When using `method_adaptor` (usually implicitly via a `cl.def("f",
&D::f)`) a compilation failure results if `f` is actually a method of
an inaccessible base class made public via `using`, such as:
class B { public: void f() {} };
class D : private B { public: using B::f; };
pybind deduces `&D::f` as a `B` member function pointer. Since the base
class is inaccessible, the cast in `method_adaptor` from a base class
member function pointer to derived class member function pointer isn't
valid, and a cast failure results.
This was sort of a regression in 2.2, which introduced `method_adaptor`
to do the expected thing when the base class *is* accessible. It wasn't
actually something that *worked* in 2.1, though: you wouldn't get a
compile-time failure, but the method was not callable (because the `D *`
couldn't be cast to a `B *` because of the access restriction). As a
result, you'd simply get a run-time failure if you ever tried to call
the function (this is what #855 fixed).
Thus the change in 2.2 essentially promoted a run-time failure to a
compile-time failure, so isn't really a regression.
This commit simply adds a `static_assert` with an accessible-base-class
check so that, rather than just a cryptic cast failure, you get
something more informative (along with a suggestion for a workaround).
The workaround is to use a lambda, e.g.:
class Derived : private Base {
public:
using Base::f;
};
// In binding code:
//cl.def("f", &Derived::f); // fails: &Derived::f is actually a base
// class member function pointer
cl.def("f", [](Derived &self) { return self.f(); });
This is a bit of a nuissance (especially if there are a bunch of
arguments to forward), but I don't really see another solution.
Fixes#1124
This changes the caster to return a reference to a (new) local `CharT`
type caster member so that binding lvalue-reference char arguments
works (currently it results in a compilation failure).
Fixes#1116
`type_descr` is now applied only to the final signature so that it only
marks the argument types, but not nested types (e.g. for tuples) or
return types.
MSCV does not allow `&typeid(T)` in constexpr contexts, but the string
part of the type signature can still be constexpr. In order to avoid
`typeid` as long as possible, `descr` is modified to collect type
information as template parameters instead of constexpr `typeid`.
The actual `std::type_info` pointers are only collected in the end,
as a `constexpr` (gcc/clang) or regular (MSVC) function call.
Not only does it significantly reduce binary size on MSVC, gcc/clang
benefit a little bit as well, since they can skip some intermediate
`std::type_info*` arrays.
The current C++14 constexpr signatures don't require relaxed constexpr,
but only `auto` return type deduction. To get around this in C++11,
the type caster's `name()` static member functions are turned into
`static constexpr auto` variables.
E.g. trying to convert a `list` to a `std::vector<int>` without
including <pybind11/stl.h> will now raise an error with a note that
suggests checking the headers.
The note is only appended if `std::` is found in the function
signature. This should only be the case when a header is missing.
E.g. when stl.h is included, the signature would contain `List[int]`
instead of `std::vector<int>` while using stl_bind.h would produce
something like `MyVector`. Similarly for `std::map`/`Dict`, `complex`,
`std::function`/`Callable`, etc.
There's a possibility for false positives, but it's pretty low.
To avoid an ODR violation in the test suite while testing
both `stl.h` and `std_bind.h` with `std::vector<bool>`,
the `py::bind_vector<std::vector<bool>>` test is moved to
the secondary module (which does not include `stl.h`).
There are two separate additions:
1. `py::hash(obj)` is equivalent to the Python `hash(obj)`.
2. `.def(hash(py::self))` registers the hash function defined by
`std::hash<T>` as the Python hash function.
The lookup of the `self` type and value pointer are moved out of
template code and into `dispatcher`. This brings down the binary
size of constructors back to the level of the old placement-new
approach. (It also avoids a second lookup for `init_instance`.)
With this implementation, mixing old- and new-style constructors
in the same overload set may result in some runtime overhead for
temporary allocations/deallocations, but this should be fine as
old style constructors are phased out.
Creating an instance of of a pybind11-bound type caused a reference leak in the
associated Python type object, which could prevent these from being collected
upon interpreter shutdown. This commit fixes that issue for all types that are
defined in a scope (e.g. a module). Unscoped anonymous types (e.g. custom
iterator types) always retain a positive reference count to prevent their
collection.
The current PYBIND11_INTERNALS_ID depends on the version of the library
in order to isolate binary incompatible internals capsules. However,
this does not preclude conflicts between modules built from different
(binary incompatible) commits with the same version number.
For example, if one module was built with an early v2.2.dev and
submitted to PyPI, it could not be loaded alongside a v2.2.x release
module -- it would segfault because of incompatible internals with
the same ID.
This PR changes the ID to depend on PYBIND11_INTERNALS_VERSION which is
independent of the main library version. It's an integer which should be
incremented whenever a binary incompatible change is made to internals.
PYBIND11_INTERNALS_KIND is also introduced for a similar reason.
The same versioning scheme is also applied to `type_info` and the
`module_local` type attribute.
The "see above" comment being referenced in the code comments isn't
"above" anymore; copy the later factory init comment into the first
constructor block to fix it.
The main point of `py::module_local` is to make the C++ -> Python cast
unique so that returning/casting a C++ instance is well-defined.
Unfortunately it also makes loading unique, but this isn't particularly
desirable: when an instance contains `Type` instance there's no reason
it shouldn't be possible to pass that instance to a bound function
taking a `Type` parameter, even if that function is in another module.
This commit solves the issue by allowing foreign module (and global)
type loaders have a chance to load the value if the local module loader
fails. The implementation here does this by storing a module-local
loading function in a capsule in the python type, which we can then call
if the local (and possibly global, if the local type is masking a global
type) version doesn't work.
This reimplements the py::init<...> implementations using the various
functions added to support `py::init(...)`, and moves the implementing
structs into `detail/init.h` from `pybind11.h`. It doesn't simply use a
factory directly, as this is a very common case and implementation
without an extra lambda call is a small but useful optimization.
This, combined with the previous lazy initialization, also avoids
needing placement new for `py::init<...>()` construction: such
construction now occurs via an ordinary `new Type(...)`.
A consequence of this is that it also fixes a potential bug when using
multiple inheritance from Python: it was very easy to write classes
that double-initialize an existing instance which had the potential to
leak for non-pod classes. With the new implementation, an attempt to
call `__init__` on an already-initialized object is now ignored. (This
was already done in the previous commit for factory constructors).
This change exposed a few warnings (fixed here) from deleting a pointer
to a base class with virtual functions but without a virtual destructor.
These look like legitimate warnings that we shouldn't suppress; this
adds virtual destructors to the appropriate classes.
This allows you to use:
cls.def(py::init(&factory_function));
where `factory_function` returns a pointer, holder, or value of the
class type (or a derived type). Various compile-time checks
(static_asserts) are performed to ensure the function is valid, and
various run-time type checks where necessary.
Some other details of this feature:
- The `py::init` name doesn't conflict with the templated no-argument
`py::init<...>()`, but keeps the naming consistent: the existing
templated, no-argument one wraps constructors, the no-template,
function-argument one wraps factory functions.
- If returning a CppClass (whether by value or pointer) when an CppAlias
is required (i.e. python-side inheritance and a declared alias), a
dynamic_cast to the alias is attempted (for the pointer version); if
it fails, or if returned by value, an Alias(Class &&) constructor
is invoked. If this constructor doesn't exist, a runtime error occurs.
- for holder returns when an alias is required, we try a dynamic_cast of
the wrapped pointer to the alias to see if it is already an alias
instance; if it isn't, we raise an error.
- `py::init(class_factory, alias_factory)` is also available that takes
two factories: the first is called when an alias is not needed, the
second when it is.
- Reimplement factory instance clearing. The previous implementation
failed under python-side multiple inheritance: *each* inherited
type's factory init would clear the instance instead of only setting
its own type value. The new implementation here clears just the
relevant value pointer.
- dealloc is updated to explicitly set the leftover value pointer to
nullptr and the `holder_constructed` flag to false so that it can be
used to clear preallocated value without needing to rebuild the
instance internals data.
- Added various tests to test out new allocation/deallocation code.
- With preallocation now done lazily, init factory holders can
completely avoid the extra overhead of needing an extra
allocation/deallocation.
- Updated documentation to make factory constructors the default
advanced constructor style.
- If an `__init__` is called a second time, we have two choices: we can
throw away the first instance, replacing it with the second; or we can
ignore the second call. The latter is slightly easier, so do that.
An alias can be used for two main purposes: to override virtual methods,
and to add some extra data to a class needed for the pybind-wrapper.
Both of these absolutely require that the wrapped class be polymorphic
so that virtual dispatch and destruction, respectively, works.
`function_signature_t` extracts the function type from a function,
function pointer, or lambda.
`is_lambda` (which is really
`is_not_a_function_or_pointer_or_member_pointer`, but that name is a
bit too long) checks whether the type is (in the approprate context) a
lambda.
`is_function_pointer` checks whether the type is a pointer to a
function.
We currently allocate instance values when creating the instance itself
(except when constructing the instance for a `cast()`), but there is no
particular reason to do so: the instance itself and the internals (for
a non-simple layout) are allocated via Python, with no reason to
expect better locality from the invoked `operator new`. Moreover, it
makes implementation of factory function constructors trickier and
slightly less efficient: they don't use the pre-eallocate the memory,
which means there is a pointless allocation and free.
This commit makes the allocation lazy: instead of preallocating when
creating the instance, the allocation happens when the instance is
first loaded (if null at that time).
In addition to making it more efficient to deal with cases that don't
need preallocation, this also allows for a very slight performance
increase by not needing to look up the instances types during
allocation. (There is a lookup during the eventual load, of course, but
that is happening already).
This adds a PYBIND11_NAMESPACE macro that expands to the `pybind11`
namespace with hidden visibility under gcc-type compilers, and otherwise
to the plain `pybind11`. This then forces hidden visibility on
everything in pybind, solving the visibility issues discussed at end
end of #949.
In C++11 mode, `boost::apply_visitor` requires an explicit `result_type`.
This also adds optional tests for `boost::variant` in C++11/14, if boost
is available. In C++17 mode, `std::variant` is tested instead.
