Is it this?
GCC:
For C++, construction of the global iostream objects std::cout, std::cin, etc. is now done inside the standard library, instead of in every source file that includes the <iostream> header. This change improves the start-up performance of C++ programs, but it means that code compiled with GCC 13.1 will crash if the correct version of libstdc++.so is not used at runtime. See the documentation about using the right libstdc++.so at runtime. Future GCC releases will mitigate the problem so that the program cannot be run at all with an older libstdc++.so.
Or this?
lisbstdc++:
Support for many previously unavailable features in freestanding mode, thanks to Arsen Arsenović. For example, std::tuple is now available for freestanding compilation. The freestanding subset contains all the components made freestanding by P1642, but libstdc++ adds more components to the freestanding subset, such as std::array and std::string_view. Additionally, libstdc++ now respects the -ffreestanding compiler option and so it is not necessary to build a separate freestanding installation of libstdc++. Compiling with -ffreestanding will restrict the available features to the freestanding subset, even if libstdc++ was built as a full, hosted implementation.