[Const-me]

> If your code is slower than C, someone will rewrite it in C.

When used correctly, C++ is not slower than C. Sometimes faster, a classic example is C qsort versus std::sort.

> If your library is written in C it means it can be used on any OS, console or mobile device and even on the web.

C++ is good in that regard. I know only 1 mainstream platform where C++ adds significant friction compared to C, that’s iOS, because their objective C is a superset of C. The rest of them (Windows, Linux including embedded, game consoles, android) support C++ just fine.

> Not everyone wants to use C++ (some prefer C).

Most people are OK with C++, especially in the context of game development.

> to the point where you are pretty much left with C

No, not with C. Namespaces and scoped enums are awesome.

Another thing, inside the implementation of the library, you can use whatever C++ language features you please, even the features that would be inappropriate when exposed at the API surface of the library. For example, MS implemented parts of their C runtime library with C++ classes, RAII, lambdas and templates, eliminating duplicated code for char/wchar_t routines. Obviously, you don’t need C++ to consume that library, just C is enough, but it’s implemented in modern C++. On my system, that source is in "C:\Program Files (x86)\Windows Kits\10\Source\10.0.18362.0\ucrt\stdio\output.cpp".

[comex]

> I know only 1 mainstream platform where C++ adds significant friction compared to C, that’s iOS, because their objective C is a superset of C.

Apple’s compiler supports overlaying Objective-C features on top of C++ instead of C; it’s called Objective-C++.

[Const-me]

I once forked a C library, porting some parts to C++ in the process: https://github.com/Const-me/nanovg/ I’ve retained original C API, only used C++ in the implementation.

Then I’ve got an e-mail from a developer who asked a few things how to back port my changes to C. I answered their questions, but I was curious why. They replied it’s because Objective C and iOS. Personally, I haven’t been developing for iOS for several years, but I don’t think people would do such things for lulz.

[oriolid]

That developer must be misinformed. I have been developing a native component that needs to interface with C++ APIs from the app and Objective C APIs from iOS. The only thing you need to remember is to not mix exceptions from C++ and Objective C. The object models are also incompatible, but the compiler prevents you from mixing them.

[comex]

Also, if C++ is only used in the library implementation... you wouldn't even need Objective-C++ unless you needed to add Objective-C API calls to the library's own source files. Otherwise, you could just compile the library's source files as regular C++, and link them together with your Objective-C code. This works exactly the same way as combining C and C++, and Xcode (the IDE) has no issue with it. So it seems very likely that the developer was misinformed.

[pjmlp]

Except that only old timers, have the Objective-C++ documentation available, because Apple has removed it from their web site.