Inconsistency between ROOT documentation and build options actually enabled by default

[GiacomoXT]

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Description

While upgrading the ROOT version used for the Belle II software from 6.32 to 6.36, I found with great surprise that some build options that were supposed to be turned on by default according to https://root.cern/install/build_from_source/ were, instead, turned off. The two options I found are geom and tpython, which should be turned on in 6.36, but I found them turned off.

I spotted the options were turned off because some headers were not found while compiling our software against ROOT 6.36, e.g.: ls include/ | grep TPython and ls include/ | grep TGeoElement returned nothing (where include is the include directory with all the ROOT headers). This does not happen with ROOT 6.32.

Of course, I enabled successfully both geom and tpython with ROOT 6.36 by manually adding the options -Dgeom=ON and -Dtpython=ON.

One suggestion: when the ROOT configuration is printed at the end of cmake, it would be good to list ALL the enabled build options, both implicitly and explicitly enabled, so that the user can easily spot if anything is missing. I am referring to the line -- Enabled support for: builtin_clang builtin_cling builtin_ftgl builtin_gif builtin_gl2ps builtin_gsl builtin_jpeg builtin_llvm builtin_lz4 builtin_nlohmannjson builtin_pcre builtin_xxhash builtin_zstd dataframe http mathmore pyroot roofit runtime_cxxmodules shadowpw shared ssl tmva tmva-sofie x11 xml.

Reproducer

I will try to be brief...

1. I started a docker container using almalinux:9 as base image
2. I installed "few" packages: yum install --enablerepo=crb cmake emacs freetype-devel gcc gcc-g++ git glibc-devel libX11-devel libXext-devel libXft-devel libXpm-devel m4 make openssl openssl-devel protobuf protobuf-devel protobuf-compiler python3 python3-devel xz-devel wget which zlib-devel
3. I downloaded ROOT 6.36 source code using wget https://root.cern/download/root_v6.36.04.source.tar.gz and un-tared it
4. I compiled it with cmake SOURCE_DIR -DCMAKE_INSTALL_PREFIX=INSTALL_DIR -Dgminimal=ON -Dfail-on-missing=ON -DCMAKE_CXX_STANDARD=20 -DPython3_EXECUTABLE=/usr/bin/python3.9 -DPython3_INCLUDE_DIR=/usr/include/python3.9 -DPython3_LIBRARY=/usr/lib64/libpython3.9.so -Dasimage=OFF -Dbuiltin_freetype=OFF -Dbuiltin_ftgl=ON -Dbuiltin_gl2ps=ON -Dbuiltin_pcre=ON -Dbuiltin_xxhash=ON -Dbuiltin_zstd=ON -Dbuiltin_gif=ON -Dbuiltin_jpeg=ON -Ddataframe=ON -Dexception=ON -Dhttp=ON -Dmathmore=ON -Dmlp=ON -Dpyroot=ON -Droofit=ON -Dshadowpw=ON -Dshared=ON -Dssl=ON -Dtmva=ON -Dtmva-sofie=ON -Dvdt=OFF -Dxml=ON -Dbuiltin_nlohmannjson=ON -Dbuiltin_lz4=ON -Dbuiltin_gsl=ON -DCMAKE_CXX_FLAGS=-D__ROOFIT_NOBANNER && make -j 30

For ROOT 6.32, I repeated the same procedure, besides downloading https://root.cern/download/root_v6.32.14.source.tar.gz.

I don't think this is a OS-dependent issue, but I found the same issue with ubuntu:24.04.

ROOT version

v6.36.04

Installation method

Build from source

Operating system

Linux

Additional context

No response

[guitargeek]

Hi, thanks for the report!

One suggestion: when the ROOT configuration is printed at the end of cmake, it would be good to list ALL the enabled build options, both implicitly and explicitly enabled, so that the user can easily spot if anything is missing

This is already the case. Do you have other concrete suggestions to address this issue? Otherwise I don't really know what can be done here 🙂

I see the point that it's annoying if some features that were formerly part of ROOT minimal or gminimal get suddenly toggled with an option, because then people who start their configurations from (g)minimal will silently lose features. But how can this be done better? The only way I see is to keep this in mind for the future, and better highlight these cases in the release notes. I hope it will not happen often though!

[GiacomoXT]

Oh, now I see. I completely overlooked the -Dgminimal=ON flag in our setup... :( :( :(

Then I probably have nothing to report to ROOT. Maybe you could mark which options fall under (g)minimal?

[dpiparo]

@GiacomoXT that would be a really useful thing to do. I will take care.

[GiacomoXT]

@guitargeek @dpiparo did the "ROOT Configuration" start the report all the enabled options (implicitly and explicitly) since 6.34 or 6.36? Because I did not see geom and tpython in the reported list of 6.32, and thus my confusion and initial suggestion. 😅

[guitargeek]

Ah! I see, where the confusion is coming from then. As I hinted to before, these build options were only introduced in 6.34, which is why they are not listed in the configuration. There is no way for the older releases like 6.32 to know what future configurations options are, sorry 🙂

See:

• [cmake] modularize geom and geombuilder #16514
• Make it possible to disable TPython in build #16337

[GiacomoXT]

Fair. :D