It's that amount of lines UNCOMPILED. Of course uncompiled code wouldn't fit in 64kb of flash (the compiler wouldn't fit either, you know). Compiled, std::optional takes up essentially no overhead, basically the same as if you're returning a single bool along with your object.

> This is practical with an efficient heap allocator (which I might not have). What happens if I want a scoped (on stack) instance of a class?

There is absolutely no reason to do a heap allocation for a factory function in modern C++ (or even relatively ancient C++, in fact). The fact that you would think so indicates you simply don't know C++ at all.

Tell me, where in these six lines do you see a heap allocation? Where in the total of 6 instructions this compiles down to do you see anything that couldn't run in any embedded environment? Tell me how these six instructions wouldn't fit inside your 64kb of flash:

https://godbolt.org/z/rErWPbbbx

And again, EVEN IF you're so religiously and irrationally opposed to using std::optional, you can just return a default-constructed object and an extra bool indicating successful construction. I don't know why you would considering you could just return an optional, but whatever, you can do it that way if that's what you prefer.

You're just wrong about this stuff, and it's this kind of lazy, uniformed criticism of C++ that really rubs me the wrong way. If you wanna use C, use C! Nobody's stopping you, it's a fine language. Just leave the C++ discussions to the people who actually know what the language is.