Fix exec command

[diggit]

If exec_command is called before open, DLL opens connection to some probe it picks, which then causes issues when open is called afterwards.

resolves #254

[hkpeprah]

I'm not sure this is universally true. I believe it depends on the command being used. For example, I have no debugger attached and am able to do this:

import pylink
>>> jl = pylink.JLink()
>>> jl.disable_dialog_boxes()

[diggit]

If I revert back, detached J-Link and do...

import pylink
import time

jl = pylink.JLink()
jl.disable_dialog_boxes()
time.sleep(1)

...and nothing else. I get "probe selection" popup window. J-Link SW 9.20.
I hit esc multiple times and then I see

API Error: API JLINK_ExecCommand function called before JLINKARM_Open()
API Error: API JLINK_ExecCommand function called before JLINKARM_Open()
fish: Job 1, './experiments.py' terminated by signal SIGSEGV (Address boundary error)

in the stdout.

Then I tried each exec_command from disable_dialog_boxes individually.
Do not cause error and following open works normally:

• self.exec_command('SilentUpdateFW')
• self.exec_command('SuppressInfoUpdateFW')
• self.exec_command('SetBatchMode = 1')
• self.exec_command("SuppressControlPanel")

Cause error (need probe opened, auto calls open when the probe is attached):

• self.exec_command("HideDeviceSelection = 1")
• self.exec_command("DisableInfoWinFlashDL")
• self.exec_command("DisableInfoWinFlashBPs")

[hkpeprah]

Could you provide some details about your setup? Is this on Windows, Linux or OSX? It could be possible that behaviour is changed in later versions of the SDK and/or that behaviour depends on some combination of command + platform + SDK version.

[diggit]

My setup is mostly described on #254.
In summary:
OS: Archlinux (up to date)
J-Link 9.14a, 9.16, 9.20
Probe: J-Link Base compact 12.0

I would suspect the change of behavior in some recent dll.

[dottspina]

Faced with the same problem as #254 when working with pyOCD (nRF52840-DK), I too had started to look into it (in short, pyOCD also calls disable_dialog_boxes() before open(), see pyocd/pyOCD#1927 ).

@diggit, my findings seem to confirm yours (my OS is also Linux):

• I can reproduce the error with all versions above v9.12 of JLink DLL, tested with anything available from 9.14a to 9.24.
• the commands in disable_dialog_boxes() that trigger automatic connections are "HideDeviceSelection = 1" , "DisableInfoWinFlashDL" and ""DisableInfoWinFlashBPs"
• adding the @open_required decorator to JLink.exec_command() fixes the issue

Although opening the emulator may not be required for all commands, I support this merge request (AFAICT).
I even think it should be backported to the 1.7 branch: pyOCD requires pylink-square>=1.0,<2.0 and is affected by this issue.

A question: is calling disable_dialog_boxes() before open() considered a bad practice anyway ?

Thanks.

[hkpeprah]

@dottspina Thanks for the additional metric. @diggit , I've been thinking about how to approach this without making open_required required before disabling any of the dialog boxes. I wonder if we can workaround this with a state variable and some tracking in the .open() method? From a high level:

• Set a _disable_dialog_boxes: bool = False state variable in open().
• In disable_dialog_boxes(), check if the SDK version is >= the known breaking version and skip the specific calls @dottspina called out if the debugger connection has not been opened yet, but set _disable_dialog_boxes to True
• In open(), call disable_dialog_boxes() after opening the debugger connection if _disable_dialog_boxes is True, then set it to False.
• In enable_dialog_boxes(), clear the _disable_dialog_boxes (set to False).

What do you think? I think this would make the behaviour transparent to those who upgrade to newer SDK versions while preserving existing behaviour for those on older SDKs.

[diggit]

That sounds good!
How would you handle this scenario?

• disable_dialog_boxes()
• enable_dialog_boxes()
• disable_dialog_boxes()
• enable_dialog_boxes()
• open()

a) defer whole sequence (easiest to implement)
b) deduplicate calls of same functions and defer

• open()
• disable_dialog_boxes()
• enable_dialog_boxes()

c) deduplicate calls of same functions and collapse complementary calls and defer

• open()
• enable_dialog_boxes()

d) ?

[hkpeprah]

I wouldn't worry about de-duplicating the calls made. On Windows, some dialog boxes will open when you do open(), so we want those boxes to still be hidden, so I would just gate the specific ones that fail in the new SDK on the version check if not opened:

def disable_dialog_boxes():
    <disable dialogs that do not fail in new SDK w/o open>

    if <sdk_version < breaking_version> or <jlink opened>:
        <disable remaining dialog boxes>