DOS ain't dead

(Copied from freedos-user mailing list announcement.)

Hello list,

I finished release 6 of lDebug (with a small L) today. This is my advanced 86-DOS debugger project based on FreeDOS Debug/X (in turn based on MS-DOS Debug), with some ideas from DR-DOS Debug. The duration since the prior release 5 is back to less than 6 months as opposed to the year between releases 4 and 5. Apart from the usual amount of bugfixes, there are some new features.

If the debugger is not bootloaded (that is, loaded as a DOS application or DOS device driver) then some of the boot-specific code and messages is discarded, saving some resident memory. The ATTACH command [1] does the opposite of the TSR command, allowing a device-mode debugger to attach to a process. The K command is a synonym to N usually, to stay compatible to my MSDebug build [2]. .HEX files can be read now.

Some features were suggested on the sourceforge.net FreeDOS feature tracker. These include style 2 and style 3 alternative symbolic flag displays [3]. The E, F, and S commands allow specifying lists with leading keywords like "AS WORDS" or "AS DWORDS" [4] [5]. The DT (dump text table) command [6] allows to generate an ASCII table [7], a table of the top half of the 8-bit space, or to dump the bytes of a specified number as text [8]. The H command displays the remainder if the outermost operator is a division [9].

Another feature suggested there [3] is the debugger will attempt to read a configuration file on startup now, either from the directory specified in the %LDEBUGCONFIG% variable, or else the same directory as the lDebug executable. This is described a bit in the manual section on "Invoking the debugger as an application" [10]. Further, when a Script for lDebug (.SLD) file is not found it is searched for in the directory specified by the %LDEBUGSCRIPTS% variable [12], or also the debugger executable directory.

The INSTALL and UNINSTALL commands were extended with many new nouns for reconfiguring the debugger [11] without having to look up cryptic numbers to set or clear in the Debugger Common Options (DCO) variables.

There is a new mode called RH mode [12], which allows the RH command [13] to replay any of the last several dozen register dumps from the debugger's auxiliary buffer. While on the topic of the auxiliary buffer, the application mode and device driver mode init of the debugger gained the ability to grow this buffer to up to 24 KiB, beyond its minimum size of just above 8 KiB. This is done by passing an /A switch to the debugger's init [10]. Because it is done in the init, this costs very little amounts of resident space.

Another two features are done in the debugger init, costing no space in the resident debugger. The first is the /P switch (or component /PE and /PS switches) to guess a filename extension and do a path search for the specified file. The second is a warning for an unknown filename extension, which can be disabled with a /PW- switch.

Finally, the default build of the debugger gained the run time option to install interrupt 0Dh and interrupt 0Ch handlers in Real/Virtual 86 Mode, using an INSTALL INTFAULTS command [11]. Most physical machines in Real 86 Mode, and the most recent dosemu2 VMM in Virtual 86 Mode, will dispatch faults in 86 Mode to these handlers. However, the same handlers are usually invoked for two different IRQs. The debugger's handlers will query the Programmable Interrupt Controller (PIC) to find out whether a corresponding IRQ is being serviced; if it is then the debugger will pass along the call to the downlink of its handler. Otherwise, it is treated as a fault.

The release packages are available from our server [14] as usual. The fdpkg subdirectory [15] has a FreeDOS package that I prepared. The svardpkg subdirectory [16] has executable and source SvarDOS packages. The repo history up to the release can be read in our hgweb [17]. The News chapter of the manual has a section on release 6 [18].

Regards,
ecm


[1]: https://pushbx.org/ecm/doc/ldebug.htm#cmdattach
[2]: https://pushbx.org/ecm/doc/msdebug.htm#cmdn
[3]: https://sourceforge.net/p/freedos/feature-requests/93/
[4]: https://sourceforge.net/p/freedos/feature-requests/102/
[5]: https://pushbx.org/ecm/doc/ldebug.htm#parlist
[6]: https://pushbx.org/ecm/doc/ldebug.htm#cmddt
[7]: https://sourceforge.net/p/freedos/feature-requests/105/
[8]: https://sourceforge.net/p/freedos/feature-requests/99/
[9]: https://sourceforge.net/p/freedos/feature-requests/100/
[10]: https://pushbx.org/ecm/doc/ldebug.htm#invoking-app
[11]: https://pushbx.org/ecm/doc/ldebug.htm#cmdinstall
[12]: https://sourceforge.net/p/freedos/feature-requests/118/
[13]: https://pushbx.org/ecm/doc/ldebug.htm#cmdrh
[14]: https://pushbx.org/ecm/download/ldebug/
[15]: https://pushbx.org/ecm/download/ldebug/fdpkg/
[16]: https://pushbx.org/ecm/download/ldebug/svardpkg/
[17]: https://hg.pushbx.org/ecm/ldebug/log/release6
[18]: https://pushbx.org/ecm/doc/ldebug.htm#news-r6

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