RTAI build fails on branch master

[hdiethelm]

In context with #3870, I figured I could just set up a VM and run RTAI in there to implement also RTAI suport.

However, on master, the build fails.
Branch 2.9, all is fine:

• ./autogen.sh
• ./configure --with-realtime=/usr/realtime-5.4.279-rtai-amd64
• make -j8

Branch master, it fails:

• ./autogen.sh
• ./configure --with-realtime=/usr/realtime-5.4.279-rtai-amd64
• make -j8

libnml/posemath/_posemath.c:32:10: fatal error: rtapi_math.h: Datei oder Verzeichnis nicht gefunden
   32 | #include <rtapi_math.h>

[BsAtHome]

Can you rerun with: make V=1 and post the resulting output of the compile command and error?

Also, please check that you have [basedir]/include/rtapi_math.h in there (that should be a copy from the src/rtapi directory).

[hdiethelm]

What is [basedir]?

It seams to be the include paths are messed up:
Master:

Compiling libnml/posemath/_posemath.c
gcc -c -I. -Iemc -I/usr/realtime-5.4.279-rtai-amd64/../include -I/usr/include/python3.13 -I/usr/include/tirpc  -O2 -fwrapv  -g -Wall -D_FORTIFY_SOURCE=2 -DULAPI -std=gnu11 -Werror=implicit-function-declaration    -fPIC \
	-MP -MD -MF "objects/libnml/posemath/_posemath.d" -MT "objects/libnml/posemath/_posemath.o" \
	libnml/posemath/_posemath.c -o objects/libnml/posemath/_posemath.o
libnml/posemath/_posemath.c:32:10: fatal error: rtapi_math.h: Datei oder Verzeichnis nicht gefunden
   32 | #include <rtapi_math.h>
      |          ^~~~~~~~~~~~~~
compilation terminated.

2.9:

Compiling libnml/posemath/_posemath.c
gcc -c -I. -Ilibnml/linklist -Iemc -Ilibnml/cms -Ilibnml/rcs -Ilibnml/inifile -Ilibnml/os_intf -Ilibnml/nml -Ilibnml/buffer -Ilibnml/posemath -Irtapi -Ihal -Iemc -Iemc/nml_intf -Iemc/kinematics -Iemc/tp -Iemc/motion -Iemc/ini -Iemc -Iemc/rs274ngc -Iemc/sai -Iemc/pythonplugin -Iemc/tooldata -Iemc -I/usr/realtime-5.4.279-rtai-amd64/include -I/usr/include/python3.13 -I/usr/include/tirpc  -Os -fwrapv  -g -Wall -D_FORTIFY_SOURCE=2  -DULAPI -std=gnu11 -Werror=implicit-function-declaration   -fPIC \
	-MP -MD -MF "objects/libnml/posemath/_posemath.d" -MT "objects/libnml/posemath/_posemath.o" \
	libnml/posemath/_posemath.c -o objects/libnml/posemath/_posemath.o

Same for master and 2.9:

linuxcnc-src/src$ find .. -name rtapi_math.h
../include/rtapi_math.h
../src/rtapi/rtapi_math.h

[hdiethelm]

Anyway, it looks like RTAI on debian trixie is not that well supported. With 5.4.279-rtai-amd64 I had to add:
sd_mod
to /etc/initramfs-tools/modules and run update-initramfs to be able to boot.

[BsAtHome]

The -I paths got trimmed completely in master because includes were a big mess.

The problem is -I/usr/realtime-5.4.279-rtai-amd64/../include which is an expansion of Makefile:248: INCLUDE := $(patsubst %,-I%, $(INCLUDES)) -I$(RTDIR)/../include.

The RTDIR seems to be the problem. For the compile that should be the base directory of the LCNC source tree, but it is obviously the wrong macro. Take a look in Makefile.inc what is actually pointing correctly to the LCNC base directory in a RTAI build and share that with us.

And, FWIW, RTAI is beginning to become problematic because upstream is effectively dead and everybody moved on. There are essentially stock kernel RT_PREEMPT and Xenomai left and I don't think anybody has tried Xenomai v3 recently either (and it would need to be ported to version 4).

[BsAtHome]

Oh, and [basedir] is where the LinuxCNC source tree lives (where you extracted or cloned it).

[hdiethelm]

Ah so basically RTAI is dead and for Xenomai3 it would take some effort to even figure out how to build it. At least I found no good manual.
So it doesn't make sense to add RTAI or Xenomai3 support for #3870 if pretty much no one uses these variants.

[BsAtHome]

RTAI is less dead than Xenomai3 afaik. There are still users. Often "install once, forget what and why you did that" systems ;-)
@andypugh still likes to keep RTAI alive, for now, but we all know it will be on borrowed time.

That said, it looks like this particular issue, the wrong or missing -I include is fixable with relative ease. You need to include the LinuxCNC include directory for compiling the source. Maybe you can try to add -I ../include to the Makefile on line 248. The sources are supposed to be built from the src directory and the includes are located at src/../include. So that should work (cross fingers).