libgpiod_1.3 fails when building Python bindings (cannot find Python.h)

[harrymander]

Building libgpiod 1.3 with the Python bindings enabled on warrior. do_compile fails with this error:

| ../../../libgpiod-1.3/bindings/python/gpiodmodule.c:8:10: fatal error: Python.h: No such file or directory
|  #include <Python.h>

[kraj]

@HarryManderTait do have Python.h in recipe staging sysroot ?

[harrymander]

@kraj Yes: under recipe-sysroot/usr/include/python3.7m/Python.h

[kraj]

OK I think this could be a missing pkgconfing file or something, lets see if we can reproduce it

[harrymander]

The issue seems to be from the conditional inherit in the recipe file. The python3native class wasn't being inherited because the inline Python function is expanded before python3 is appended to PACKAGECONFIGS. See https://www.yoctoproject.org/docs/2.7/mega-manual/mega-manual.html#inherit-directive:

An advantage with the inherit directive as compared to both the include and require directives is that you can inherit class files conditionally. You can accomplish this by using a variable expression after the inherit statement. Here is an example:
inherit ${VARNAME}
If VARNAME is going to be set, it needs to be set before the inherit statement is parsed. One way to achieve a conditional inherit in this case is to use overrides:

Removing the conditional inherit and just inheriting python3native worked for me:

--- a/meta-oe/recipes-support/libgpiod/libgpiod_1.3.bb
+++ b/meta-oe/recipes-support/libgpiod/libgpiod_1.3.bb
@@ -9,7 +9,7 @@ PACKAGECONFIG[cxx] = "--enable-bindings-cxx,--disable-bindings-cxx"
 PACKAGECONFIG[tests] = "--enable-tests --enable-install-tests,--disable-tests --disable-install-tests,kmod udev"
 
 PACKAGECONFIG[python3] = "--enable-bindings-python,--disable-bindings-python,python3"
-inherit ${@bb.utils.contains('PACKAGECONFIG', 'python3', 'python3native', '', d)}
+inherit python3native
 
 PACKAGES =+ "${PN}-python"
 FILES_${PN}-python = "${PYTHON_SITEPACKAGES_DIR}"

[harrymander]

Not sure if this is the best way since python3native is being inherited even if the Python bindings aren't used. Perhaps my method of enabling the bindings is wrong? I am doing it by adding libgpiod_%.bbappend in a custom layer:

# recipes-support/libgpiod/libgpiod_%.bbappend
PACKAGECONFIG_append = " python3"

[kraj]

what you are doing is okay. We need to check if we can disable python during build or do we have to always build it and then maybe package it up separately.

[kraj]

@HarryManderTait The problem surfaces when your bbappend is doing _append operation. So I think the correct way to handle this is that we add python3 to default packageconfigs and then someone who does not need python3 enabled can do PACKAGECONFIG_remove = "python3" in their bbappend

I have posted a fix here [1], which should help address this issue, please try it in your case and then request a backport of it to warrior

[1] https://patchwork.openembedded.org/patch/164345/

[harrymander]

@kraj according to your patch python3native always be inherited. So why not just inherit it unconditionally and keep Python out of the default packageconfigs?

[kraj]

I think its fine to change defaults since the bindings go into the package of their own anyway,

[harrymander]

Patch works fine! Thanks.