−one This won't response the dilemma while in the title, “When is #include things like library necessary in C++?”. I assume that that would be Alright With all the OP. However it's dilemma when this issue is applied as referent for your close-as-duplicate of some other question. @Oriol thanks https://musiclovers.online/g-eazy-and-halsey-him-and-i-cover-song/