I don't know. Bjarne's has been saying for 40 years that C++ will eventually have opt-in garbage collectors written for it, but after all this time I don't think one exists yet unless you count C++/CLI.

For example, the 1987 edition of "The C++ Programming Language" (only 328 pages, including the index!) explains how the user can handle `new` failures with `set_new_handler` to "plug in" a garbage collection function that frees up memory and handles the failure.

And section 10.7 of "The Design and Evolution of C++", is titled "Automatic Garbage Collection", and covers in depth his reasons for not including a garbage collector, and explains a bit about how a plugin automatic collector might work. The TL;DR is that the hardware of the time was too limited and the performance overhead would have killed C++'s chances in its target market. He also posits that memory leaks "are quite acceptable" in many applications because most don't have to run forever and aren't "foundation libraries', but he's probably changed his mind on that by now.