diff --git a/docs/advanced/exceptions.rst b/docs/advanced/exceptions.rst index f70c202fd..738fb0ba9 100644 --- a/docs/advanced/exceptions.rst +++ b/docs/advanced/exceptions.rst @@ -75,9 +75,10 @@ Registering custom translators If the default exception conversion policy described above is insufficient, pybind11 also provides support for registering custom exception translators. -To register a simple exception conversion that translates a C++ exception into -a new Python exception using the C++ exception's ``what()`` method, a helper -function is available: +Similar to pybind11 classes, exception translators can be local to the module +they are defined in or global to the entire python session. To register a simple +exception conversion that translates a C++ exception into a new Python exception +using the C++ exception's ``what()`` method, a helper function is available: .. code-block:: cpp @@ -87,12 +88,20 @@ This call creates a Python exception class with the name ``PyExp`` in the given module and automatically converts any encountered exceptions of type ``CppExp`` into Python exceptions of type ``PyExp``. +A matching function is available for registering a local exception translator: + +.. code-block:: cpp + + py::register_local_exception(module, "PyExp"); + + It is possible to specify base class for the exception using the third parameter, a `handle`: .. code-block:: cpp py::register_exception(module, "PyExp", PyExc_RuntimeError); + py::register_local_exception(module, "PyExp", PyExc_RuntimeError); Then `PyExp` can be caught both as `PyExp` and `RuntimeError`. @@ -100,16 +109,18 @@ The class objects of the built-in Python exceptions are listed in the Python documentation on `Standard Exceptions `_. The default base class is `PyExc_Exception`. -When more advanced exception translation is needed, the function -``py::register_exception_translator(translator)`` can be used to register +When more advanced exception translation is needed, the functions +``py::register_exception_translator(translator)`` and +``py::register_local_exception_translator(translator)`` can be used to register functions that can translate arbitrary exception types (and which may include -additional logic to do so). The function takes a stateless callable (e.g. a +additional logic to do so). The functions takes a stateless callable (e.g. a function pointer or a lambda function without captured variables) with the call signature ``void(std::exception_ptr)``. When a C++ exception is thrown, the registered exception translators are tried in reverse order of registration (i.e. the last registered translator gets the -first shot at handling the exception). +first shot at handling the exception). All local translators will be tried +before a global translator is tried. Inside the translator, ``std::rethrow_exception`` should be used within a try block to re-throw the exception. One or more catch clauses to catch @@ -168,6 +179,53 @@ section. with ``-fvisibility=hidden``. Therefore exceptions that are used across ABI boundaries need to be explicitly exported, as exercised in ``tests/test_exceptions.h``. See also: "Problems with C++ exceptions" under `GCC Wiki `_. + +Local vs Global Exception Translators +===================================== + +When a global exception translator is registered, it will be applied across all +modules in the reverse order of registration. This can create behavior where the +order of module import influences how exceptions are translated. + +If module1 has the following translator: + +.. code-block:: cpp + + py::register_exception_translator([](std::exception_ptr p) { + try { + if (p) std::rethrow_exception(p); + } catch (const std::invalid_argument &e) { + PyErr_SetString("module1 handled this") + } + } + +and module2 has the following similar translator: + +.. code-block:: cpp + + py::register_exception_translator([](std::exception_ptr p) { + try { + if (p) std::rethrow_exception(p); + } catch (const std::invalid_argument &e) { + PyErr_SetString("module2 handled this") + } + } + +then which translator handles the invalid_argument will be determined by the +order that module1 and module2 are imported. Since exception translators are +applied in the reverse order of registration, which ever module was imported +last will "win" and that translator will be applied. + +If there are multiple pybind11 modules that share exception types (either +standard built-in or custom) loaded into a single python instance and +consistent error handling behavior is needed, then local translators should be +used. + +Changing the previous example to use ``register_local_exception_translator`` +would mean that when invalid_argument is thrown in the module2 code, the +module2 translator will always handle it, while in module1, the module1 +translator will do the same. + .. _handling_python_exceptions_cpp: Handling exceptions from Python in C++ diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h index 5fee3318b..15e09165d 100644 --- a/include/pybind11/detail/class.h +++ b/include/pybind11/detail/class.h @@ -209,7 +209,7 @@ extern "C" inline void pybind11_meta_dealloc(PyObject *obj) { internals.direct_conversions.erase(tindex); if (tinfo->module_local) - registered_local_types_cpp().erase(tindex); + get_local_internals().registered_types_cpp.erase(tindex); else internals.registered_types_cpp.erase(tindex); internals.registered_types_py.erase(tinfo->type); diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h index 5578c6516..a621aed2a 100644 --- a/include/pybind11/detail/internals.h +++ b/include/pybind11/detail/internals.h @@ -12,7 +12,11 @@ #include "../pytypes.h" PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE) + +using ExceptionTranslator = void (*)(std::exception_ptr); + PYBIND11_NAMESPACE_BEGIN(detail) + // Forward declarations inline PyTypeObject *make_static_property_type(); inline PyTypeObject *make_default_metaclass(); @@ -100,7 +104,7 @@ struct internals { std::unordered_set, override_hash> inactive_override_cache; type_map> direct_conversions; std::unordered_map> patients; - std::forward_list registered_exception_translators; + std::forward_list registered_exception_translators; std::unordered_map shared_data; // Custom data to be shared across extensions std::vector loader_patient_stack; // Used by `loader_life_support` std::forward_list static_strings; // Stores the std::strings backing detail::c_str() @@ -313,12 +317,25 @@ PYBIND11_NOINLINE inline internals &get_internals() { return **internals_pp; } -/// Works like `internals.registered_types_cpp`, but for module-local registered types: -inline type_map ®istered_local_types_cpp() { - static type_map locals{}; - return locals; + +// the internals struct (above) is shared between all the modules. local_internals are only +// for a single module. Any changes made to internals may require an update to +// PYBIND11_INTERNALS_VERSION, breaking backwards compatibility. local_internals is, by design, +// restricted to a single module. Whether a module has local internals or not should not +// impact any other modules, because the only things accessing the local internals is the +// module that contains them. +struct local_internals { + type_map registered_types_cpp; + std::forward_list registered_exception_translators; +}; + +/// Works like `get_internals`, but for things which are locally registered. +inline local_internals &get_local_internals() { + static local_internals locals; + return locals; } + /// Constructs a std::string with the given arguments, stores it in `internals`, and returns its /// `c_str()`. Such strings objects have a long storage duration -- the internal strings are only /// cleared when the program exits or after interpreter shutdown (when embedding), and so are diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h index 451690dc7..bdf3a3982 100644 --- a/include/pybind11/detail/type_caster_base.h +++ b/include/pybind11/detail/type_caster_base.h @@ -160,7 +160,7 @@ PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) { } inline detail::type_info *get_local_type_info(const std::type_index &tp) { - auto &locals = registered_local_types_cpp(); + auto &locals = get_local_internals().registered_types_cpp; auto it = locals.find(tp); if (it != locals.end()) return it->second; diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h index af8e730d3..0c25ca1a2 100644 --- a/include/pybind11/pybind11.h +++ b/include/pybind11/pybind11.h @@ -56,6 +56,29 @@ PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE) +PYBIND11_NAMESPACE_BEGIN(detail) + +// Apply all the extensions translators from a list +// Return true if one of the translators completed without raising an exception +// itself. Return of false indicates that if there are other translators +// available, they should be tried. +inline bool apply_exception_translators(std::forward_list& translators) { + auto last_exception = std::current_exception(); + + for (auto &translator : translators) { + try { + translator(last_exception); + return true; + } catch (...) { + last_exception = std::current_exception(); + } + } + return false; +} + +PYBIND11_NAMESPACE_END(detail) + + /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object class cpp_function : public function { public: @@ -550,6 +573,7 @@ protected: } } + /// Main dispatch logic for calls to functions bound using pybind11 static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) { using namespace detail; @@ -830,8 +854,12 @@ protected: #endif } catch (...) { /* When an exception is caught, give each registered exception - translator a chance to translate it to a Python exception - in reverse order of registration. + translator a chance to translate it to a Python exception. First + all module-local translators will be tried in reverse order of + registration. If none of the module-locale translators handle + the exception (or there are no module-locale translators) then + the global translators will be tried, also in reverse order of + registration. A translator may choose to do one of the following: @@ -840,17 +868,15 @@ protected: - do nothing and let the exception fall through to the next translator, or - delegate translation to the next translator by throwing a new type of exception. */ - auto last_exception = std::current_exception(); - auto ®istered_exception_translators = get_internals().registered_exception_translators; - for (auto& translator : registered_exception_translators) { - try { - translator(last_exception); - } catch (...) { - last_exception = std::current_exception(); - continue; - } + auto &local_exception_translators = get_local_internals().registered_exception_translators; + if (detail::apply_exception_translators(local_exception_translators)) { return nullptr; } + auto &exception_translators = get_internals().registered_exception_translators; + if (detail::apply_exception_translators(exception_translators)) { + return nullptr; + } + PyErr_SetString(PyExc_SystemError, "Exception escaped from default exception translator!"); return nullptr; } @@ -951,6 +977,7 @@ protected: } }; + /// Wrapper for Python extension modules class module_ : public object { public: @@ -1124,7 +1151,7 @@ protected: auto tindex = std::type_index(*rec.type); tinfo->direct_conversions = &internals.direct_conversions[tindex]; if (rec.module_local) - registered_local_types_cpp()[tindex] = tinfo; + get_local_internals().registered_types_cpp[tindex] = tinfo; else internals.registered_types_cpp[tindex] = tinfo; internals.registered_types_py[(PyTypeObject *) m_ptr] = { tinfo }; @@ -1310,7 +1337,7 @@ public: generic_type::initialize(record); if (has_alias) { - auto &instances = record.module_local ? registered_local_types_cpp() : get_internals().registered_types_cpp; + auto &instances = record.module_local ? get_local_internals().registered_types_cpp : get_internals().registered_types_cpp; instances[std::type_index(typeid(type_alias))] = instances[std::type_index(typeid(type))]; } } @@ -2010,12 +2037,24 @@ template void implicitly_convertible() pybind11_fail("implicitly_convertible: Unable to find type " + type_id()); } -template -void register_exception_translator(ExceptionTranslator&& translator) { + +inline void register_exception_translator(ExceptionTranslator &&translator) { detail::get_internals().registered_exception_translators.push_front( std::forward(translator)); } + +/** + * Add a new module-local exception translator. Locally registered functions + * will be tried before any globally registered exception translators, which + * will only be invoked if the module-local handlers do not deal with + * the exception. + */ +inline void register_local_exception_translator(ExceptionTranslator &&translator) { + detail::get_local_internals().registered_exception_translators.push_front( + std::forward(translator)); +} + /** * Wrapper to generate a new Python exception type. * @@ -2049,22 +2088,20 @@ PYBIND11_NAMESPACE_BEGIN(detail) // directly in register_exception, but that makes clang <3.5 segfault - issue #1349). template exception &get_exception_object() { static exception ex; return ex; } -PYBIND11_NAMESPACE_END(detail) -/** - * Registers a Python exception in `m` of the given `name` and installs an exception translator to - * translate the C++ exception to the created Python exception using the exceptions what() method. - * This is intended for simple exception translations; for more complex translation, register the - * exception object and translator directly. - */ +// Helper function for register_exception and register_local_exception template -exception ®ister_exception(handle scope, - const char *name, - handle base = PyExc_Exception) { +exception ®ister_exception_impl(handle scope, + const char *name, + handle base, + bool isLocal) { auto &ex = detail::get_exception_object(); if (!ex) ex = exception(scope, name, base); - register_exception_translator([](std::exception_ptr p) { + auto register_func = isLocal ? ®ister_local_exception_translator + : ®ister_exception_translator; + + register_func([](std::exception_ptr p) { if (!p) return; try { std::rethrow_exception(p); @@ -2075,6 +2112,36 @@ exception ®ister_exception(handle scope, return ex; } +PYBIND11_NAMESPACE_END(detail) + +/** + * Registers a Python exception in `m` of the given `name` and installs a translator to + * translate the C++ exception to the created Python exception using the what() method. + * This is intended for simple exception translations; for more complex translation, register the + * exception object and translator directly. + */ +template +exception ®ister_exception(handle scope, + const char *name, + handle base = PyExc_Exception) { + return detail::register_exception_impl(scope, name, base, false /* isLocal */); +} + +/** + * Registers a Python exception in `m` of the given `name` and installs a translator to + * translate the C++ exception to the created Python exception using the what() method. + * This translator will only be used for exceptions that are thrown in this module and will be + * tried before global exception translators, including those registered with register_exception. + * This is intended for simple exception translations; for more complex translation, register the + * exception object and translator directly. + */ +template +exception ®ister_local_exception(handle scope, + const char *name, + handle base = PyExc_Exception) { + return detail::register_exception_impl(scope, name, base, true /* isLocal */); +} + PYBIND11_NAMESPACE_BEGIN(detail) PYBIND11_NOINLINE inline void print(const tuple &args, const dict &kwargs) { auto strings = tuple(args.size()); diff --git a/tests/local_bindings.h b/tests/local_bindings.h index 8629ed778..f11c08e61 100644 --- a/tests/local_bindings.h +++ b/tests/local_bindings.h @@ -35,6 +35,25 @@ using NonLocalVec2 = std::vector; using NonLocalMap = std::unordered_map; using NonLocalMap2 = std::unordered_map; + +// Exception that will be caught via the module local translator. +class LocalException : public std::exception { +public: + explicit LocalException(const char * m) : message{m} {} + const char * what() const noexcept override {return message.c_str();} +private: + std::string message = ""; +}; + +// Exception that will be registered with register_local_exception_translator +class LocalSimpleException : public std::exception { +public: + explicit LocalSimpleException(const char * m) : message{m} {} + const char * what() const noexcept override {return message.c_str();} +private: + std::string message = ""; +}; + PYBIND11_MAKE_OPAQUE(LocalVec); PYBIND11_MAKE_OPAQUE(LocalVec2); PYBIND11_MAKE_OPAQUE(LocalMap); diff --git a/tests/pybind11_cross_module_tests.cpp b/tests/pybind11_cross_module_tests.cpp index e79701c6c..4bfd5302d 100644 --- a/tests/pybind11_cross_module_tests.cpp +++ b/tests/pybind11_cross_module_tests.cpp @@ -29,11 +29,14 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) { bind_local(m, "ExternalType2", py::module_local()); // test_exceptions.py + py::register_local_exception(m, "LocalSimpleException"); m.def("raise_runtime_error", []() { PyErr_SetString(PyExc_RuntimeError, "My runtime error"); throw py::error_already_set(); }); m.def("raise_value_error", []() { PyErr_SetString(PyExc_ValueError, "My value error"); throw py::error_already_set(); }); m.def("throw_pybind_value_error", []() { throw py::value_error("pybind11 value error"); }); m.def("throw_pybind_type_error", []() { throw py::type_error("pybind11 type error"); }); m.def("throw_stop_iteration", []() { throw py::stop_iteration(); }); + m.def("throw_local_error", []() { throw LocalException("just local"); }); + m.def("throw_local_simple_error", []() { throw LocalSimpleException("external mod"); }); py::register_exception_translator([](std::exception_ptr p) { try { if (p) std::rethrow_exception(p); @@ -42,6 +45,17 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) { } }); + // translate the local exception into a key error but only in this module + py::register_local_exception_translator([](std::exception_ptr p) { + try { + if (p) { + std::rethrow_exception(p); + } + } catch (const LocalException &e) { + PyErr_SetString(PyExc_KeyError, e.what()); + } + }); + // test_local_bindings.py // Local to both: bind_local(m, "LocalType", py::module_local()) @@ -94,7 +108,7 @@ PYBIND11_MODULE(pybind11_cross_module_tests, m) { m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); }); // test_internal_locals_differ - m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); }); + m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; }); // test_stl_caster_vs_stl_bind py::bind_vector>(m, "VectorInt"); diff --git a/tests/test_exceptions.cpp b/tests/test_exceptions.cpp index f7bacd07e..e28f0bb79 100644 --- a/tests/test_exceptions.cpp +++ b/tests/test_exceptions.cpp @@ -6,9 +6,10 @@ All rights reserved. Use of this source code is governed by a BSD-style license that can be found in the LICENSE file. */ - #include "test_exceptions.h" +#include "local_bindings.h" + #include "pybind11_tests.h" #include @@ -68,6 +69,17 @@ class MyException5_1 : public MyException5 { using MyException5::MyException5; }; + +// Exception that will be caught via the module local translator. +class MyException6 : public std::exception { +public: + explicit MyException6(const char * m) : message{m} {} + const char * what() const noexcept override {return message.c_str();} +private: + std::string message = ""; +}; + + struct PythonCallInDestructor { PythonCallInDestructor(const py::dict &d) : d(d) {} ~PythonCallInDestructor() { d["good"] = true; } @@ -138,14 +150,29 @@ TEST_SUBMODULE(exceptions, m) { // A slightly more complicated one that declares MyException5_1 as a subclass of MyException5 py::register_exception(m, "MyException5_1", ex5.ptr()); + //py::register_local_exception(m, "LocalSimpleException") + + py::register_local_exception_translator([](std::exception_ptr p) { + try { + if (p) { + std::rethrow_exception(p); + } + } catch (const MyException6 &e) { + PyErr_SetString(PyExc_RuntimeError, e.what()); + } + }); + m.def("throws1", []() { throw MyException("this error should go to a custom type"); }); m.def("throws2", []() { throw MyException2("this error should go to a standard Python exception"); }); m.def("throws3", []() { throw MyException3("this error cannot be translated"); }); m.def("throws4", []() { throw MyException4("this error is rethrown"); }); m.def("throws5", []() { throw MyException5("this is a helper-defined translated exception"); }); m.def("throws5_1", []() { throw MyException5_1("MyException5 subclass"); }); + m.def("throws6", []() { throw MyException6("MyException6 only handled in this module"); }); m.def("throws_logic_error", []() { throw std::logic_error("this error should fall through to the standard handler"); }); - m.def("throws_overflow_error", []() {throw std::overflow_error(""); }); + m.def("throws_overflow_error", []() { throw std::overflow_error(""); }); + m.def("throws_local_error", []() { throw LocalException("never caught"); }); + m.def("throws_local_simple_error", []() { throw LocalSimpleException("this mod"); }); m.def("exception_matches", []() { py::dict foo; try { diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py index b9fc26938..966ae07fc 100644 --- a/tests/test_exceptions.py +++ b/tests/test_exceptions.py @@ -25,7 +25,7 @@ def test_error_already_set(msg): assert msg(excinfo.value) == "foo" -def test_cross_module_exceptions(): +def test_cross_module_exceptions(msg): with pytest.raises(RuntimeError) as excinfo: cm.raise_runtime_error() assert str(excinfo.value) == "My runtime error" @@ -45,6 +45,15 @@ def test_cross_module_exceptions(): with pytest.raises(StopIteration) as excinfo: cm.throw_stop_iteration() + with pytest.raises(cm.LocalSimpleException) as excinfo: + cm.throw_local_simple_error() + assert msg(excinfo.value) == "external mod" + + with pytest.raises(KeyError) as excinfo: + cm.throw_local_error() + # KeyError is a repr of the key, so it has an extra set of quotes + assert str(excinfo.value) == "'just local'" + # TODO: FIXME @pytest.mark.xfail( @@ -221,3 +230,21 @@ def test_invalid_repr(): with pytest.raises(TypeError): m.simple_bool_passthrough(MyRepr()) + + +def test_local_translator(msg): + """Tests that a local translator works and that the local translator from + the cross module is not applied""" + with pytest.raises(RuntimeError) as excinfo: + m.throws6() + assert msg(excinfo.value) == "MyException6 only handled in this module" + + with pytest.raises(RuntimeError) as excinfo: + m.throws_local_error() + assert not isinstance(excinfo.value, KeyError) + assert msg(excinfo.value) == "never caught" + + with pytest.raises(Exception) as excinfo: + m.throws_local_simple_error() + assert not isinstance(excinfo.value, cm.LocalSimpleException) + assert msg(excinfo.value) == "this mod" diff --git a/tests/test_local_bindings.cpp b/tests/test_local_bindings.cpp index bfbab3ed3..8d6e33f79 100644 --- a/tests/test_local_bindings.cpp +++ b/tests/test_local_bindings.cpp @@ -78,7 +78,7 @@ TEST_SUBMODULE(local_bindings, m) { m.def("get_mixed_lg", [](int i) { return MixedLocalGlobal(i); }); // test_internal_locals_differ - m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::registered_local_types_cpp(); }); + m.def("local_cpp_types_addr", []() { return (uintptr_t) &py::detail::get_local_internals().registered_types_cpp; }); // test_stl_caster_vs_stl_bind m.def("load_vector_via_caster", [](std::vector v) {