[boxed]

Yea. And there's even pitfalls the author didn't list. My biggest pet peeve about C++ default arguments it that they are compile time inserted based on the header file. So imagine:

void foo(int a = 1) {}

Now you ship this in a DLL, but realize the default was bad, so you change it to 2 and ship the new DLL. Well, the 1/2 isn't in the DLL at all. It's only in the header file. So everyone must recompile. Fun times.

[bregma]

Technically that's a subtly incompatible ABI change. ABI changes can be notoriously tricky to spot. That's handled properly on an ELF-based system by bumping the SONAME major (if the library developer knows what they're doing) but that won't help non-ELF platforms or vendored uses.

Of course, the same problem applies in other languages if a constant value changes. A preprocessor macros in C, for example. It's all about non-manifest interfaces and "making things easier" so that any idiot can write software (so they do). Public APIs can be hard when the public is imperfect.

[boxed]

> Technically that's a subtly incompatible ABI change

Yea, that's what I said. And it's subtle because of the language making it a foot gun.

> Of course, the same problem applies in other languages if a constant value changes.

That's just C++ the apologist talking.