Ken's last note led me to look at magtape error handling, and it was
not right. This has resulted in a lot of code changes in sigma_mt.c, but
the changes are mostly mechanical. Instead of trying to be clever and
do channel handling in mt_map_err or at the bottom of the mt_svc
routine, every magtape command now does its own error handling.
This makes the code repetitive, but I hope it is much clearer as a result.
The problems all stem from a single root cause: when an interrupt is
requested - via any one of dozens of mechanisms (uend, normal end,
special request, error, etc), the interrupt routine must be presented
with the full device address, including the unit, which is stored in the
channel data structures. This is so that AIO (acknowledge interrupt)
can retrieve the unit number from the channel data structures and
give it back to the invoking program.
Unfortunately, service routines, error routines, etc were simply using
the base device address, which is good enough for all channel operations
EXCEPT AIO. So the four multi-unit device (RAD, DK, DP, MT) have had
changes to reconstruct the full device address, with unit number, before
any calls into the channel are made.
DP, funnily enough, required the fewest changes. Ken was exactly right
about the need to OR the unit number into dva at the start of the unit
service routine. That had to be done in a few more places where my code
was being lazy.
RAD, DK, MT required many more changes, but they were mostly mechanical.
All references to xx_dib.dva had to be examined and replaced with a full
device address. The full device address had to be reconstructed from the
UNIT pointer and the base device address, through the magic of pointer
arithmetic.
Another sore spot was HIO. HIO stops all the active unit in its tracks
and does a channel UEND on it. The calculation of the unit number in the
UEND was not correct in a few places, notably if DP did a controller reset.
Fixes for the four modules; an updated bug history; and an expanded
design document; are attached.
- TIO status routine always returns DVS_AUTO instead of proper status.
- DP_SEEK definition is off by 1.
- reset does not properly initialize controller, seek threads.
Historically this functionality was reimplemented within each
DEVICE simulator often with slightly different implementations
and inconsistencies. Solving this globally within SCP required
changes in many places, but should henceforth be reasonably
managed.
As discussed in #1034
- Fix static structure initialization
- Fix inconsistent statement indentations.
- Avoid potential out of array indexing due to theoretical array
reference via signed char index. Likely non functional change.
This avoids a potential invalid pointer dereference when formatting
the return value from sim_instr() if it is < SCPE_BASE but greater
than the previously defined static array size.sizeof
Update simh.doc to reflect this generic change.
These changes facilitate more robust parameter type checking and helps
to identify unexpected coding errors.
Most simulators can now also be compiled with a C++ compiler without
warnings.
Additionally, these changes have also been configured to facilitate easier
backporting of simulator and device simulation modules to run under the
simh v3.9+ SCP framework.
This reverts commit 5551a0dd9c.
The original idea was that the state being put into simh registers would be required to have all useful information available when remote console executed commands. These steps were taken from the code that sim_instr() executed as it was exiting. After this change was made it was realized that once a remote console command executed it might change state that directly affected instruction execution. To solve this, the logic that executes before the instructions in sim_instr() would then need to be executed whenever the event dispatch processing completed. This approach is messy, burdensome and potentially a lot of overhead for every event dispatch even though almost none of the event dispatches would be for remote console command execution. A completely different approach was suggested by J. David Bryan. That alternative approach would be to have remote console commands execute outside of the sim_instr() routine. Thus allowing the existing prelude and postlude code in sim_instr() to be performed naturally and let the remote console activities run in the same context as all other simh commands. Recent changes to scp and sim_console implement this alternative approach and thus these original changes are completely irrelevant and are thus being removed.
