[yocto] The BitBake equivalent of "Hello, World!"

[Rudolf Streif]

The T variable points to a directory were Bitbake places temporary files
when building a particular package. It is typically set to

T = ${WORKDIR}/temp

WORKDIR is the directory into which Bitbake unpacks and builds a package.
The default bitbake.conf file sets this variable.

T is not to be confused with TMPDIR which points to the root of the
directory tree where Bitbake puts the output of an entire build.

:rjs

On Mon, Oct 8, 2012 at 5:30 PM, Patrick Turley
<PatrickTurley at gamestop.com>wrote:

>  I am continuing my work on creating a "Hello, World!" BitBake project.
> Because of the excellent help I got before, things have gone reasonably
> well, but I'm again running into something I don't know how to fix.
>
>  As before, the entire contents of my very small project appear at the
> end of this message. Here's what works fine:
>
>
>      $ ../BitBake/bin/bitbake-layers show-layers
>     Parsing recipes..done.
>
>      layer     path                                    priority
>     ==========================================================
>     LayerA    /home/pturley/Workspace/Hello/LayerA    1
>
>      $ ../BitBake/bin/bitbake-layers show-recipes
>     Parsing recipes..done.
>     === Available recipes: ===
>     a:
>       LayerA               1
>
>
>  When I tried this:
>
>
>      ../BitBake/bin/bitbake -c listtasks a
>
>
>  I got a Python stack trace that ended here:
>
>
>        File "../BitBake/lib/bb/runqueue.py", line 902, in
> RunQueue.check_stamp_task(task=0, taskname='do_listtasks', recurse=False):
>                  # If the stamp is missing its not current
>         >        if not os.access(stampfile, os.F_OK):
>                      logger.debug(2, "Stampfile %s not available",
> stampfile)
>     TypeError: coercing to Unicode: need string or buffer, NoneType found
>
>
>  This code isn't expecting the "stampfile" variable to be "None" (which
> it is), so it freaks out. I made a very simple fix to get past the problem:
>
>
>      if not stampfile or not os.access(stampfile, os.F_OK):
>
>
>  That made a dramatic difference, and enabled me to get this far:
>
>
>      $ ../BitBake/bin/bitbake -c listtasks a
>     Loading cache: 100%
> |###############################################################| ETA:
>  00:00:00
>     Loaded 2 entries from dependency cache.
>     NOTE: Resolving any missing task queue dependencies
>     NOTE: Preparing runqueue
>     NOTE: Executing RunQueue Tasks
>     NOTE: Running task 1 of 1 (ID: 0, /home/pturley/Workspace/Hello/LayerA/
> a.bb, do_listtasks)
>     ERROR: T variable not set, unable to build
>     ERROR: Task 0 (/home/pturley/Workspace/Hello/LayerA/a.bb,
> do_listtasks) failed with exit code '1'
>     NOTE: Tasks Summary: Attempted 1 tasks of which 0 didn't need to be
> rerun and 1 failed.
>
>      Summary: 1 task failed:
>       /home/pturley/Workspace/Hello/LayerA/a.bb, do_listtasks
>     Summary: There was 1 ERROR message shown, returning a non-zero exit
> code.
>
>      $ ../BitBake/bin/bitbake a
>     Loading cache: 100%
> |###############################################################| ETA:
>  00:00:00
>     Loaded 2 entries from dependency cache.
>     NOTE: Resolving any missing task queue dependencies
>     NOTE: Preparing runqueue
>     NOTE: Executing RunQueue Tasks
>     NOTE: Running task 1 of 1 (ID: 0, /home/pturley/Workspace/Hello/LayerA/
> a.bb, do_build)
>     ERROR: T variable not set, unable to build
>     ERROR: Task 0 (/home/pturley/Workspace/Hello/LayerA/a.bb, do_build)
> failed with exit code '1'
>     NOTE: Tasks Summary: Attempted 1 tasks of which 0 didn't need to be
> rerun and 1 failed.
>
>      Summary: 1 task failed:
>       /home/pturley/Workspace/Hello/LayerA/a.bb, do_build
>     Summary: There was 1 ERROR message shown, returning a non-zero exit
> code.
>
>
>  As you can see, BitBake is expecting the "T" variable to be set.  I
> don't think I've ever seen this variable -- so I don't know what it's for
> or what I should change.
>
>  Can anyone offer a hint?
>
>
>  ------------------------------------------------------------
>
>
>  ├── build
> │   │
> │   ├── classes
> │   │   │
> │   │   └── base.bbclass
> │   │
> │   │       +-----------------------------------------------
> │   │       |  addtask listtasks
> │   │       |
> │   │       |  do_listtasks[nostamp] = "1"
> │   │       |
> │   │       |  python do_listtasks() {
> │   │       |          import sys
> │   │       |          # emit variables and shell functions
> │   │       |          #bb.data.emit_env(sys.__stdout__, d)
> │   │       |          # emit the metadata which isnt valid shell
> │   │       |          for e in d.keys():
> │   │       |                  if d.getVarFlag(e, 'task'):
> │   │       |                          bb.plain("%s" % e)
> │   │       |  }
> │   │       |
> │   │       |  addtask build
> │   │       |
> │   │       |  do_build() {
> │   │       |      echo "Hello"
> │   │       |  }
> │   │       +-----------------------------------------------
> │   │
> │   └── conf
> │       │
> │       ├── bblayers.conf
> │       │
> │       │   +-----------------------------------------------
> │       │   |  BBLAYERS ?= " \
> │       │   |    /home/pturley/Workspace/Hello/LayerA \
> │       │   |    "
> │       │   +-----------------------------------------------
> │       │
> │       └── bitbake.conf
> │
> │           +-----------------------------------------------
> │           |  CACHE = "${TOPDIR}/cache"
> │           +-----------------------------------------------
> │
> ├── LayerA
> │   │
> │   ├── a.bb
> │   │
> │   │       +-----------------------------------------------
> │   │       |  DESCRIPTION = "Layer A Main Recipe"
> │   │       |  PN = 'a'
> │   │       |  PV = '1'
> │   │       +-----------------------------------------------
> │   │
> │   └── conf
> │       │
> │       └── layer.conf
> │
> │           +-----------------------------------------------
> │           |  BBPATH .= ":${LAYERDIR}"
> │           |
> │           |  BBFILES += "${LAYERDIR}/*.bb"
> │           |
> │           |  BBFILE_COLLECTIONS += "A"
> │           |  BBFILE_PATTERN_A := "^${LAYERDIR}/"
> │           +-----------------------------------------------
> │
> └── BitBake
>
>     The BitBake directory origin is:
>
>         http://git.openembedded.org/bitbake/
>
>     I have the 1.15.2 tag checked out, which is what
>    Yocto denzil uses.
>
>
> _______________________________________________
> yocto mailing list
> yocto at yoctoproject.org
> https://lists.yoctoproject.org/listinfo/yocto
>
>
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