Rebuilding native backend fails on raspberry pi

[cw150]

Expected Behavior

Using Edit->Options->Rebuild should build plutosdr backend

Actual Behavior

The plutosdr backend is not built, console log (omitting uninformative lines):
...
Found iio lib. Will compile with native plutosdr support
...
Skipping native support for plutosdr
...
usage: ExtensionHelper.py [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
or: ExtensionHelper.py --help [cmd1 cmd2 ...]
or: ExtensionHelper.py --help-commands
or: ExtensionHelper.py cmd --help

error: option -j not recognized

Steps To Reproduce

libiio was not found during urh install (with pip), probably because I installed it from source (it works with gnuradio). After installing libiio-dev package, it was still not found, due to unusual library path perhaps. I have to either specify /usr/lib/arm-linux-gnueabihf
in the urh options dialog, or run
export LD_LIBRARY_PATH=/usr/lib/arm-linux-gnueabihf
before running urh. Then I get the above behavior.

I am no python expert, this is how far I got in trying to fix this:

1. The "error: option -j not recognized" disappears if I comment line 285 in ExtensionHelper.py
   285c285
   < #sys.argv.append("-j{}".format(os.cpu_count()))

---

sys.argv.append("-j{}".format(os.cpu_count()))

---

The error in the console then becomes:
running clean
'build/lib' does not exist -- can't clean it
'build/bdist.linux-armv7l' does not exist -- can't clean it
'build/scripts-3.7' does not exist -- can't clean it

2. The problem seems to be with the way OptionsDialog.py calls ExtensionHelper.py. The first call to ExtensionHelper.get_device_extensions_and_extras in line 408 works, as seen by console output "Found iio lib. Will compile...". Then build_cmd is used to run ExtensionHelper.py in a subprocess. The main function will call get_device_extensions_and_extras a second time, however this time it will not find libiio. Apparently the additional library path is not passed when ExtensionHelper.py is invoked as a subprocess (and/or LD_LIBRARY_PATH has no effect). I checked that cythonize in line 290 is called with an empty list dev_extensions. This probably explains the "clean" error message.

Platform Specifications

• OS: Raspbian GNU/Linux 10 (buster) on raspberry pi 4
• URH version: 2.8.6
• Python version: 3.7.3
• Installed via pip

[cw150]

Problem solved by running urh as root. Sorry for the disturbance.