Hi Wolf, > Am 28.05.2025 um 22:32 schrieb Wolf Bergenheim <wolf+...@bergenheim.net>: > > Are you running in a VM or physical machine? What dos DR-DOS return?
It is running on an emulated Pentium system via 86box, on FreeDOS, MS-DOS and SvarDOS (EDR-DOS kernel). > Soo now I wonder what is the full value of register AX? I'd expect the kernel > to set values to indicate a drive not ready error. So for some reason bit 7 > of AH is set? So now I wonder why not? The test program may be downloaded from https://nextcloud.iww.rwth-aachen.de/index.php/s/2zzo8LrxKsA35bD For laziness I wrote it in Turbo Pascal. In the following there is the critical error sequence of the different kernels. The test program basically tries to open a file on a non-existing diskette, and then tries to write some bytes into it. The program aborts as soon as a DOS function returns an error. On the critical error return = 0 (IGNORE), FreeDOS returns a file handle. It returns 5 bytes written despite it did not write anything. Therefore previously EDIT did not detect an error. The system eventually hangs. MS-DOS and EDR-DOS kernels report errors via the INT21 calls despite the error "being ignored". The AX given to the critical error handler explains the different behavior. On FreeDOS, bit 5 of AH ist set, so it allows the error to be ignored. On MS-DOS and EDR-DOS this bit is cleared, and IGNORE is treated as a FAIL. So I consider this to be an incompatibility, and it should therefore be classified as a kernel bug. FreeDOS critical error return = 0 (IGNORE): creating file (INT21.3C) critical error AX=3800H critical error AX=3800H critical error AX=3900H handle: 5 writing to file (INT21.40) critical error AX=3800H critical error AX=3800H bytes written: 5 -- system hangs -- FreeDOS critical error retorn = 3 (FAIL): creating file (INT21.3C) critical error AX=3800H IO Error: 3 MS-DOS 3.31 critical error return = 0 (IGNORE): creating file (INT21.3C) critical error AX=1A00H IO Error: 3 MS-DOS 3.31 critical error retorn = 3 (FAIL): creating file (INT21.3C) critical error AX=1A00H IO Error: 3 EDR-DOS critical error return = 0 (IGNORE): creating file (INT21.3C) critical error AX=1800H IO Error: 83 EDR-DOS critical error retorn = 3 (FAIL): creating file (INT21.3C) critical error AX=1800H IO Error: 83 _______________________________________________ Freedos-devel mailing list Freedos-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-devel
