09004: mononcol: If run without a cart, it crashes at start

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09004	Crash/Freeze	Minor	Always	Dec 7, 2024, 14:08	Dec 25, 2024, 17:22

Tester	Robbbert	View Status	Public	Platform	MAME (Self-compiled)
Assigned To		Resolution	Invalid report	OS	Windows 10/11 (64-bit)
Status [?]	Closed			Driver	misc/monon_color.cpp
Version	0.272	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	09004: mononcol: If run without a cart, it crashes at start
Description	If you run this system without a cartridge, for example in the debugger, it will crash.
Steps To Reproduce	>mame mononcol -d In the debugger use the g command. It will crash, dump, and exit.
Additional Information	C:\MAME>mame mononcol -d music_mcu.bin ROM NEEDS REDUMP WARNING: the machine might not run correctly. ----------------------------------------------------- Exception at EIP=00007ff75777194e ((anonymous namespace)::monon_color_state::spidir_w(int)+0x000e): ACCESS VIOLATION While attempting to read memory at 0000000000000000 ----------------------------------------------------- RAX=000001e670b36e20 RBX=000001e6737058a0 RCX=0000000000000000 RDX=0000000000000000 RSI=000001e670bf37d0 RDI=0000000000000000 RBP=00007ff768016e80 RSP=0000003be3af94d8 R8=0000003be3af9518 R9=0000003be3af9514 R10=0000000000000001 R11=fffffffff666ea26 R12=000001e670bf32f0 R13=000001e670bf32dc R14=000001e670bf32e0 R15=0000003be3af9980 ----------------------------------------------------- Stack crawl: 0000003be3af94d0: 00007ff75777194e ((anonymous namespace)::monon_color_state::spidir_w(int)+0x000e) 0000003be3af9550: 00007ff759757f95 (devcb_write<int, 1u>::operator()(int)+0x0045) 0000003be3af95c0: 00007ff75baee5f8 (axc51base_cpu_device::execute_run()+0x00d8) 0000003be3af9640: 00007ff759882f53 (device_scheduler::timeslice()+0x0323) 0000003be3af97c0: 00007ff75987ffc5 (running_machine::run(bool)+0x01c5) 0000003be3afede0: 00007ff75c9d202c (mame_machine_manager::execute()+0x024c) 0000003be3aff1d0: 00007ff7606f03da (cli_frontend::start_execution(mame_machine_manager*, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > const&)+0x03ea) 0000003be3aff4e0: 00007ff7606f0a0a (cli_frontend::execute(std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&)+0x007a) 0000003be3aff540: 00007ff75c9ccdd7 (emulator_info::start_frontend(emu_options&, osd_interface&, std::vector<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&)+0x0027) 0000003be3aff910: 00007ff762385c51 (luaopen_lfs+0xc5e771) 0000003be3aff960: 00007ff755ae12ee (__tmainCRTStartup+0x016e) 0000003be3aff990: 00007ff755ae1406 (mainCRTStartup+0x0016) 0000003be3aff9c0: 00007ffb419c7374 (BaseThreadInitThunk+0x0014) 0000003be3affa40: 00007ffb4219cc91 (RtlUserThreadStart+0x0021)
Github Commit

Flags
Regression Version
Affected Sets / Systems	mononcol

Attached Files

No.22601 cuavas Administrator Dec 18, 2024, 09:31	This system requires a cartridge to be loaded: mononcol_cartslot_device &cartslot(MONONCOL_CARTSLOT(config, "cartslot", mononcol_plain_slot)); cartslot.set_must_be_loaded(true); Intentionally bypassing that is not supported.
No.22608 hap Developer Dec 18, 2024, 12:59	It is supported: mame videopac -debug mame videopac -bench 3
No.22610 cuavas Administrator Dec 18, 2024, 14:40	No, MAME is incorrectly failing to raise the fatal error when certain options are used. MAME does not support running systems with nothing mounted in media devices that are marked required.
No.22611 Haze Senior Tester Dec 18, 2024, 14:51	It should probably in this case be possible to debug the internal ROM rather than just crashing, as unlike some systems there is at least that even when no cart exists, but yeah, I didn't realise -debug bypassed the mandatory requirement entirely, that seems like an issue beyond this report as for some systems there will simply be no code at all in such cases.
No.22692 Robbbert Moderator Dec 25, 2024, 15:13	Fixed this in my build, only had to add guards if a cart was there or not. Easy job.
No.22693 Haze Senior Tester Dec 25, 2024, 17:22 edited on: Dec 25, 2024, 17:22	Keep in mind any memory access code in the driver is a performance critical path, because the high frequency CPU does a lot of fetches, so if you've added guards in the critical path it will heavily impact performance.