Add movable cast support to type casters
This commit allows type_casters to allow their local values to be moved
away, rather than copied, when the type caster instance itself is an rvalue.
This only applies (automatically) to type casters using
PYBIND11_TYPE_CASTER; the generic type type casters don't own their own
pointer, and various value casters (e.g. std::string, std::pair,
arithmetic types) already cast to an rvalue (i.e. they return by value).
This updates various calling code to attempt to get a movable value
whenever the value is itself coming from a type caster about to be
destroyed: for example, when constructing an std::pair or various stl.h
containers. For types that don't support value moving, the cast_op
falls back to an lvalue cast.
There wasn't an obvious place to add the tests, so I added them to
test_copy_move_policies, but also renamed it to drop the _policies as it
now tests more than just policies.
diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
new file mode 100644
index 0000000..d6479c5
--- /dev/null
+++ b/tests/test_copy_move.py
@@ -0,0 +1,100 @@
+import pytest
+from pybind11_tests import has_optional
+
+
+def test_lacking_copy_ctor():
+ from pybind11_tests import lacking_copy_ctor
+ with pytest.raises(RuntimeError) as excinfo:
+ lacking_copy_ctor.get_one()
+ assert "the object is non-copyable!" in str(excinfo.value)
+
+
+def test_lacking_move_ctor():
+ from pybind11_tests import lacking_move_ctor
+ with pytest.raises(RuntimeError) as excinfo:
+ lacking_move_ctor.get_one()
+ assert "the object is neither movable nor copyable!" in str(excinfo.value)
+
+
+def test_move_and_copy_casts():
+ """Cast some values in C++ via custom type casters and count the number of moves/copies."""
+ from pybind11_tests import move_and_copy_casts, move_and_copy_cstats
+
+ cstats = move_and_copy_cstats()
+ c_m, c_mc, c_c = cstats["MoveOnlyInt"], cstats["MoveOrCopyInt"], cstats["CopyOnlyInt"]
+
+ # The type move constructions/assignments below each get incremented: the move assignment comes
+ # from the type_caster load; the move construction happens when extracting that via a cast or
+ # loading into an argument.
+ assert move_and_copy_casts(3) == 18
+ assert c_m.copy_assignments + c_m.copy_constructions == 0
+ assert c_m.move_assignments == 2
+ assert c_m.move_constructions == 2
+ assert c_mc.alive() == 0
+ assert c_mc.copy_assignments + c_mc.copy_constructions == 0
+ assert c_mc.move_assignments == 2
+ assert c_mc.move_constructions == 2
+ assert c_c.alive() == 0
+ assert c_c.copy_assignments == 2
+ assert c_c.copy_constructions == 2
+ assert c_m.alive() + c_mc.alive() + c_c.alive() == 0
+
+
+def test_move_and_copy_loads():
+ """Call some functions that load arguments via custom type casters and count the number of
+ moves/copies."""
+ from pybind11_tests import (move_and_copy_cstats, move_only, move_or_copy, copy_only,
+ move_pair, move_tuple, copy_tuple, move_copy_nested)
+
+ cstats = move_and_copy_cstats()
+ c_m, c_mc, c_c = cstats["MoveOnlyInt"], cstats["MoveOrCopyInt"], cstats["CopyOnlyInt"]
+
+ assert move_only(10) == 10 # 1 move, c_m
+ assert move_or_copy(11) == 11 # 1 move, c_mc
+ assert copy_only(12) == 12 # 1 copy, c_c
+ assert move_pair((13, 14)) == 27 # 1 c_m move, 1 c_mc move
+ assert move_tuple((15, 16, 17)) == 48 # 2 c_m moves, 1 c_mc move
+ assert copy_tuple((18, 19)) == 37 # 2 c_c copies
+ # Direct constructions: 2 c_m moves, 2 c_mc moves, 1 c_c copy
+ # Extra moves/copies when moving pairs/tuples: 3 c_m, 3 c_mc, 2 c_c
+ assert move_copy_nested((1, ((2, 3, (4,)), 5))) == 15
+
+ assert c_m.copy_assignments + c_m.copy_constructions == 0
+ assert c_m.move_assignments == 6
+ assert c_m.move_constructions == 9
+ assert c_mc.copy_assignments + c_mc.copy_constructions == 0
+ assert c_mc.move_assignments == 5
+ assert c_mc.move_constructions == 8
+ assert c_c.copy_assignments == 4
+ assert c_c.copy_constructions == 6
+ assert c_m.alive() + c_mc.alive() + c_c.alive() == 0
+
+
+@pytest.mark.skipif(not has_optional, reason='no <optional>')
+def test_move_and_copy_load_optional():
+ """Tests move/copy loads of std::optional arguments"""
+ from pybind11_tests import (move_and_copy_cstats, move_optional, move_or_copy_optional,
+ copy_optional, move_optional_tuple)
+
+ cstats = move_and_copy_cstats()
+ c_m, c_mc, c_c = cstats["MoveOnlyInt"], cstats["MoveOrCopyInt"], cstats["CopyOnlyInt"]
+
+ # The extra move/copy constructions below come from the std::optional move (which has to move
+ # its arguments):
+ assert move_optional(10) == 10 # c_m: 1 move assign, 2 move construct
+ assert move_or_copy_optional(11) == 11 # c_mc: 1 move assign, 2 move construct
+ assert copy_optional(12) == 12 # c_c: 1 copy assign, 2 copy construct
+ # 1 move assign + move construct moves each of c_m, c_mc, 1 c_c copy
+ # +1 move/copy construct each from moving the tuple
+ # +1 move/copy construct each from moving the optional (which moves the tuple again)
+ assert move_optional_tuple((3, 4, 5)) == 12
+
+ assert c_m.copy_assignments + c_m.copy_constructions == 0
+ assert c_m.move_assignments == 2
+ assert c_m.move_constructions == 5
+ assert c_mc.copy_assignments + c_mc.copy_constructions == 0
+ assert c_mc.move_assignments == 2
+ assert c_mc.move_constructions == 5
+ assert c_c.copy_assignments == 2
+ assert c_c.copy_constructions == 5
+ assert c_m.alive() + c_mc.alive() + c_c.alive() == 0