Are you talking about #include being differently handled by the pre-processor than #pragma? And/or about different preprocessing phases and handling of macro expansion? You are using #include once inside a condition, is this on purpose for showing some difference to #pragma once? -----Ursprüngliche Nachricht----- Von:Muhammad via Std-Proposals <std-proposals_at_[hidden]> Gesendet:So 23.03.2025 07:34 Betreff:Re: [std-proposals] #pragma once safer alternative An:std-proposals_at_[hidden]; CC:Muhammad <mail_at_[hidden]>; OK, let's revisit #include for a minute. When the compiler hit the #include directive it will add the content of that file in-place of that directive and then will recursively scan the content for other #include for expansion.