Working on the tickets to implement the new defects handling, Tim Jenness implemented a new class to hold lists of defects. This seems to not be playing well in some very specific circumstances.

Specifics:
I never see segmentation faults on Linux.
On mac OS I've seen a segmentation fault on High Sierra running v10.1 of command line tools.
I have also seen a segmentation fault on Mojave running v10.2.1 of command line tools, but not when running v10.1.

To repeat:
1) setup w_2019_24
2) setup master of:

• obs_test_data
• obs_decam_data

3) setup tickets/DM-18739 of:

• obs_base
• obs_test
• pipe_tasks

4) setup tickets/DM-19730 of:

• obs_decam
• testdata_decam

5) Navigate to a location where an output repository can be created.
6) Execute (on some systems, this will result in a segmentation fault in the measurement phase in the calibrate task):

processCcd.py $TESTDATA_DECAM_DIR/rawData --output tmp_out --id visit=229388 ccdnum=1 --calib $TESTDATA_DECAM_DIR/rawData/cpCalib --config calibrate.doPhotoCal=False calibrate.doAstrometry=False

7) Remove output repository and rerun with defect interpolation turned off. This does not result in a segmentation fault on my system.

processCcd.py $TESTDATA_DECAM_DIR/rawData --output tmp_out --id visit=229388 ccdnum=1 --calib $TESTDATA_DECAM_DIR/rawData/cpCalib --config calibrate.doPhotoCal=False calibrate.doAstrometry=False isr.doDefect=False

I isolated things a little by running calibrate.py on the persisted outputs of IsrTask and CharImageTask and did not observe a segmentation fault.

I did more looking and if I modify the defects sent to IsrTask, I can get rid of the segmentation fault:

• Send an empty Defects – No segmentation fault
• Drop the last three defects from the list – No segmentation fault
• Drop the first three defects from the list – Segmentation fault
• Delete the python object that holds the defects immediately after interpolating – Segmentation fault.

Here is the backtrace from my terminal is attached.