Performed en-masse via: $ grep -rn "#include <ll" libc/include -l | \ xargs perl -pi -e 's/#include <ll(.*)>/#include "ll$1"/' $ grep -rn "#include <__" libc/include -l | \ xargs perl -pi -e 's/#include <__(.*)>/#include "__$1"/' Link: #83463 Link: #83210
We expect to eventually provide a complete implementation, but having an empty definition is necessary to unblock the use of libc++ in embedded environments. See #84884 for more details.