[core] Use automatic build tree detection for all resource directories by guitargeek · Pull Request #21018 · root-project/root

guitargeek · 2026-01-25T15:04:48Z

This follows up on a5b1ed9, using the mechanism to automatically detect if we are in the build tree or install tree also for the other resource directories (so far it was only implemented for the include directory as a first test).

Several fallbacks and hacks can be removed because of this change, like the ROOTIGNOREPREFIX variable that was needed to run ROOT in the build tree for the tests.

This change also makes ROOT completely independent of the ROOTSYS environment variable and therefore unblocks #20006.

If one wants to check that all the resource directories (inlcuding RootSys()) are correct, one can use this check:

void checkdirs() {

    std::cout << "Bin       : " << gROOT->GetBinDir() << std::endl;
    std::cout << "Data      : " << gROOT->GetDataDir() << std::endl;
    std::cout << "Doc       : " << gROOT->GetDocDir() << std::endl;
    std::cout << "Etc       : " << gROOT->GetEtcDir() << std::endl;
    std::cout << "Icon      : " << gROOT->GetIconPath() << std::endl;
    std::cout << "Include   : " << gROOT->GetIncludeDir() << std::endl;
    std::cout << "Lib       : " << gROOT->GetLibDir() << std::endl;
    std::cout << "Macro     : " << gROOT->GetMacroDir() << std::endl;
    std::cout << "RootSys   : " << gROOT->GetRootSys() << std::endl;
    std::cout << "SharedLib : " << gROOT->GetSharedLibDir() << std::endl;
    std::cout << "TTFFont   : " << gROOT->GetTTFFontDir() << std::endl;
    std::cout << "Tutorial  : " << gROOT->GetTutorialDir() << std::endl;
}

github-actions · 2026-01-25T20:33:10Z

Test Results

21 files 21 suites 3d 20h 48m 28s ⏱️
3 866 tests 3 841 ✅ 1 💤 24 ❌
73 528 runs 73 270 ✅ 232 💤 26 ❌

For more details on these failures, see this check.

Results for commit 6dde01e.

♻️ This comment has been updated with latest results.

vepadulano · 2026-01-29T16:20:03Z

https://github.com/root-project/root/actions/runs/21481040637/job/61888781030?pr=21018#step:7:18 This error probably means that ROOT cannot even start and the process segfaults.

guitargeek · 2026-01-30T13:03:02Z

https://github.com/root-project/root/actions/runs/21481040637/job/61888781030?pr=21018#step:7:18 This error probably means that ROOT cannot even start and the process segfaults.

This is fixed by that PR:

[build] Use CMAKE_INSTALL_<dir> variables consistently in setup.py #21075

This is to test that ROOT doesn't get confused at build and test time by the fact that the structure of the install tree and build tree is different, which is the case for `gnuinstall=ON`.

pcanal · 2026-06-18T17:15:15Z

Updating master merge/rebase point

pcanal · 2026-06-18T17:17:16Z

@@ -1,15 +1,14 @@
-/* This file is automatically generated */


Why remove this?

I changed this file manually, so arguably the file is not automatically generated anymore. Also how did this comment help without saying how the file was automatically generated? 🙂

The comment is one off in this context :). The file compiledata.win32.in is hand written but used as a template for the generation of compiledata.h and in the that file the comment is accurate :)

Oh okay I get what you mean now! I'll add the comment back

pcanal · 2026-06-18T17:30:16Z

  endif()
-  file(RELATIVE_PATH install_lib_to_include "${libdir}" "${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}")
-  unset(libdir)
+  file(RELATIVE_PATH _rel "${libdir}" "${install_dir_absolute}")


What happens if libdir and install_dir_absolute are both absolute and unrelated (weird installation where one of the directory is being installed in an unusual place).

To keeps things simple and branch-free: every resource directory is encoded as a path relative to libdir, resolved at runtime against the actual location of libCore. So the whole install tree stays relocatable as long as its internal layout is preserved.

There might be corner cases where different behavior is preferable, e.g. an some absolute resource directory like /usr/etc directory outside the install prefix that you expect to stay fixed even when the build is relocated. There, a relative path would be wrong. But I think that's a pathological case we Shouldn't support unless a user actually asks for it.

To be fair, this would have worked before with gnuinstall=ON, because all resource directories were absolute in that case, but that also means gnuinstall=ON builds weren't relocatable. One of my goals here was to unify the gnuinstall=ON and gnuinstall=OFF behavior so they only differ by the CMAKE_INSTALL_<…> paths. So if you want relocatable builds and not too many if-else branches in the CMake, what's in the PR is the result..

We really do not have a good handle on whether the feature is or is not used (I do have some recollection of using stashing the etc and/or share directory 'somewhere' else). Unless I can re-find the user I am thinking of (and maybe even if), we really should "explicitly" error out if we can detect the issue.

This follows up on a5b1ed9, using the mechanism to automatically detect if we are in the build tree or install tree also for the other resource directories (so far it was only implemented for the `include` directory as a first test). Several fallbacks and hacks can be removed because of this change, like the `ROOTIGNOREPREFIX` variable that was needed to run ROOT in the build tree for the tests.

Example of how the warning looks like if it happens: ```txt [I] omen nix-shell ~/c/r/root_build > ROOTSYS=/home/rembserj/ ./bin/root Warning in <TROOT>: ROOTSYS is set but inconsistent with detected ROOT installation: ROOTSYS=/home/rembserj/ Detected=/home/rembserj/code/root/root_build ROOT will use the detected installation. ------------------------------------------------------------------ | Welcome to ROOT 6.41.01 https://root.cern | | (c) 1995-2025, The ROOT Team; conception: R. Brun, F. Rademakers | | Built for linuxx8664gcc on Jan 01 1980, 00:00:00 | | From heads/ignoreprefix@v6-99-99-368-gd1d33ba04be | | With clang version 21.1.8 std202002 | | Try '.help'/'.?', '.demo', '.license', '.credits', '.quit'/'.q' | ------------------------------------------------------------------ root [0] ```

guitargeek self-assigned this Jan 25, 2026

guitargeek requested review from bellenot and dpiparo as code owners January 25, 2026 15:04

guitargeek added the in:Build System label Jan 25, 2026

guitargeek requested a review from pcanal as a code owner January 25, 2026 15:04

guitargeek added in:Core Libraries clean build Ask CI to do non-incremental build on PR labels Jan 25, 2026

guitargeek force-pushed the ignoreprefix branch 3 times, most recently from 82f684f to 5bd24d2 Compare January 25, 2026 17:40

guitargeek requested a review from couet as a code owner January 25, 2026 17:40

guitargeek force-pushed the ignoreprefix branch from 5bd24d2 to 99e0747 Compare January 25, 2026 18:14

guitargeek marked this pull request as draft January 26, 2026 08:51

guitargeek force-pushed the ignoreprefix branch 2 times, most recently from 9658e4c to e3a4c50 Compare January 26, 2026 15:54

pcanal reviewed Jan 26, 2026

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Comment thread core/base/src/TSystem.cxx Outdated

guitargeek force-pushed the ignoreprefix branch 6 times, most recently from 301f1a6 to 0c6fb13 Compare January 28, 2026 12:17

guitargeek mentioned this pull request Jan 28, 2026

[tutorials][test] Specify the include path for SOFIE tutorials in CMake #21056

Merged

vepadulano added the build-python-wheels Run the workflow to build Python wheels label Jan 29, 2026

guitargeek mentioned this pull request Jan 29, 2026

[gui] Simplify ROOTSYS handling in TGFSComboBox #21069

Merged

guitargeek force-pushed the ignoreprefix branch from 0c6fb13 to 493acb4 Compare January 30, 2026 07:22

guitargeek mentioned this pull request Jan 30, 2026

[build] Use CMAKE_INSTALL_<dir> variables consistently in setup.py #21075

Merged

guitargeek force-pushed the ignoreprefix branch from c447a98 to 70e57d8 Compare January 30, 2026 09:17

guitargeek force-pushed the ignoreprefix branch from 70e57d8 to 017f67b Compare February 1, 2026 22:23

guitargeek force-pushed the ignoreprefix branch 2 times, most recently from 84ea7d7 to 160e5f1 Compare March 2, 2026 10:52

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guitargeek force-pushed the ignoreprefix branch 5 times, most recently from 489b683 to 6c6dee9 Compare April 26, 2026 20:59

guitargeek marked this pull request as ready for review April 27, 2026 07:49

[ci] Enable gnuinstall in the march=native build

48db120

This is to test that ROOT doesn't get confused at build and test time by the fact that the structure of the install tree and build tree is different, which is the case for `gnuinstall=ON`.

guitargeek force-pushed the ignoreprefix branch from 6c6dee9 to d1d33ba Compare June 18, 2026 11:19

guitargeek requested a review from jblomer as a code owner June 18, 2026 11:19

guitargeek mentioned this pull request Jun 18, 2026

[CI] Test gnuinstall option. #19435

Closed

guitargeek requested a review from pcanal June 18, 2026 11:41

pcanal closed this Jun 18, 2026

pcanal reopened this Jun 18, 2026

pcanal reviewed Jun 18, 2026

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Comment thread core/base/src/TROOT.cxx Outdated

pcanal reviewed Jun 18, 2026

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Comment thread core/base/src/TROOT.cxx Outdated

pcanal reviewed Jun 18, 2026

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guitargeek force-pushed the ignoreprefix branch 2 times, most recently from 16434df to e697135 Compare June 18, 2026 18:49

guitargeek added 2 commits June 19, 2026 00:19

guitargeek force-pushed the ignoreprefix branch from e697135 to 6dde01e Compare June 18, 2026 22:19

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[core] Use automatic build tree detection for all resource directories#21018

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