09241: lx_frozen, rizstals: chd diff conflict

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09241	Crash/Freeze	Minor	Always	11 days ago	4 days ago

Tester	Robbbert	View Status	Public	Platform	MAME (Self-compiled)
Assigned To		Resolution	Open	OS	Windows 11/10 (64-bit)
Status [?]	Confirmed			Driver
Version	0.279	Fixed in Version		Build	64-bit
		Fixed in Git Commit		Github Pull Request #

Summary	09241: lx_frozen, rizstals: chd diff conflict
Description	The DIFF path does not include a gamename folder, therefore it's possible for CHD name collisions to occur. Currently there's 2 sets of 2 games that use the same-named chd, but of course with loose software any number of collisions could conceivably occur. Of the 2 sets, only one of them makes a DIF file - lx_frozen and rizstals. If you run one of them you get a dif, now run the other and you get the confusing message: sdcard.chd DIFF CHD ERROR: Invalid parent Fatal error: Required files are missing, the machine cannot be run. The first line conveys no meaningful info, while the 2nd line is just wrong. Right now, those 2 games don't work, but that could change. I suggest that a gamename folder be automatically added, same as the nvram folder is now, so that no such problem can occur now or in the future.
Steps To Reproduce	See above
Additional Information	List of duplicated chd names with different SHA1: r00.chd : used in mtchxlgld and mtchxlti - fortunately no dif from these sdcard.chd : used in lx_frozen and rizstals - dif collision prevents both games being able to be started There's many more cases of different games using the same identical CHD, and I didn't test to find out if any DIF files produced are compatible.
Github Commit

Flags
Regression Version
Affected Sets / Systems	lx_frozen, rizstals

Attached Files

No.23600 cuavas Administrator 8 days ago	This has always been an issue. It doesn’t affect loose software, though – MAME shouldn’t make diff files for loose CHDs, it should just mount them write-only if they aren’t uncompressed. You have to consider interaction with software lists, though. You could change it to use <system>/<label>.dif for CHDs specified by systems. It would mean clones that share a CHD would get different diff files, whether they’re compatible or not. This may be considered a good or bad thing. For software, there’s the question of whether the system should be in the path. You could use <system>/<list>/item/<label>.dif or just <list>/<item>/<label>.dif if the system is included or excluded. The latter would be more convenient for things like Mac hard disks, as the same disk image can usually boot a variety of systems, and you can install software then run it on multiple machines. However Windows installations have always required a lot more messing around to move from one machine to another, so PC hard disk software lists would still require making uncompressed copies of the disk image to use them with multiple emulated systems. Newer Linux distros tend to be reasonably portable across platforms, but older Linux distros and more traditional UNIX systems tend to require more effort to move to a different system (e.g. recreating device files).

No.23600

cuavas

Administrator

8 days ago

This has always been an issue. It doesn’t affect loose software, though – MAME shouldn’t make diff files for loose CHDs, it should just mount them write-only if they aren’t uncompressed. You have to consider interaction with software lists, though.

You could change it to use <system>/<label>.dif for CHDs specified by systems. It would mean clones that share a CHD would get different diff files, whether they’re compatible or not. This may be considered a good or bad thing.

For software, there’s the question of whether the system should be in the path. You could use <system>/<list>/item/<label>.dif or just <list>/<item>/<label>.dif if the system is included or excluded.

The latter would be more convenient for things like Mac hard disks, as the same disk image can usually boot a variety of systems, and you can install software then run it on multiple machines.

However Windows installations have always required a lot more messing around to move from one machine to another, so PC hard disk software lists would still require making uncompressed copies of the disk image to use them with multiple emulated systems. Newer Linux distros tend to be reasonably portable across platforms, but older Linux distros and more traditional UNIX systems tend to require more effort to move to a different system (e.g. recreating device files).