[LinuxCNC/linuxcnc Issue#145] check_config confused by gantry config

Using this config: https://github.com/SolidStateDepot/ssd-shopbot/tree/f0c39aa25a7d48da67e3c67c3bb3b22276fae79d

The .ini was auto-converted from a running, working 2.7 config to a JA-style config several months ago and not updated significantly since then. The machine ran fine with LinuxCNC 1:2.8.0~pre1.2239.gb97a1ca.

Tonight I updated LinuxCNC from the old working version of master to 1:2.8.0~pre1.2499.gd8ef5f7, and linuxcnc won’t start any more. It now gives this error:

> check_config: ERROR
> (Using identity kinematics: trivkins)
> [JOINT3]MINLIMIT > [AXISA]MINLIMIT (-0.250 > -1e99)
> [JOINT3]MAXLIMIT < [AXISA]MAXLIMIT (102.500 < 1e99) >
> check_config validation failed

This is a 4-joint, 3-axis gantry machine with “trivkins coordinates=xyzy”, so while it does have JOINT3, it does not have AXISA. Looks like a bug in check_config.tcl?

I worked around the problem by adding a bogus [AXIS_A] with compliant limits.