#862 ngspice-47 segfaults when an invalid OSDI .model card follows a valid card

[Xuanhao Bao]

ngspice segfaults when an invalid OSDI .model card is declared after a valid
card. Changing only the order of the model cards changes a clean error into a
crash.

I have attached four files:

• demo_diode.va: minimal Verilog-A model; parameter n has the valid range
  (0:10).
• demo_diode.osdi: compiled x86-64 OSDI model.
• clean_invalid_then_valid.cir: reports Parameter n is out of bounds! and
  exits cleanly.
• crash_valid_then_invalid.cir: segfaults with exit code 139.

Both netlists use the same invalid value, n=100. Only the order of the two
.model cards differs. Load demo_diode.osdi before running the netlists.

I reproduced this with ngspice-44.2 and ngspice-47 on Linux x86-64.

I believe the bug is in OSDIsetup() in src/osdi/osdisetup.c. After
setup_model() fails, continue skips initialization for the failed model, and
a later successful model overwrites the error stored in res. The simulation
then proceeds with uninitialized Jacobian pointers and crashes in
load_jacobian_resist.

[Holger Vogt]

Thanks for the report.

Is there any reason (from user perspective) to not bail out immediately in case of such a model parameter error?

[Xuanhao Bao]

I think it would be perfectly reasonable to fail immediately once an
invalid model parameter is detected.

[Holger Vogt]

I have uploaded a fix to ngspice git branch pre-master-48.