Found the following significant warnings:
  /usr/lib/gcc/x86_64-linux-gnu/15/../../../../include/c++/15/ciso646:49:6: warning: "<ciso646> is not a standard header since C++20, use <version> to detect implementation-specific macros" [-W#warnings]
See ‘/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/symengine.Rcheck/00install.out’ for details.
* used C++ compiler: ‘Debian clang version 21.1.8 (3+b1)’
Found the following significant warnings:
  /usr/include/c++/15/ciso646:49:6: warning: #warning "<ciso646> is not a standard header since C++20, use <version> to detect implementation-specific macros" [-Wcpp]
See ‘/home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/symengine.Rcheck/00install.out’ for details.
* used C++ compiler: ‘g++-15 (Debian 15.2.0-13) 15.2.0’
Found the following significant warnings:
  /usr/include/c++/15/ciso646:49:6: warning: #warning "<ciso646> is not a standard header since C++20, use <version> to detect implementation-specific macros" [-Wcpp]
See ‘/data/gannet/ripley/R/packages/tests-devel/symengine.Rcheck/00install.out’ for details.
* used C++ compiler: ‘g++ (GCC) 15.1.1 20250521 (Red Hat 15.1.1-2)’
installed size is 45.5Mb
  sub-directories of 1Mb or more:
    libs  44.9Mb
GNU make is a SystemRequirements.
installed size is 44.6Mb
  sub-directories of 1Mb or more:
    libs  44.0Mb
GNU make is a SystemRequirements.
installed size is  5.2Mb
  sub-directories of 1Mb or more:
    libs   4.6Mb