[Bug libstdc++/48038] [C++0x] stable_sort problem with C++0x and comparator by value

["chris at bubblescope dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48038

--- Comment #18 from Chris Jefferson <chris at bubblescope dot net> 2011-03-09 13:34:51 UTC ---
Just to update:

I have checked other users of MOVE_ITERATOR (there are only two) and they
appear fine, as they do not use a comparator.

Attached is an initial patch. Very sorry if the formatting (particular tabs)
are off, I am using a different texteditor to normal and am having trouble
configuring correctly.

This patch might look quite long but it is actually fairly minimal.

Basically we introduce methods __move_merge_backward and __move_merge, which
act similarly to merge but move values. We call the comparitor methods without
any moving, so they behave themselves.

__merge_backward was only ever used with arguments that move, so I have renamed
it to __move_merge_backward for clarity and changed the places it is called.
Also introduce __move_merge which is identical to std::merge, except it moves
values into place rather than copies them.

Then fix all places which call merge or __merge_backward with MOVE_ITERATORS to
use the new methods.

Finally, there is a little testcase.


As a sanity check, I would like to make sure that other types (the other sorts
being the obvious target) also work correctly. I can't imagine why they
wouldn't, but I'm very suprised this broke!