Well yeah. If you make normal, idiomatic use of include guards, compilers will be able to apply this optimization. If you do weird stuff, they'll be forced to

Well yeah. If you make normal, idiomatic use of include guards, compilers will be able to apply this optimization. If you do weird stuff, they'll be forced to re-read the file. https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html https://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.htm...