fix R3BRoot/r3bbase/R3BFileSource2.h:29:48: error: no template named …

[audreychatillon]

…'optional' in namespace 'std'

fix error: invalid use of incomplete type ‘class std::basic_ostream’

Describe your proposal.

Mention any issue this PR is resolved or is related to.

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Checklist:

• Rebased against dev branch
• My name is in the resp. CONTRIBUTORS/AUTHORS file
• Followed the pull request guidlines and the Git workflow
• Followed the seven rules of great commit messages

[YanzhaoW]

Thanks a lot for the PR. This problem comes from my PR #910 and I had no idea why it compiled successfully both in the CI and lxir136 machine.

But I did see it when I tried to compile R3BRoot using gcc12.

Which gcc version do you use when you found this issue?

Also please create another PR based on dev branch and as it's a small change, we could merge it quickly as well. @jose-luis-rs

[audreychatillon]

gcc --version
gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0

[YanzhaoW]

Yeah, that makes sense. In our CI, gcc version is 8.3.0 and probably gcc 8 includes some headers by default and somehow they are not included anymore in newer versions.