[Bug 1920602] Re: QEMU crash after a QuickBASIC program integer overflow

[Philippe Mathieu-Daudé]

FErr# IRQ raise since bf13bfab084 ("i386: implement IGNNE"):

  Change the handling of port F0h writes and FPU exceptions to implement IGNNE.
  
  The implementation mixes a bit what the chipset and processor do in real
  hardware, but the effect is the same as what happens with actual FERR#
  and IGNNE# pins: writing to port F0h asserts IGNNE# in addition to lowering
  FP_IRQ; while clearing the SE bit in the FPU status word deasserts IGNNE#.

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https://bugs.launchpad.net/bugs/1920602

Title:
  QEMU crash after a QuickBASIC program integer overflow

Status in QEMU:
  Confirmed

Bug description:
  A trivial program compiled with QuickBASIC 4.5 with integer overflow
  will crash QEMU when ran under MS-DOS 5.0 or FreeDOS 1.2:

  C:\KILLER>type killer.bas
  A% = VAL("99999"):PRINT A%

  C:\KILLER>killer.exe
  **
    ERROR:../qemu-5.2.0/accel/tcg/tcg-cpus.c:541:tcg_handle_interrupt: 
assertion failed: (qemu_mutex_iothread_locked())
  Aborted

  QEMU version v5.2, compiler for ARM, and started with command line:

  qemu-system-i386 -curses -cpu 486 -m 1 -drive dos.img

  The same test under Ubuntu QEMU and KVM/x86_64 (QEMU emulator version
  4.2.1 (Debian 1:4.2-3ubuntu6.14)) will just silently hang the QEMU. On
  DOSBOX, the machine does not die and program outputs the value -31073.

  The EXE to reproduce the issue is attached.

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