====== Early August work ======

**2023-08-06**

Some developments happened this week.


===== FreeDOS kernel changes for WIN31SUPPORT build option =====

[[https://retrocomputing.stackexchange.com/questions/27480/how-to-use-start-windows-3-11-with-freedos/27481?noredirect=1#comment97694_27481|In response to a stackexchange question]] on running MSWindows 3.11 in 386 Enhanced mode, I wanted to prepare a build of the latest kernel revision with its ''WIN31SUPPORT'' build option enabled.

However, I found that the sources with this option enabled used ''seg'' and ''wrt'' terms that NASM's elf output format does not support.

[[https://github.com/FDOS/kernel/pull/110|I added some conditional code to work around this]]. In kernel.asm this adds more variables and makes those and another global. In the interrupt 2Fh handler, the three new variables are filled with the segmented address parts they need.

I did check the result, but I do not know entirely that it is correct.

In one of the places, I found that a segmented far pointer is stored with the segment first. I do not know whether this is correct, but I left it as is.


===== FreeDOS mailing list reply on booting FreeDOS off an 8088 machine =====

I [[https://sourceforge.net/p/freedos/mailman/message/37880211/|prepared a long reply to the freedos-devel mailing list]] on how to boot off a CF card on an 8088 machine, but preparing the card on another machine. I basically presented three options:

  * Using SYS /FORCE:CHS to install the 8086-compatible, CHS FAT32 loader
  * Installing my lDOS boot loaders using the FreeDOS load protocol with the instsect application, which are all 8086-compatible.
  * Installing bootable lDebug, the boot loaders for which are also all 8086-compatible. Once the debugger is loaded it can be used to load and run the FreeDOS kernel.


==== Bonus ====

A while ago I wrote about [[https://sourceforge.net/p/freedos/mailman/message/37871507/|how to install FreeDOS to a logical partition]] and/or a partition that is not DOS's drive C:.


===== lDebug work =====

[[https://hg.pushbx.org/ecm/ldebug/rev/c46474e302cb|A bug in the S command]] accessing a byte behind its ''sss_silent_count_used'' variable was fixed.

The S command's SILENT keyword clause [[https://hg.pushbx.org/ecm/ldebug/rev/a3113ea02a0c|was documented]].

The S command's data dump's displacement display [[https://hg.pushbx.org/ecm/ldebug/rev/455eaca9561b|was documented]].

The /A= switch [[https://hg.pushbx.org/ecm/ldebug/rev/40e54cb4f0db|was documented]].

[[https://hg.pushbx.org/ecm/ldebug/rev/5e092e55e2e7|A new flag was introduced]] which controls whether serial I/O is used. [[https://hg.pushbx.org/ecm/ldebug/rev/f5dd19b537a6|Prior to that]], the DCO option was directly used to control this. Besides being a shoddy design, this led to a bug when running a command like ''install serial,timer,amis''. When this bug happened, the INSTALL command's output would try to use the buffers for serial output that were not initialised yet. This would make the debugger corrupt parts of its process as the pointers happened to be zero.

The /A= switch [[https://hg.pushbx.org/ecm/ldebug/rev/249809eec8a6|is now also supported when loading as a device driver]]. Largely this shares the code used for adjusting the history segment and the code segments for the application mode /A= switch. However, it also needs [[https://hg.pushbx.org/ecm/ldebug/rev/f3cb7d3933ae|to rewrite a convenience signature]] at the end of the debugger's allocation and adjust the device driver size in one debugger variable as well as in the device request header passed by the DOS.

The RH command keyword COUNT [[https://hg.pushbx.org/ecm/ldebug/rev/7b9f99667bee|allows to display the RH step number]] for every displayed step, in hexadecimal [[https://hg.pushbx.org/ecm/ldebug/rev/42f926090d45|and decimal]].

There are [[https://hg.pushbx.org/ecm/ldebug/rev/9b30ab5522bf|more places]] which [[https://hg.pushbx.org/ecm/ldebug/rev/962c82ba837d|accept commas as separators]].

There is a new command, CLEAR, to attempt to clear the screen. This is done [[https://hg.pushbx.org/ecm/ldebug/rev/397bf8e0dbf9|by emitting two escape sequences]]. If the output is to a ROM-BIOS int 10h interface and the application is not running in a ''-dumb'' mode dosemu2 then one of the escape sequences is [[https://hg.pushbx.org/ecm/ldebug/rev/ea1053509650|translated into int 10h calls]] to blank the screen and reset the cursor position.

Finally, the D strings commands were changed [[https://hg.pushbx.org/ecm/ldebug/rev/ab6da3216dc3|to buffer their outputs]] into ''line_out'' instead of calling ''getc'' for every single byte. This improves the performance, but also allows the debugger's escape sequences for inverting the display attributes and for clearing the screen to be used by the D strings commands' output. (These escape sequences must be passed in full to a single ''puts'' call in order to be recognised.)


{{tag>fdkernel ldosboot ldebug}}


~~DISCUSSION~~