[tialaramex]

Lots of the C++ standard library, including the STL containers isn't provided in freestanding C++. Now, in reality freestanding C++ has been kind of a joke - the committee for years barely bothered to keep it working - especially compared to freestanding C (which is well defined and used all over the place) and say Rust no_std (likewise) - and so many embedded systems may have the entire standard library notionally available even though parts of it are definitely nonsense for them and they've got local rules saying not to use the parts that would definitely explode in their environment... but many C++ programmers who have worked under such rules just reflexively avoid the STL's containers and maybe its algorithms even in an environment where those would work.