https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81482
--- Comment #4 from kloetzl <fabian-gcc at kloetzl dot info> --- > And changing the algorithm to make no copies would not make it opaque, because > the lack of copies would be observable. As the standard says, whether copies > are made or not is unspecified. So if you want to treat them as opaque, don't > do something that depends on the internal details, use them as suggested by > the > note in the standard. I see that changing the behaviour might be a bigger issue than the quirks itself. Fixing this on the client side by changing the capture to by-reference is trivial. I just fear that developers might waste quite some working hours trying to figure it out for themselves. Feel free to close this as wontfix/notabug. ☺