* Put bakein branch @ 18b72c0ffa on top of smart_holder branch:
Commands used:
```
git checkout bakein
git diff smart_holder > ~/zd
git checkout smart_holder
git checkout -b bakein_sh
patch -p 1 < ~/zd
git checkout smart_holder \
MANIFEST.in \
README.rst \
README_smart_holder.rst \
docs/advanced/smart_ptrs.rst \
ubench/holder_comparison.cpp \
ubench/holder_comparison.py \
ubench/holder_comparison_extract_sheet_data.py \
ubench/number_bucket.h \
ubench/python/number_bucket.clif
git add -A
```
* Add back README_smart_holder.rst in tests/extra_python_package/test_files.py
* Restore smart_holder_poc.h as-is on smart_holder branch (i.e. undo `PYBIND11_SMART_HOLDER_PADDING`, which was meant for stress-testing only).
* Insert `std::move()` as suggested by @laramiel
* `property_cpp_function_sh_*` named specializations, as suggested by @laramiel (https://github.com/pybind/pybind11/pull/5257#discussion_r1688346807)
* Call `property_cpp_function_classic` member functions, rather than inlining the implementations.
* Use `PYBIND11_HAVE_INTERNALS_WITH_SMART_HOLDER_SUPPORT` in holder_comparison.cpp (holder_comparison.py is NOT changed accordingly in this commit, i.e. can still only be run if the smart_holder functionality is available).
* Systematically rename `loaded_as` to `load_as` (`shared_ptr`, `unique_ptr`) as suggested by @laramiel
* Make change as suggested by @laramiel. This makes it much more obvious that the latest implementation of `smart_holder_from_unique_ptr()` accepts all existing `return_value_policy` enum values except `copy`.
* Resolve `BAKEIN_WIP: Rewrite comment.` for `property_cpp_function_*` specializations.
* Resolve `BAKEIN_WIP: Add comment to explain: This is meant for stress-testing only.`
* Resolve all remaining BAKEIN_WIP (in pybind11/cast.h).
Leave only two pairs of SMART_HOLDER_BAKEIN_FOLLOW_ON comments: refactoring of copyable_holder_caster, move_only_holder_caster. This is best left until after the smart_holder branch is merged into the master branch.
* Remove obsolete `using holder_type = smart_holder;` in `load_helper`
* Add SMART_HOLDER_BAKEIN_FOLLOW_ON comment for `internals::default_holder`
* README_smart_holder.rst update (line count reduced from 356 to 123).
* Adding test_unique_ptr_member (for desired PyCLIF behavior).
See also: https://github.com/pybind/pybind11/issues/2583
Does not build with upstream master or
https://github.com/pybind/pybind11/pull/2047, but builds with
https://github.com/RobotLocomotion/pybind11 and almost runs:
```
Running tests in directory "/usr/local/google/home/rwgk/forked/EricCousineau-TRI/pybind11/tests":
================================================================================= test session starts =================================================================================
platform linux -- Python 3.8.5, pytest-5.4.3, py-1.9.0, pluggy-0.13.1
rootdir: /usr/local/google/home/rwgk/forked/EricCousineau-TRI/pybind11/tests, inifile: pytest.ini
collected 2 items
test_unique_ptr_member.py .F [100%]
====================================================================================== FAILURES =======================================================================================
_____________________________________________________________________________ test_pointee_and_ptr_owner ______________________________________________________________________________
def test_pointee_and_ptr_owner():
obj = m.pointee()
assert obj.get_int() == 213
m.ptr_owner(obj)
with pytest.raises(ValueError) as exc_info:
> obj.get_int()
E Failed: DID NOT RAISE <class 'ValueError'>
test_unique_ptr_member.py:17: Failed
============================================================================= 1 failed, 1 passed in 0.06s =============================================================================
```
* unique_ptr or shared_ptr return
* new test_variant_unique_shared with vptr_holder prototype
* moving prototype code to pybind11/vptr_holder.h, adding type_caster specialization to make the bindings involving unique_ptr passing compile, but load and cast implementations are missing
* disabling GitHub Actions on pull_request (for this PR)
* disabling AppVeyor (for this PR)
* TRIGGER_SEGSEV macro, annotations for GET_STACK (vptr::get), GET_INT_STACK (pointee)
* adding test_promotion_of_disowned_to_shared
* Copying tests as-is from xxx_value_ptr_xxx_holder branch.
https://github.com/rwgk/pybind11/tree/xxx_value_ptr_xxx_holder
Systematically exercising returning and passing unique_ptr<T>, shared_ptr<T>
with unique_ptr, shared_ptr holder.
Observations:
test_holder_unique_ptr:
make_unique_pointee OK
pass_unique_pointee BUILD_FAIL (as documented)
make_shared_pointee Abort free(): double free detected
pass_shared_pointee RuntimeError: Unable to load a custom holder type from a default-holder instance
test_holder_shared_ptr:
make_unique_pointee Segmentation fault (#1138)
pass_unique_pointee BUILD_FAIL (as documented)
make_shared_pointee OK
pass_shared_pointee OK
* Copying tests as-is from xxx_value_ptr_xxx_holder branch.
https://github.com/rwgk/pybind11/tree/xxx_value_ptr_xxx_holder
Systematically exercising casting between shared_ptr<base>, shared_ptr<derived>.
* Demonstration of Undefined Behavior in handling of shared_ptr holder.
Based on https://godbolt.org/z/4fdjaW by jorgbrown@ (thanks Jorg!).
* Additional demonstration of Undefined Behavior in handling of shared_ptr holder.
* fixing up-down mixup in comment
* Demonstration of Undefined Behavior in handling of polymorphic pointers.
(This demo does NOT involve smart pointers at all, unlike the otherwise similar test_smart_ptr_private_first_base.)
* minor test_private_first_base.cpp simplification (after discovering that this can be wrapped with Boost.Python, using boost::noncopyable)
* pybind11 equivalent of Boost.Python test similar to reproducer under #1333
* Snapshot of WIP, TODO: shared_ptr deleter with on/off switch
* Adding vptr_deleter.
* Adding from/as unique_ptr<T> and unique_ptr<T, D>.
* Adding from_shared_ptr. Some polishing.
* New tests/core/smart_holder_poc_test.cpp, using Catch2.
* Adding in vptr_deleter_guard_flag.
* Improved labeling of TEST_CASEs.
* Shuffling existing TEST_CASEs into systematic matrix.
* Implementing all [S]uccess tests.
* Implementing all [E]xception tests.
* Testing of exceptions not covered by the from-as matrix.
* Adding top-level comment.
* Converting from methods to factory functions (no functional change).
* Removing obsolete and very incomplete test (replaced by Catch2-based test).
* Removing stray file.
* Adding type_caster_bare_interface_demo.
* Adding shared_ptr<mpty>, shared_ptr<mpty const> casters.
* Adding unique_ptr<mpty>, unique_ptr<mpty const> casters.
* Pure copy of `class class_` implementation in pybind11.h (master commit 98f1bbb800).
* classh.h: renaming of class_ to classh + namespace; forking test_classh_wip from test_type_caster_bare_interface_demo.
* Hard-coding smart_holder into classh.
* Adding mpty::mtxt string member.
* Adding isinstance<mpty> in type_caster::load functions.
* Adding rvalue_ref, renaming const_value_ref to lvalue_ref & removing const.
* Retrieving smart_holder pointer in type_caster<mpty>::load, and using it cast_op operators.
* Factoring out smart_holder_type_caster_load.
* Retrieving smart_holder pointer in type_caster<std::shared_ptr<mpty[ const]>>::load, and using it cast_op operators.
* Improved error messaging: Cannot disown nullptr (as_unique_ptr).
* Retrieving smart_holder pointer in type_caster<std::unique_ptr<mpty[ const]>>::load, and using it cast_op operators.
* Pure `clang-format --style=file -i` change.
* Pure `clang-format --style=file -i` change, with two `clang-format off` directives.
* Fixing oversight (discovered by flake8).
* flake8 cleanup
* Systematically setting mtxt for all rtrn_mpty_* functions (preparation, the values are not actually used yet).
* static cast handle for rtrn_cptr works by simply dropping in code from type_caster_base (marked with comments).
* static cast handle for rtrn_cref works by simply dropping in code from type_caster_base (marked with comments). rtrn_mref and rtrn_mptr work via const_cast (to add const).
* static cast handle for rtrn_valu works by simply dropping in code from type_caster_base (marked with comments). rtrn_rref raises a RuntimeError, to be investigated.
* Copying type_caster_generic::cast into type_caster<mpty> as-is (preparation for handling smart pointers).
* Pure clang-format change (applied to original type_caster_generic::cast).
* Adding comment re potential use_count data race.
* static handle cast implementations for rtrn_shmp, rtrn_shcp.
* Adding MISSING comments in operator std::unique_ptr<mpty[ const]>.
* static handle cast implementations for rtrn_uqmp, rtrn_uqcp.
* Bug fix: vptr_deleter_armed_flag_ptr has to live on the heap.
See new bullet point in comment section near the top.
The variable was also renamed to reflect its function more accurately.
* Fixing bugs discovered by ASAN. The code is now ASAN, MSAN, UBSAN clean.
* Making test_type_caster_bare_interface_demo.cpp slightly more realistic, ASAN, MSAN, UBSAN clean.
* Calling deregister_instance after disowning via unique_ptr.
* Removing enable_shared_from_this stub, simplifying existing code, clang-format.
Open question, with respect to the original code:
76a160070b/include/pybind11/pybind11.h (L1510)
To me it looks like the exact situation marked as `std::shared_ptr<Good> gp1 = not_so_good.getptr();` here: https://en.cppreference.com/w/cpp/memory/enable_shared_from_this
The comment there is: `// undefined behavior (until C++17) and std::bad_weak_ptr thrown (since C++17)`
Does the existing code have UB pre C++17?
I'll leave handling of enable_shared_from_this for later, as the need arises.
* Cosmetical change around helper functions.
* Using type_caster_base<mpty>::src_and_type directly, removing copy. Also renaming one cast to cast_const_raw_ptr, for clarity.
* Fixing clang-format oversight.
* Using factored-out make_constructor (PR #2798), removing duplicate code.
* Inserting additional assert to ensure a returned unique_ptr is always a new Python instance.
* Adding minor comment (change to internals needed to distinguish uninitialized/disowned in error message).
* Factoring out find_existing_python_instance().
* Moving factored-out make_constructor to test_classh_wip.cpp, restoring previous version of cast.h. This is currently the most practical approach. See PR #2798 for background.
* Copying classh type_casters from test_classh_wip.cpp UNMODIFIED, as a baseline for generalizing the code.
* Using pybind11/detail/classh_type_casters.h from test_classh_wip.cpp.
* Adding & using PYBIND11_CLASSH_TYPE_CASTERS define.
* Adding test_classh_inheritance, currently failing (passes with class_).
* Removing .clang-format before git rebase master (where the file was added).
* Bringing back .clang-format, the previous rm was a bad idea.
* Folding in modified_type_caster_generic_load_impl, just enough to pass test_class_wip. test_classh_inheritance is still failing, but with a different error: [RuntimeError: Incompatible type (as_raw_ptr_unowned).]
* Minimal changes needed to pass test_classh_inheritance.
* First pass adjusting try_implicit_casts and try_load_foreign_module_local to capture loaded_v_h, but untested and guarded with pybind11_failure("Untested"). This was done mainly to determine general feasibility. Note the TODO in pybind11.h, where type_caster_generic::local_load is currently hard-coded. test_classh_wip and test_classh_inheritance still pass, as before.
* Decoupling generic_type from type_caster_generic.
* Changes and tests covering classh_type_casters try_implicit_casts.
* Minimal test covering classh_type_casters load_impl Case 2b.
* Removing stray isinstance<T>(src): it interferes with the py::module_local feature. Adding missing #includes.
* Tests for classh py::module_local() feature.
* Pure renaming of function names in test_classh_inheritance, similar to the systematic approach used in test_class_wip. NO functional changes.
* Pure renaming of function and variable names, for better generalization when convoluting with inheritance. NO functional changes.
* Adopting systematic naming scheme from test_classh_wip. NO functional changes.
* Moving const after type name, for functions that cover a systematic scheme. NO functional changes.
* Adding smart_holder_type_caster_load::loaded_as_shared_ptr, currently bypassing smart_holder shared_ptr tracking completely, but the tests pass and are sanitizer clean.
* Removing rtti_held from smart_holder. See updated comment.
* Cleaning up loaded_as_raw_ptr_unowned, loaded_as_shared_ptr.
* Factoring out convert_type and folding into loaded_as_unique_ptr.
* Folding convert_type into lvalue_ref and rvalue_ref paths. Some smart_holder_type_caster_load cleanup.
* Using unique_ptr in local_load to replace static variable. Also adding local_load_safety_guard.
* Converting test_unique_ptr_member to using classh: fully working, ASAN, MSAN, UBSAN clean.
* Removing debugging comments (GET_STACK, GET_INT_STACK). cast.h is identical to current master again, pybind11.h only has the generic_type::initialize(..., &type_caster_generic::local_load) change.
* Purging obsolete pybind11/vptr_holder.h and associated test.
* Moving several tests to github.com/rwgk/rwgk_tbx/tree/main/pybind11_tests
a2c2f88174
These tests are from experimenting, and for demonstrating UB in pybind11 multiple inheritance handling ("first_base"), to be fixed later.
* Adding py::smart_holder support to py::class_, purging py::classh completely.
* Renaming files in include directory, creating pybind11/smart_holder.h.
* Renaming all "classh" to "smart_holder" in pybind11/detail/smart_holder_type_casters.h.
The user-facing macro is now PYBIND11_SMART_HOLDER_TYPE_CASTERS.
* Systematically renaming tests to use "class_sh" in the name.
* Renaming test_type_caster_bare_interface_demo to test_type_caster_bare_interface.
* Renaming new tests/core subdirectory to tests/pure_cpp.
* Adding new tests to CMake config, resetting CI config.
* Changing CMake file so that test_class_sh_module_local.py actually runs.
* clang-tidy fixes.
* 32-bit compatibility.
* Reusing type_caster_base make_copy_constructor, make_move_constructor with a trick.
* CMake COMPARE NATURAL is not available with older versions.
* Adding copyright notices to new header files.
* Explicitly define copy/move constructors/assignments.
* Adding new header files to tests/extra_python_package/test_files.py.
* Adding tests/pure_cpp/CMakeLists.txt.
* Making use of the new find_existing_python_instance() function factored out with PR #2822.
* Moving define PYBIND11_SMART_HOLDER_TYPE_CASTERS(T) down in the file. NO functional changes. Preparation for follow-up work (to keep that diff smaller).
* Reintroducing py::classh, this time as a simple alias for py::class_<U, py::smart_holder>.
* Replacing detail::is_smart_holder<H> in cast.h with detail::is_smart_holder_type_caster<T>.
Moving get_local_load_function_ptr, init_instance_for_type to smart_holder_type_caster_class_hooks.
Expanding static_assert in py::type::handle_of<> to accommodate smart_holder_type_casters.
* Fixing oversight.
* Adding classu alias for class_<U, std::unique_ptr<U>>.
* Giving up on idea to use legacy init_instance only if is_base_of<type_caster_generic, type_caster<T>. There are use cases in the wild that define both a custom type_caster and class_.
* Removing test_type_caster_bare_interface, which was moved to the separate PR #2834.
* Moving up is_smart_holder_type_caster, to also use in cast_is_temporary_value_reference.
* Adding smart_holder_type_casters for unique_ptr with custom deleter. SEVERE CODE DUPLICATION. This commit is to establish a baseline for consolidating the unique_ptr code.
* Unification of unique_ptr, unique_ptr_with_deleter code in smart_holder_poc.h. Leads to more fitting error messages. Enables use of unique_ptr<T, D> smart_holder_type_casters also for unique_ptr<T>.
* Copying files as-is from branch test_unique_ptr_member (PR #2672).
* Adding comment, simplifying naming, cmake addition.
* Introducing PYBIND11_USE_SMART_HOLDER_AS_DEFAULT macro (tested only undefined; there are many errors with the macro defined).
* Removing test_type_caster_bare_interface, which was moved to the separate PR #2834.
* Fixing oversight introduced with commit 95425f13d6.
* Setting record.default_holder correctly for PYBIND11_USE_SMART_HOLDER_AS_DEFAULT.
With this test_class.cpp builds and even mostly runs, except
`test_multiple_instances_with_same_pointer`, which segfaults because it is
using a `unique_ptr` holder but `smart_holder` `type_caster`.
Also adding `static_assert`s to generate build errors for such situations,
but guarding with `#if 0` to first pivot to test_factory_constructors.cpp.
* Fixing up cast.h and smart_holder.h after rebase.
* Removing detail/smart_holder_type_casters.h in separate commit.
* Commenting out const in def_buffer(... const). With this, test_buffers builds and runs with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT. Explanation why the const needs to be removed, or fix elsewhere, is still needed, but left for later.
* Adding test_class_sh_factory_constructors, reproducing test_factory_constructors failure. Using py::class_ in this commit, to be changed to py::classh for debugging.
* Removing include/pybind11/detail/smart_holder_type_casters.h from CMakeLists.txt, test_files.py (since it does not exist in this branch).
* Adding // DANGER ZONE reminders.
* Converting as many py::class_ to py::classh as possible, not breaking tests.
* Adding initimpl::construct() overloads, resulting in test_class_sh_factory_constructors feature parity for py::class_ and py::classh.
* Adding enable_if !is_smart_holder_type_caster to existing initimpl::construct(). With this test_factory_constructors.cpp builds with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT.
* Disabling shared_ptr&, shared_ptr* tests when building with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT for now, pending work on smart_holder_type_caster<shared_ptr>.
* Factoring out struct and class definitions into anonymous namespace. Preparation for building with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT.
* Simplifying from_unique_ptr(): typename D = std::default_delete<T> is not needed. Factoring out is_std_default_delete<T>() for consistentcy between ensure_compatible_rtti_uqp_del() and from_unique_ptr().
* Introducing PYBIND11_SMART_POINTER_HOLDER_TYPE_CASTERS. Using it in test_smart_ptr.cpp. With this test_smart_ptr builds with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT and all but one test run successfully.
* Introducing 1. type_caster_for_class_, used in PYBIND11_MAKE_OPAQUE, and 2. default_holder_type, used in stl_bind.h.
* Using __VA_ARGS__ in PYBIND11_SMART_POINTER_HOLDER_TYPE_CASTERS.
* Replacing condense_for_macro with much simpler approach.
* Softening static_assert, to only check specifically that smart_holder is not mixed with type_caster_base, and unique_ptr/shared_ptr holders are not mixed with smart_holder_type_casters.
* Adding PYBIND11_SMART_POINTER_HOLDER_TYPE_CASTERS in test_class.cpp (with this all but one test succeed with PYBIND11_USE_SMART_HOLDER_AS_DEFAULT).
* Adding remaining PYBIND11_SMART_POINTER_HOLDER_TYPE_CASTERS. static_assert for "necessary conditions" for both types of default holder, static_assert for "strict conditions" guarded by new PYBIND11_STRICT_ASSERTS_CLASS_HOLDER_VS_TYPE_CASTER_MIX. All tests build & run as before with unique_ptr as the default holder, all tests build for smart_holder as the default holder, even with the strict static_assert.
* Introducing check_is_smart_holder_type_caster() function for runtime check, and reinterpreting record.default_holder as "uses_unique_ptr_holder". With this test_smart_ptr succeeds. (All 42 tests build, 35 tests succeed, 5 run but have some failures, 2 segfault.)
* Bug fix: Adding have_value() to smart_holder_type_caster_load. With this test_builtin_casters succeeds. (All 42 tests build, 36 tests succeed, 5 run but have some failures, 1 segfault.)
* Adding unowned_void_ptr_from_direct_conversion to modified_type_caster_generic_load_impl. This fixes the last remaining segfault (test_numpy_dtypes). New stats for all tests combined: 12 failed, 458 passed.
* Adding "Lazy allocation for unallocated values" (for old-style __init__) into load_value_and_holder. Deferring destruction of disowned holder until clear_instance, to remain inspectable for "uninitialized" or "disowned" detection. New stats for all tests combined: 5 failed, 465 passed.
* Changing std::shared_ptr pointer/reference to const pointer/reference. New stats for all tests combined: 4 failed, 466 passed.
* Adding return_value_policy::move to permissible policies for unique_ptr returns. New stats for all tests combined: 3 failed, 467 passed.
* Overlooked flake8 fixes.
* Manipulating failing ConstructorStats test to pass, to be able to run all tests with ASAN.
This version of the code is ASAN clean with unique_ptr or smart_holder as the default.
This change needs to be reverted after adopting the existing move-only-if-refcount-is-1
logic used by type_caster_base.
* Adding copy constructor and move constructor tracking to atyp. Preparation for a follow-up change in smart_holder_type_caster, to make this test sensitive to the changing behavior.
[skip ci]
* Removing `operator T&&() &&` from smart_holder_type_caster, for compatibility with the behavior of type_caster_base. Enables reverting 2 of 3 test manipulations applied under commit 249df7cbdb. The manipulation in test_factory_constructors.py is NOT reverted in this commit.
[skip ci]
* Fixing unfortunate editing mishap. This reverts the last remaining test manipulation in commit 249df7cbdb and makes all existing unit tests pass with smart_holder as default holder.
* GitHub CI clang-tidy fixes.
* Adding messages to terse `static_assert`s, for pre-C++17 compatibility.
* Using @pytest.mark.parametrize to run each assert separately (to see all errors, not just the first).
* Systematically removing _atyp from function names, to make the test code simpler.
* Using re.match to accommodate variable number of intermediate MvCtor.
* Also removing `operator T()` from smart_holder_type_caster, to fix gcc compilation errors. The only loss is pass_rref in test_class_sh_basic.
* Systematically replacing `detail::enable_if_t<...smart_holder...>` with `typename std::enable_if<...smart_holder...>::type`. Attempt to work around MSVC 2015 issues, to be tested via GitHub CI. The idea for this change originates from this comment: https://github.com/pybind/pybind11/issues/1616#issuecomment-444536813
* Importing re before pytest after observing a PyPy CI flake when importing pytest first.
* Copying MSVC 2015 compatibility change from branch pr2672_use_smart_holder_as_default.
* Introducing is_smart_holder_type_caster_base_tag, to keep smart_holder code more disconnected.
* Working around MSVC 2015 bug.
* Expanding comment for MSVC 2015 workaround.
* Systematically changing std::enable_if back to detail::enable_if_t, effectively reverting commit 5d4b6890a3.
* Removing unused smart_holder_type_caster_load::loaded_as_rvalue_ref (it was an oversight that it was not removed with commit 23036a45eb).
* Removing py::classu, because it does not seem useful enough.
* Reverting commit 6349531306 by un-commenting `const` in `def_buffer(...)`. To make this possible, `operator T const&` and `operator T const*` in `smart_holder_type_caster` need to be marked as `const` member functions.
* Adding construct() overloads for constructing smart_holder from alias unique_ptr, shared_ptr returns.
* Adding test_class_sh_factory_constructors.cpp to tests/CMakeLists.txt (fixes oversight, this should have been added long before).
* Compatibility with old clang versions (clang 3.6, 3.7 C++11).
* Cleaning up changes to existing unit tests.
* Systematically adding SMART_HOLDER_WIP tag. Removing minor UNTESTED tags (only the throw are not actually exercised, investing time there has a high cost but very little benefit).
* Splitting out smart_holder_type_casters again, into new detail/smart_holder_type_casters_inline_include.h.
* Splitting out smart_holder_init_inline_include.h.
* Adding additional new include files to CMakeLists.txt, tests/extra_python_package/test_files.py.
* clang-format cleanup of most smart_holder code.
* Adding source code comments in response to review.
* Simple micro-benchmark ("ubench") comparing runtime performance for several holders.
Tested using github.com/rwgk/pybind11_scons and Google-internal build system.
Sorry, no cmake support at the moment.
First results: https://docs.google.com/spreadsheets/d/1InapCYws2Gt-stmFf_Bwl33eOMo3aLE_gc9adveY7RU/edit#gid=0
* Breaking out number_bucket.h, adding hook for also collecting performance data for PyCLIF.
* Accounting for ubench in MANIFEST.in (simply prune, for now).
* Smarter determination of call_repetitions.
[skip ci]
* Also scaling performance data to PyCLIF.
[skip ci]
* Adding ubench/python/number_bucket.clif here for general visibility.
* Fix after rebase
* Merging detail/smart_holder_init_inline_include.h into detail/init.h.
* Renaming detail/is_smart_holder_type_caster.h -> detail/smart_holder_sfinae_hooks_only.h.
* Renaming is_smart_holder_type_caster -> type_uses_smart_holder_type_caster for clarity.
* Renaming type_caster_type_is_smart_holder_type_caster -> wrapped_type_uses_smart_holder_type_caster for clarity.
* Renaming is_smart_holder_type_caster_base_tag -> smart_holder_type_caster_base_tag for simplicity.
* Adding copyright notices and minor colateral cleanup.
* iwyu cleanup (comprehensive only for cast.h and smart_holder*.h files).
* Fixing `git rebase master` accident.
* Moving large `pragma warning` block from pybind11.h to detail/common.h.
* Fixing another `git rebase master` accident.
Ralf W. Grosse-Kunstleve