This is the mail archive of the libstdc++@gcc.gnu.org mailing list for the libstdc++ project.
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |
Other format: | [Raw text] |
On 10 October 2016 at 21:19, Jonathan Wakely <jwakely@redhat.com> wrote: > I prefer to put "explicit" on a line of its own, as we do for return > types, but I won't complain if you leave it like this. Changed. >> + any(__rhs).swap(*this); > > > I was trying to avoid the "redundant" xfer operations that the swap > does, but I don't think we can do that and be exception safe. This is > simple and safe, and I think its optimal. Thanks. Right, as discussed, this is now just a move assignment from a temporary. > >> } >> return *this; >> } >> @@ -232,7 +228,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> else if (this != &__rhs) >> { >> if (has_value()) >> - _M_manager(_Op_destroy, this, nullptr); >> + reset(); > > > If you're going to use reset() then you don't need the has_value() > check first. I think the reason I didn't use reset() was to avoid the I removed the check, works fine. > dead store to _M_manager that reset() does, since the compiler might > not detect it's dead (because the next store is done by the call > through a function pointer). > This code was all pretty carefully written to avoid any redundant > operations. Does this change buy us anything except simpler code? As discussed, destroying the value but leaving the manager non-null will do bad things. New patch attached, ok for trunk? 2016-10-10 Ville Voutilainen <ville.voutilainen@gmail.com> Make any's copy assignment operator exception-safe, don't copy the underlying value when any is moved, make in_place constructors explicit. * include/std/any (any(in_place_type_t<_ValueType>, _Args&&...)): Make explicit. (any(in_place_type_t<_ValueType>, initializer_list<_Up>, _Args&&...)): Likewise. (operator=(const any&)): Make strongly exception-safe. (operator=(any&&)): reset() unconditionally in the case where rhs has a value. (operator=(_ValueType&&)): Indent the return type. (_Manager_internal<_Tp>::_S_manage): Move in _Op_xfer, don't copy. * testsuite/20_util/any/assign/2.cc: Adjust. * testsuite/20_util/any/assign/exception.cc: New. * testsuite/20_util/any/cons/2.cc: Adjust. * testsuite/20_util/any/cons/explicit.cc: New. * testsuite/20_util/any/misc/any_cast_neg.cc: Ajust.
Attachment:
any-fixes_2.diff
Description: Text document
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |