[cmake] move ExternalProject_Add to subdir for consistency, and define proper GSL,FFTW,TBB targets

[ferdymercury]

Try unbloating the huge SearchInstalledSoftware
and use always subdirs for ExternalProject_Add for symmetry with other builtins

[github-actions]

Test Results

    15 files      15 suites   2d 2h 6m 13s ⏱️
 3 808 tests  3 807 ✅ 0 💤 1 ❌
51 104 runs  51 103 ✅ 0 💤 1 ❌

For more details on these failures, see this check.

Results for commit 070cca6.

♻️ This comment has been updated with latest results.

[ferdymercury]

@bellenot could you let me know what is the contents (filenames) inside:

C:/libs/x64/fftw/3.3.5/lib on the Windows runners?

Or alternatively, what targets are defined once you run find_package with the new FindFFTW.cmake script in this branch ?

[bellenot]

@ferdymercury here is the content of C:\libs\x64\fftw\3.3.5\lib:

 Directory of C:\libs\x64\fftw\3.3.5\lib

10/11/2025  13:17    <DIR>          .
10/11/2025  13:17    <DIR>          ..
04/03/2022  11:47           238,966 fftw3-3.lib
03/03/2022  09:13           241,990 libfftw3-3.lib
03/03/2022  09:13           247,600 libfftw3f-3.lib
03/03/2022  09:13           149,230 libfftw3l-3.lib
               4 File(s)        877,786 bytes
               2 Dir(s)  73,924,689,920 bytes free

And I'll try your branch...

[bellenot]

@ferdymercury BTW, what is the problem with FFTW?

[bellenot]

And here is what CMake finds:

[bellenot]

Here are (some of) the errors on Windows:

[...]
    Exit code 0xc0000135
    Exit code 0xc0000135
    Exit code 0xc0000135
  C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppCommon.targets(254,5): error MSB8066: Custom build for 'C:\ROOT-CI\build\CMakeFiles\d062ca236c6013e32d1af865d69dc514\G__RooFitJSONInterface.cxx.rule;C:\ROOT-CI\src\roofit\jsoninterface\CMakeLists.txt' exited with code 1. [C:\ROOT-CI\build\roofit\jsoninterface\G__RooFitJSONInterface.vcxproj]
    Generating G__ROOTGpadv7.cxx, ../../bin/libROOTGpadv7_rdict.pcm, ../../bin/libROOTGpadv7.rootmap
  C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppCommon.targets(254,5): error MSB8066: Custom build for 'C:\ROOT-CI\build\CMakeFiles\9c31611484f5c242b181395c24233222\DataFrameSnapshotUtils.cxx.rule;C:\ROOT-CI\src\tree\dataframe\test\CMakeLists.txt' exited with code 1. [C:\ROOT-CI\build\tree\dataframe\test\DataFrameSnapshotUtils.vcxproj]
    Generating RXTupleDict.cxx, libntuple_compat_rdict.pcm, libntuple_compat.rootmap
  C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Microsoft\VC\v180\Microsoft.CppCommon.targets(254,5): error MSB8066: Custom build for 'C:\ROOT-CI\build\CMakeFiles\4216675670bde90fccb32452aa24052b\G__XMLParser.cxx.rule;C:\ROOT-CI\src\io\xmlparser\CMakeLists.txt' exited with code 1. [C:\ROOT-CI\build\io\xmlparser\G__XMLParser.vcxproj]
    Exit code 0xc0000135
    Exit code 0xc0000135
[...]

Hard to tell where they are coming from (i.e, which DLL is not found). I'll have to debug it locally

[ferdymercury]

what is the problem with FFTW?

The current FindFFTW.cmake did not define a proper target so I borrowed a more up-to-date one by @egpbos but it seems it had a bug for Win32. I just fixed it so that it now finds all variants of FFTW3 correctly on Windows.

[bellenot]

@ferdymercury FYI the issue is coming from TBB. I'm looking into it

[hageboeck]

This is a good opportunity to make the builtins conform to what find modules would output. This means that we need to set the following variables (from here):

Xxx_INCLUDE_DIRS
Xxx_LIBRARIES

We also need to remember that:

• They must not be CACHE variables
• And they need to be set in the PARENT_SCOPE now that they are in subdirectories

I see that for some deps, this is done, for others it's not, so we have a chance now to unify this.

[hageboeck]

This needs to be set also in the PARENT_SCOPE when it's moved into a subdirectory.

[hageboeck]

You need to set FFTW_INCLUDE_DIRS in the parent scope.