#395 segfault: jtag drscan <tapname> 32 1

[fenugrec]

On latest master (91bd43134) :

>  jtag drscan auto0.tap 32 1
Connection closed by foreign host.
*******
openocd: src/jtag/drivers/driver.c:166: interface_jtag_add_dr_scan: Assertion `field == out_fields + scan->num_fields' failed.
Aborted (core dumped)

[Paul Fertser]

Hi,

jtag drscan auto0.tap 32 1
Connection closed by foreign host.

---

openocd: src/jtag/drivers/driver.c:166: interface_jtag_add_dr_scan: Assertion `field == out_fields + scan->num_fields' failed.

This happens because basically all taps are in BYPASS by default, and
before manual "drscan" command you naturally need to do the
appropriate "irscan" on the same tap (as all DR operations are current
instruction-specific).

Guess we should introduce a special error message for the case.

[Paul Fertser]

On Fri, Apr 28, 2023 at 09:07:14PM -0000, fenugrec wrote:

jtag drscan auto0.tap 32 1
Connection closed by foreign host.

---

openocd: src/jtag/drivers/driver.c:166: interface_jtag_add_dr_scan: Assertion `field == out_fields + scan->num_fields' failed.
Aborted (core dumped)

Should be handled by https://review.openocd.org/c/openocd/+/7654

[fenugrec]

Thanks, good find !

[Antonio Borneo]

If you have any 'target' (a CPU to be debugged) in your config file, then OpenOCD will run continuously polling on the target to check if it has hit a breakpoint.
This polling can happen anytime, also within a sequence:
irscan ...
drscan ...
with the result that the IR is modified under the hood.
To prevent it, use the sequence
poll off
irscan ...
drscan ...
poll on