[Solved] Compile Error when using regular math functions in kinematics file

I used some math functions in a kinematics file. Things like abs, cos, acos, sin, asine and so forth.
When I try to build it I get this error:

Apparently its a problem with a missing library that needs to be added to the make file. The section for this kinematic file looks like this but I have really not much clue as to what would need to be added.



I would appreciate some guidance as to solve this.

please post the output from:

linuxcnc_info excerpts: So it appears to be debian stretch with preempt rt kernel.
I cannot reproduce on a similar 64bit stretch virtual machine
but need more information.

1) Are you modifying the primary in-tree Makefile (e.g. src/Makefile)?
or
2) Are you using an independent Makefile?

In either case, please explain in more detail and post:
a)the Makefile used to produce the error message posted at
message 158554
b)the exact directory location of the Makefile
c)the source file(s) using added math functions.

Note: you have both a git tree and a deb install for linuxcnc
and that can lead to hard-to-find errors.

Thanks so much for looking into this!

So I have uninstalled the deb in the synaptic manager and deleted all the RIP installations.

Then :
$ git clone git://github.com/linuxcnc/linuxcnc.git linuxcnc-dev
$ cd linuxcnc-dev/src
$ ./autogen.sh
$ ./configure --with-realtime=uspace

Returning the message to continue to compile by typing make ....

$ make && sudo make setuid

Build fails:

I tried this a couple of times but I can't build LinuxCNC anymore.

I'll try a fresh install and report back.

tried a fresh Linux Mint 19.1 install and the exact same thing happens when I try to build LinuxCNC from git.
Now I'll try an iso.

This just threw me on total loop! There must have been something wrong with the linuxcnc-dev on git. I tried about four different systems on two different machines until I decided to just forget about the normal branch and try to build the switchkins-branch.
Turns out that works just fine!
[strike]My kinematics file now also compiles without error.[/strike]

So I'm back to square 1 with this. Im on a new machine (Linux Mint 19.1 Tessa non realtime kernel)


I've made changes to these two files adding a third kinematics case in genser-switchkins.c which corresponds to a remap to M430. This seems to work.

Of course the difficult part is the actual code for the "gensertoolKinematicsInverse" function. Because I'm having a hard time making sense of all the pointers and go_math functions in the original code I'm trying to use a code by Rudy du Preez that should actually be able to do the toolcoordinate kinematics I want. So I copied that in. Since his code does not define any other includes I thought that would work. But when I rebuild I get the error:
Probably totally obvious to other people who actually know what they're doing but I'm stumped.
All hints are welcome.
Thanks

I found this answer to a similar question:

If your code includes mathematical functions (like exp, cos, etc.), you need to link to the mathematics library libm.so. This is done, just like for serial compiling, by adding -lm to the end of your compile command, that is,

mpicc -o sample sample.c -lm

But where would I add that "-lm"?