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.
This implements the principle of "least surprise", in that users won't
normally expect to start overwriting an existing file on these devices.
Real hardware didn't behave that way. A new (empty) file can always
be created with the -N switch on the ATTACH.
The -A attach time switch implicitly means to open files in append
mode.
Some devices used -A to indicate ASCII data or AUTOSIZE of disk or
fixed size tapes - DECtape. These devices are either read only devices
(Paper tape readers or card readers), so explicit forcing of the attach
to be -R avoids unexpected positioning errors. The random access
Disk and fixed sized tapes buffer the container contents in memory
so append mode isn't relevant, but care must be taken to assure that
the buffer reading starts at the beginning of the file without regard
to the explicit open mode.
As reported in #821
When dynamic loading readline, it intenally defines/references a variable
named PC which collides with a simulator defined global variable and
readline doesn;'t work for SCP ommand recall and possibly interferes with
simulator operation.
Most history routines defined a local sim_eval of the proper length, but the
erroneous ones were fixed length machines that defined an integer variable
instead of an integer array of length 1. The VAX used the global sim_eval.
The changes follow the VAX practice.
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.
Cleanup/Simplification by:
1) removing irrelevant master flag variable from sim_close_sock and thus sim_err_sock
2) change previous boolean feature arguments (datagram, nodelay, reuseaddr) to flag bits in a single option argument. This allows for features to be added by new flag bits which don't change the calling signatures.
3) changed all status returns to be int (vs t_stat) with success being 0 and error being -1
4) removed unneeded simh specific type references to allow sim_sock to be used by n
Extended API by providing flags to influence socket setup/behavior:
SIM_SOCK_OPT_REUSEADDR Retains prior behavior when sim_switches had -U set
SIM_SOCK_OPT_DATAGRAM UDP socket setup provided for when prior datagram argument was specified
SIM_SOCK_OPT_NODELAY TCP Nagle disable provided for when prior nodelay argument was specified
SIM_SOCK_OPT_BLOCKING Blocking socket mode (detault is non blocking)
This summer a group of us worked together to resurrect the original ARPAnet IMP software, and I’m now happy to say that the IMP lives again in simulation. It’s possible to run the original IMP software on a modified version of the H316 simh and to set up a virtual network of simulated IMPs talking to each other. IMP to IMP connections, which would have originally been carried over leased telephone lines, are tunneled over IP. As far as we can tell, everything works pretty much as it did in the early 1970s. IMPs are able to exchange routing information, console to console communications, network statistics, and they would carry host traffic if there were hosts on the network. The hooks are in there to allow simh to support the IMP side of the 1822 host interface, and the next step would be to recover the OS for an ARPAnet era host and then extend the corresponding simulator to talk to the IMP simulation.
Fixes several bugs described several months ago on the simh list about how the hardware really works, most notably the "dummy" cycle created by an OCP '1 (switch to output mode). In addition, it fixes other problems (OCP '0 and OCP '1 are unconditional) and adds a "busy"
state on character input, like the real hardware.
