Creating a default executable C/C++ project and simply using the following main code causes the following error: "cannot combine with previous 'int' declaration specifier" C Source Code (5 lines)
The absolute best option would be if segger distributed the full STL as provided by the ARM toolchain, but the minimum conforming freestanding environment would at least be a start.
Some headers required by C++ freestanding implementations that are really really useful are missing, like atomic and type_traits (among others). It would be great if Segger could provide at least the headers required by C++11 freestanding, see en.cppreference.com/w/cpp/freestanding for a list.