[Bug 2048906] Re: [SRU] ngspice-36 crashes in various ways

[Dave Jones]

Confirmed the issue on jammy, patch looks good, so I'll sponsor this for
jammy. Thanks!

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https://bugs.launchpad.net/bugs/2048906

Title:
  [SRU] ngspice-36 crashes in various ways

Status in ngspice package in Ubuntu:
  Fix Released
Status in ngspice source package in Jammy:
  Confirmed

Bug description:
  [ Impact ]

  ngspice will sometimes crash on some trivial circuits and will result in Segmentation fault.
  Though upstream mentioned these types of circuits causing the segfault as "strange input".

  [ Test Plan ]

  * create a test file named "test.netlist" with the following content:
  .title KiCad schematic
  .save all
  .probe alli
  .end

  * execute "ngspice" command
  * run this command: "source test.netlist" on the ngspice prompt.

  With the fixed package it will print:

  Circuit: KiCad schematic

  [ Where problems could occur ]

  It is an upstream patch which only adds an check for a pointer before
  dereferencing it and there is a little chance of any regression
  because of this patch.

  [ Other Info ]

  The patch in the debdiff looks quite big due to the indentation
  changes but the real change is only:

  @@ -1130,6 +1130,7 @@ static char* get_terminal_number(char* e
      Called from inp.c*/
   void modprobenames(INPtables* tab) {
       GENinstance* GENinst;
  +    if (tab->defVmod) {
       for (GENinst = tab->defVmod->GENinstances; GENinst; GENinst = GENinst->GENnextInstance) {
           char* name = GENinst->GENname;
           /* Do not inlude the x in the new name, XU1 -> U1 */
  @@ -1159,4 +1160,5 @@ void modprobenames(INPtables* tab) {
               }
           }
       }
  +    }
   }

  [ Original Bug Description ]

  $ lsb_release -rd
  Description:	Ubuntu 22.04.3 LTS
  Release:	22.04

  ngspice version: 36+ds-1

  The following happens:
  =============================================

  ngspice is used by KiCad to simulate circuits.
  I have noticed that ngspice tends to crash or fail on relatively simple circuits.

  Taking KiCad out of equation I can see that even trivialities lead to
  crashes.

  For example, create a text file "test.netlist" with the following
  content:

  --- CUT ---
  .title KiCad schematic
  .save all
  .probe alli
  .end
  --- CUT ---

  Then start ngspice command line tool and run this command: "source
  test.netlist".

  The results would be this:

  --- CUT ---
  No compatibility mode selected!

  Circuit: KiCad schematic

  Segmentation fault (core dumped)
  --- CUT ---

  Other than segmentation faults, sometimes ngspice attempts to allocate
  a negative amount of memory (which also results in crashes).

  The following is expected:
  =============================================
  I expect that ngspice would not crash and would instead either do what it is asked to do or report errors.

  Suggested change:
  =============================================
  Update ngspice from version 3.6 to version 4.2: I have built v4.2 myself and checked - it appears to work or report genuine errors in all cases where the old ngspice simply crashes with no apparent reason.

  ProblemType: Bug
  DistroRelease: Ubuntu 22.04
  Package: ngspice 36+ds-1
  ProcVersionSignature: Ubuntu 6.2.0-35.35~22.04.1-generic 6.2.16
  Uname: Linux 6.2.0-35-generic x86_64
  NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  CurrentDesktop: GNOME
  Date: Wed Jan 10 14:32:41 2024
  InstallationDate: Installed on 2021-07-03 (921 days ago)
  InstallationMedia: Ubuntu-MATE 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
  RebootRequiredPkgs: Error: path contained symlinks.
  SourcePackage: ngspice
  UpgradeStatus: Upgraded to jammy on 2023-09-12 (119 days ago)

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