• Checked for duplicates

Describe the bug

When building root 6.26/04 with gcc 11.2.1 the build process fails while compiling REveBox.cxx:

[ 89%] Building CXX object graf3d/eve7/CMakeFiles/ROOTEve.dir/src/REveBox.cxx.o
In file included from /usr/src/root-6.26.04/graf3d/eve7/src/REveBox.cxx:18:
/usr/include/nlohmann/json.hpp:847:7: error: redeclared with 9 template parameters
847 | class basic_json;
| ^~~~~~~~~~

This is under CentOS 7, using devtoolset-11 and cmake3 (3.17.5).

Expected behavior

It should compile without errors.

To Reproduce

wget https://root.cern/download/root_v6.26.04.source.tar.gz
tar xzvf root_v6.26.04.source.tar.gz
cd root-6.26.04
cd build
scl enable devtoolset-11 bash
cmake3 ..
make >& make.log

Setup

root 6.26.04
CentOS 7, devtoolset-11 (gcc 11.2.1), cmake3 (3.17.5)
Building from source (https://root.cern/download/root_v6.26.04.source.tar.gz)

Additional context