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.