Rootls could not load cppyy_backend library

ROOT
1

ROOT Version: 6.36.04
Platform: macosxarm64
Compiler: clang-1700.3.19.1

I compiled ROOT from source on my MacBook and general it all works ok (both CLING and usage from python). But when I try to run “rootls” in a terminal with a ROOT file I get the following errors:

rootls ../Lecture1/tree2.root

Traceback (most recent call last):

  File "/opt/hep/root/v6-36-04/bin//rootls", line 10, in <module>

    import cmdLineUtils

  File "/opt/hep/root/v6-36-04/lib/cmdLineUtils.py", line 79, in <module>

    import ROOT

  File "/opt/hep/root/v6-36-04/lib/ROOT/\__init_\_.py", line 25, in <module>

    import cppyy

  File "/opt/hep/root/v6-36-04/lib/cppyy/\__init_\_.py", line 88, in <module>

    from .\_cpython_cppyy import \*

  File "/opt/hep/root/v6-36-04/lib/cppyy/\_cpython_cppyy.py", line 24, in <module>

    c = loader.load_cpp_backend()

  File "/opt/hep/root/v6-36-04/lib/cppyy_backend/loader.py", line 100, in load_cpp_backend

    raise RuntimeError("could not load cppyy_backend library, details:\\n%s" %

        '\\n'.join(\['  '+x for x in err\]))

**RuntimeError**: could not load cppyy_backend library, details:

  dlopen(libcppyy_backend.cpython-313-darwin.so, 0x000A): tried: 'libcppyy_backend.cpython-313-darwin.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OSlibcppyy_backend.cpython-313-darwin.so' (no such file), '/opt/homebrew/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/opt/homebrew/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/usr/lib/libcppyy_backend.cpython-313-darwin.so' (no such file, not in dyld cache), 'libcppyy_backend.cpython-313-darwin.so' (no such file)

  dlopen(/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.cpython-313-darwin.so, 0x000A): tried: '/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.cpython-313-darwin.so' (no such file), '/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.cpython-313-darwin.so' (no such file)

  dlopen(/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.so, 0x000A): tried: '/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.so' (no such file), '/opt/hep/root/v6-36-04/lib/cppyy_backend/lib/libcppyy_backend.so' (no such file)

  dlopen(libcppyy_backend.so, 0x000A): tried: 'libcppyy_backend.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OSlibcppyy_backend.so' (no such file), '/opt/homebrew/lib/libcppyy_backend.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/lib/libcppyy_backend.so' (no such file), '/opt/homebrew/lib/libcppyy_backend.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OS/opt/homebrew/lib/libcppyy_backend.so' (no such file), '/usr/lib/libcppyy_backend.so' (no such file, not in dyld cache), 'libcppyy_backend.so' (no such file)

I can see this library does exist in my ROOT install:

find /opt/hep/root/v6-36-04/ -name 'libcppyy_backend\*'

/opt/hep/root/v6-36-04/lib/libcppyy_backend.so

and that is in my DYLD_LIBRARY_PATH:

echo $DYLD_LIBRARY_PATH

:/opt/hep/root/v6-36-04/lib

Am I missing that I should do something else in setup for this to work? Or if not what else could be the issue?

I built ROOT with the following cmake setup:

cmake -DCMAKE_INSTALL_PREFIX=/opt/hep/root/v6-36-04  /Users/markhodgkinson/root_src_Sep2025 -GNinja \\

  -DCMAKE_BUILD_TYPE=Release \\

  -DCMAKE_CXX_STANDARD=17 \\

  -Dfail-on-missing=ON \\

  -Dgdml=ON \\

  -Dx11=ON \\

  -Dpyroot=ON \\

  -Ddataframe=ON \\

  -Dmysql=OFF \\

  -Doracle=OFF \\

  -Dpgsql=OFF \\

  -Dsqlite=OFF \\

  -Dpythia6=OFF \\

  -Dpythia8=OFF \\

  -Dfftw3=OFF \\

  -Dbuiltin_cfitsio=ON \\

  -Dbuiltin_xxhash=ON \\

  -Dbuiltin_afterimage=OFF\\

  -Dbuiltin_openssl=OFF \\

  -Dbuiltin_ftgl=ON \\

  -Dbuiltin_glew=ON \\

  -Dbuiltin_gsl=ON \\

  -Dbuiltin_gl2ps=ON \\

  -Dbuiltin_xrootd=ON \\

  -Dgfal=OFF \\

  -Ddavix=ON \\

  -Dbuiltin_vdt=ON \\

  -Dxrootd=OFF \\

  -Dtmva=ON

Cheers,

Mark

2

Maybe @silverweed has an idea about what can be the issue…

3

Hello @Mark_C_Hodgkinson,

you may have to set the PYTHONPATH to the same directory for python to find the library. Does this solve the problem?

4

Hello,

It seems my PYTHONPATH already points there, so that won’t help:

echo $PYTHONPATH

:/opt/hep/root/v6-36-04/lib

Cheers,

Mark

5

Unfortunately I can’t say much about 6.36 as it’s still using the Python-based rootls, which I’m not very familiar with. All I can say is that this won’t be an issue anymore starting from 6.38 which replaces it with a native version (but that doesn’t solve OP’s problem)…