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LinuxCNC controls CNC machines. It can drive milling machines, lathes, 3d printers, laser cutters, plasma cutters, robot arms, hexapods, and more.
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Loaded G-code program is executed on touch off in some kind of sandbox mode #2559

Closed petterreinholdtsen closed 1 year ago

petterreinholdtsen commented 1 year ago

I discovered a surprising feature of LinuxCNC I suspect is a bug. At least it break the principle of least surprise for me.

In short, the loaded G-code program is executed in some kind of sand box mode when pressing the touch off button in the GUI. I've tested this in Axis. To reproduce, save this simple g-code program as test-touch-off.ngc:

(msg, Did you expect this?)
(print, The value of parameter 1000 is #1000)
(msg, The value of parameter 1000 is #1000)
G53 G0 Z0
G53 G0 X0 Y0
M2

Next, load it into your LinuxCNC instance (for example a simulator of axis_mm, but it work on a physical instance too).

Press the 'Home All' button, and then press 'Z' followed by 'Touch Off'. Notice how the print and msg strings show up in stdout where linuxcnc was started and as notifications in the GUI.

The program was obviously executed at touch off, but the G0 instruction to move is ignored. I also discovered that the numbered parameter have different content while running in the 'touch off sandbox', and M66 return bogus pin values.

What is going on here?

rene-dev commented 1 year ago

This is most likely related to the 2 interpreter instances. One is in task, sending commands to motion, the other is running the preview.

andypugh commented 1 year ago

This is how the system knows to warn if the job does not fit inside the machine limits. And this needs to be recalculated after a touch-off. What is a surprise is that the messages get printed during the code check.

petterreinholdtsen commented 1 year ago

It would be less surprising if the "hidden run" was completely silent, or at least using the real numeric parameter values. It really threw me off that the numbers I was looking at suddenly were missing...

Btw, notice also how the (msg, The value of parameter 1000 is #1000) line do not print 0 for #1000, it prints '#1000' in the notification. Is this a bug? If so, I can create another issue for it.

andypugh commented 1 year ago

I think it is expected that (MSG, prints verbatim text and (DEBUG, expands parameters. (PRINT, is like (DEBUG, but outputs to stderr. http://linuxcnc.org/docs/2.9/html/gcode/overview.html#gcode:messages

rene-dev commented 1 year ago

It cannot use the same parameter set. Its a different instance in a different process. I Agree that the output can probably be improved. There is a parameter telling you which instance you are running in. This is used to hide toolchange related moves for example. Probably useful in debugging this.