Root with C++17 support

[jkerdels]

Hi,

I wanted to compile root with support for c++17. I read this (already closed) post:

Root compatibility with c++17

Hey there! I was wondering if there is a root precompiled library that was built using gcc 7.1.0. My current root version was compiled using gcc 5.3.0, and it seems to fail when I’m running a modern compiler with std=c++1z flag. It seems to be all right with std=c++1y though. Compiler version: gcc (GCC) 7.1.0 Compiler flags: -std=c++1z -O3 -Wall -fPIC -pthread -m64 -I/cvmfs/cms.cern.ch/slc6_amd64_gcc530/cms/cmssw/CMSSW_9_1_0_pre3/external/slc6_amd64_gcc530/bin/…/…/…/…/…/…/…/slc6_amd64_gcc53…

If I use cmake-gui on a freshly cloned root source (using tag v6-11-02) I do not find the advertised option cxx17. If I add it manually, the build fails as described in the post linked above. I also tried to use the master branch, but it failed as well.

Any Ideas?

Cheers,
Jochen

[bellenot]

Hi,

I think it is not ready yet

Cheers, Bertrand.

[jkerdels]

Hi Bertrand,

ah, ok. :-/

Eagerly waiting for c++17

Cheers,
Jochen

PS: Is there an approximate ETA for the c++17 support?

[amadio]

Hi @jkerdels,

ROOT is not yet ready for C++17, unfortunately. However, ROOT 6.12 will be released soon, and that version will support C++17. Currently, there are bugs (in GCC) that prevent building with GCC-7.2.0 in C++17 mode, but I have a branch where I can successfully build with Clang-5.0 in C++17 mode. I will soon make a PR with the changes in that branch, so hopefully before the end of this week the master branch will support C++17 out of the box. Cheers,

[jkerdels]

That is great news! Thanks for the quick and informative response!