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Fix wrapper's 'value' and 'owned' if ctor missing

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type_caster_generic::cast(): The values of

    wrapper->value
    wrapper->owned

are incorrect in the case that a return value policy of 'copy' is
requested but there is no copy-constructor.  (Similarly 'move'.)  In
particular, if the source object is a static instance, the destructor of
the 'object' 'inst' leads to class_::dealloc() which incorrectly
attempts to 'delete' the static instance.

This commit re-arranges the code to be clearer as to what the values of
'value' and 'owned' should be in the various cases.  Behaviour is
different to previous code only in two situations:

policy = copy but no copy-ctor: Old code leaves 'value = src, owned =
true', which leads to trouble.  New code leaves 'value = nullptr, owned
= false', which is correct.

policy = move but no move- or copy-ctor: old code leaves 'value = src,
owned = true', which leads to trouble.  New code leaves 'value =
nullptr, owned = false', which is correct.
This commit is contained in:
Ben North 2016-10-20 21:09:25 +01:00
parent 77898af0f8
commit 24a2054dbc
1 changed files with 31 additions and 14 deletions
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41
include/pybind11/cast.h
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@ -258,31 +258,48 @@ public:
auto wrapper = (instance<void> *) inst.ptr();
wrapper->value = nullptr;
wrapper->owned = false;
switch (policy) {
case return_value_policy::automatic:
case return_value_policy::take_ownership:
wrapper->value = src;
wrapper->owned = true;
break;
if (policy == return_value_policy::automatic)
policy = return_value_policy::take_ownership;
else if (policy == return_value_policy::automatic_reference)
policy = return_value_policy::reference;
case return_value_policy::automatic_reference:
case return_value_policy::reference:
wrapper->value = src;
wrapper->owned = false;
break;
if (policy == return_value_policy::copy) {
case return_value_policy::copy:
if (copy_constructor)
wrapper->value = copy_constructor(wrapper->value);
wrapper->value = copy_constructor(src);
else
throw cast_error("return_value_policy = copy, but the object is non-copyable!");
} else if (policy == return_value_policy::move) {
wrapper->owned = true;
break;
case return_value_policy::move:
if (move_constructor)
wrapper->value = move_constructor(wrapper->value);
wrapper->value = move_constructor(src);
else if (copy_constructor)
wrapper->value = copy_constructor(wrapper->value);
wrapper->value = copy_constructor(src);
else
throw cast_error("return_value_policy = move, but the object is neither movable nor copyable!");
} else if (policy == return_value_policy::reference) {
wrapper->owned = false;
} else if (policy == return_value_policy::reference_internal) {
wrapper->owned = true;
break;
case return_value_policy::reference_internal:
wrapper->value = src;
wrapper->owned = false;
detail::keep_alive_impl(inst, parent);
break;
default:
throw cast_error("unhandled return_value_policy: should not happen!");
}
tinfo->init_holder(inst.ptr(), existing_holder);