Fixed Cryptic Error Codes in mpStartJob

[aigallegos]

fixes #102. I wrote a new function that kept the error string format as an f-string for mpStartJob errors in MotionControl.c by just adding a new function called Ros_ErrorHandling_Only_ErrNo_ToString in ErrorHandling.c that did not use strncpy and therefore did not need a buffer to get passed in, similar to Ros_ErrorHandling_MotionNotReadyCode_ToString it just returns a char* instead of having a destination for the chars and can be directly passed into the error f-string.

[gavanderhoorn]

I wrote a new function that kept the error string format as an f-string for mpStartJob errors in MotionControl.c by just adding a new function called Ros_ErrorHandling_Only_ErrNo_ToString in ErrorHandling.c that did not use strncpy and therefore did not need a buffer to get passed in

thing is, that buffer & copy are needed, as functions can't return pointers to temporaries (ie: variables on the stack).

similar to Ros_ErrorHandling_MotionNotReadyCode_ToString it just returns a char* instead of having a destination for the chars and can be directly passed into the error f-string.

you could consider defining all error 'strings' as

static char something[] = "...";

which would allow just return-ing something directly.

Ros_ErrorHandling_MotionNotReadyCode_ToString(..) used to do this, but that's invisible now, as the storage for the 'strings' returned by it is the responsibility of the code generated by the ROS 2 message generators now.

[gavanderhoorn]

Turns out, string literals are treated differently from other locals. According to the C99 standard, they are automatically added to an anonymous array with static storage, so returning const char* const to elements should be OK. TIL.

(note: only literals get this treatment. Returning pointers to anything else on the stack would still be problematic)

@aigallegos: your initial implementation was already OK, so apologies for the noise.

I did remove the function you added though, as it was basically a duplicate of Ros_ErrorHandling_ErrNo_ToString(..) and updated your PR to now just call the updated Ros_ErrorHandling_ErrNo_ToString(..).

[gavanderhoorn]

Note: we should consider squash-merging this if possible. All my commits are essentially fix-ups.

I've implemented my own requested changes, need a fresh pair-of-eyes to review

[ted-miller]

Looks good.

THU 2023-08-03 15:03:27.596 Ros_MotionControl_StartMotionMode: enter
THU 2023-08-03 15:03:29.876 Can't start 'INIT_ROS' because: 'The home position is not registered' (0x3040)

Thank you both for the PR!

[gavanderhoorn]

Thanks @aigallegos 👍

[aigallegos]

Thanks @aigallegos 👍

Thank YOU! I learned so much from this rabbit hole we went down and thanks for putting up with my newbie negligence that just so happened to be correct haha. Thanks for the help and happy coding!

[gavanderhoorn]

If you see any other issues you believe you could help with, please comment on them and we can discuss potential approaches.