Of course I know about the POD idiom. You and chipdart are misunderstanding me because there's a tension between how the C++ Standard defines things and how C++ gets used in real life. Because strictly speaking, the Standard doesn't really have a concept of POD[0]. What it does have is "trivial" classes and the concept of object lifetime. For instance, if your class/struct isn't trivially_copyable and you memcpy it like a C struct, you're in Undefined Behavior country. If your class/struct is such that you must observe C++'s lifetime rules, but you are writing its fields by casting a char pointer to some bytes, that's UB.

But yes, if you make extra sure (under threat of footgun) that your struct only has simple types in it and doesn't use virtual or define any ctors/dtors or use protected/private or use inheritance and all of its members follow those rules etc etc, maybe you can treat it like a C struct. But the C++ Standard is telling a different story.

Keep in mind, I'm not blaming you for ignoring all these complications if at the end of the day the compiler seems to give you the behavior you expect. But the fun of C++ is that it's kind of two programming languages in one: the language the Standard defines, and the language the typical programmer thinks it is.

[0] There was std::is_pod, but it was deprecated because it doesn't reflect how the Standard actually defines things. A bit of a cruel joke, dangling that in front of us and then yanking it away.