Hacker News new | past | comments | ask | show | jobs | submit
RyanJK5 | on: Beautiful Type Erasure with C++26 Reflection
Try it on Compiler Explorer: https://godbolt.org/z/91dj5jeGW

Check out the source code: https://github.com/RyanJK5/rjk-duck

gmueckl | parent | next
An include with a HTTP URL is a scary abomination straight put of hell. Please tell me that this is a compiler explorer specialty (which would still be cursed, but in a cool way) and not a GCC feature (which would be an absolute nightmare).
aw1621107 | root | parent
Yes, it's a Compiler Explorer feature. URL includes get rewritten client-side to work as if they were additional files supplied by the user. PR adding the current behavior is at [0], while I think the downloading code itself is at [1].

[0]: https://github.com/compiler-explorer/compiler-explorer/pull/...

[1]: https://github.com/compiler-explorer/compiler-explorer/blob/...

schaefer | parent
in the first example:

```

10: rjk::duck<Container> c{std::vector<int>{1, 2, 3}};

11: c.size(); // 3

12:

13: c = std::string{"hello"};

```

Does the assignment on line 13 call the destrucor for the vector of ints created on line 10?

RyanJK5 | root | parent | next
Yes. duck takes ownership of the vector by moving it into its internal storage.

As a bonus, if you tried passing in an lvalue, it will reject the input unless you add the "copyable" trait, so it ends up mitigating some hidden copies.

schaefer | root | parent
Well, you’ve certainly convinced me to read your library.

Thanks for the blog post.

RyanJK5 | root | parent
No problem! Hope you enjoy :)
rycomb | root | parent
Is there another option? Or were you asking if it leaks memory?

Maybe you were asking if it implements custom destructors? GC?

schaefer | root | parent
> Or were you asking if it leaks memory?

yeah,

If variable c where of type void* instead of duck<Container>, the assignment on line 13 would leak the memory used by the vector<int>.