Boost C++ Libraries: Ticket #11904: is_nothrow_move_constructible does not compile on GCC 4.6

John Maddock — Tue, 12 Jan 2016 18:00:03 GMT

I don't know how to fix this - those GCC versions fail inside the noexcept expression when the class being tested has a private assignment operator or copy constructor. There appear to be no compiler intrinsics available for those GCC versions either. So I'm stuck.

BTW I don't believe this ever worked, but I could be wrong?

akrzemi1 — Tue, 12 Jan 2016 18:58:49 GMT

Replying to johnmaddock:

I don't know how to fix this - those GCC versions fail inside the noexcept expression when the class being tested has a private assignment operator or copy constructor. There appear to be no compiler intrinsics available for those GCC versions either. So I'm stuck.

I understand the difficulty. Is it possible to isolate the offending compiler versions and provide a trivial definition of the trait for them? I can see it is not easy as the traits seam to work for other testers with GCC 4.6.

BTW I don't believe this ever worked, but I could be wrong?

I cannot be sure. But I thing these errors weren't there in Boost.Optional. Perhaps these testers are new.

status changed; resolution set

John Maddock — Wed, 13 Jan 2016 11:59:41 GMT

status new → closed
resolution → fixed

OK, I've basically disabled these two traits for older gcc versions - see https://github.com/boostorg/type_traits/commit/1f3a3a1553dc316ed002354dce3ba3f081b2e102 - note that this introduces new failures as all UDT's now report false with these traits for gcc < 4.8, this is safe but obviously sub-optimal.

John Maddock — Wed, 07 Mar 2018 19:06:18 GMT

Update: in response to https://github.com/boostorg/variant/issues/47 I've tentatively re-enabled support for is_nothrow_move_constructible in gcc-4.7. Tests all pass locally, so we'll see.