  libPharoVMCore.dylib      vm_init+208
  GlamorousToolkit          vm_bindings::interpreter::PharoInterpreter::run+36
  GlamorousToolkit          std::sys::backtrace::__rust_begin_short_backtrace+76
  GlamorousToolkit          core::ops::function::FnOnce::call_once+196
  GlamorousToolkit          std::sys::thread::unix::Thread::new::thread_start+408
  libsystem_pthread.dylib   _pthread_start+136
  libsystem_pthread.dylib   thread_start+8

allocateMemoryForImagewithHeader is allocating the JIT code zone; the disassembly of that routine contains the error string "Could not allocate codeZone in the expected place (%p), got %p", which strongly suggests the code zone can no longer be reserved at the expected virtual address under macOS 27's address-space layout.

Reproduction: Launch GlamorousToolkit on macOS 27 (Apple Silicon). Crashes immediately, every time.

Things ruled out

• Not worker-thread specific — --worker no reproduces identically.
• Not image corruption — the image-header size is read correctly (matches file size minus header); the crash is at heap/code-zone reservation, not parsing.
• Not quarantine / App Translocation — reproduces from a non-translocated path.

Happy to provide the full .ips privately if useful.