Test: Default Alias in Base Class

include/pybind11/detail/internals.h

@@ -114,7 +114,7 @@ inline void tls_replace_value(PYBIND11_TLS_KEY_REF key, void *value) {
 // libstdc++, this doesn't happen: equality and the type_index hash are based on the type name,
 // which works.  If not under a known-good stl, provide our own name-based hash and equality
 // functions that use the type name.
-#if defined(__GLIBCXX__)
+#if 0
 inline bool same_type(const std::type_info &lhs, const std::type_info &rhs) { return lhs == rhs; }
 using type_hash = std::hash<std::type_index>;
 using type_equal_to = std::equal_to<std::type_index>;

include/pybind11/pybind11.h

@@ -18,6 +18,7 @@
 
 #include <cstdlib>
 #include <cstring>
+#include <iostream>
 #include <memory>
 #include <new>
 #include <string>
@@ -221,10 +222,12 @@ class cpp_function : public function {
 
         /* Dispatch code which converts function arguments and performs the actual function call */
         rec->impl = [](function_call &call) -> handle {
+            std::cout << "in rec->impl" << std::endl;
             cast_in args_converter;
 
             /* Try to cast the function arguments into the C++ domain */
             if (!args_converter.load_args(call)) {
+                std::cout << ".. returning PYBIND11_TRY_NEXT_OVERLOAD" << std::endl;
                 return PYBIND11_TRY_NEXT_OVERLOAD;
             }
 
@@ -247,11 +250,18 @@ class cpp_function : public function {
             handle result
                 = cast_out::cast(std::move(args_converter).template call<Return, Guard>(cap->f),
                                  policy,
-                                 call.parent);
+                                 call.parent); // FIXME this seems to fail to detect identical
+                                               // return types with all compilers but GCC
+
+            std::cout << ".. after cast_out::cast - result=" << result.ptr() << " "
+                      << (result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) << std::endl;
 
             /* Invoke call policy post-call hook */
             process_attributes<Extra...>::postcall(call, result);
 
+            std::cout << ".. after postcall - result=" << result.ptr() << " "
+                      << (result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) << std::endl;
+
             return result;
         };
 
@@ -705,6 +715,7 @@ class cpp_function : public function {
         }
 
         try {
+            std::cout << "Starting two-pass matching..." << std::endl;
             // We do this in two passes: in the first pass, we load arguments with `convert=false`;
             // in the second, we allow conversion (except for arguments with an explicit
             // py::arg().noconvert()).  This lets us prefer calls without conversion, with
@@ -761,6 +772,7 @@ class cpp_function : public function {
                 size_t args_copied = 0;
 
                 // 0. Inject new-style `self` argument
+                std::cout << "0. Inject new-style `self` argument" << std::endl;
                 if (func.is_new_style_constructor) {
                     // The `value` may have been preallocated by an old-style `__init__`
                     // if it was a preceding candidate for overload resolution.
@@ -775,6 +787,7 @@ class cpp_function : public function {
                 }
 
                 // 1. Copy any position arguments given.
+                std::cout << "1. Copy any position arguments given." << std::endl;
                 bool bad_arg = false;
                 for (; args_copied < args_to_copy; ++args_copied) {
                     const argument_record *arg_rec
@@ -805,6 +818,8 @@ class cpp_function : public function {
                 dict kwargs = reinterpret_borrow<dict>(kwargs_in);
 
                 // 1.5. Fill in any missing pos_only args from defaults if they exist
+                std::cout << "1.5. Fill in any missing pos_only args from defaults if they exist"
+                          << std::endl;
                 if (args_copied < func.nargs_pos_only) {
                     for (; args_copied < func.nargs_pos_only; ++args_copied) {
                         const auto &arg_rec = func.args[args_copied];
@@ -827,6 +842,9 @@ class cpp_function : public function {
                 }
 
                 // 2. Check kwargs and, failing that, defaults that may help complete the list
+                std::cout << "2. Check kwargs and, failing that, defaults that may help complete "
+                             "the list"
+                          << std::endl;
                 if (args_copied < num_args) {
                     bool copied_kwargs = false;
 
@@ -876,11 +894,16 @@ class cpp_function : public function {
                 }
 
                 // 3. Check everything was consumed (unless we have a kwargs arg)
+                std::cout << "3. Check everything was consumed (unless we have a kwargs arg)"
+                          << std::endl;
                 if (kwargs && !kwargs.empty() && !func.has_kwargs) {
                     continue; // Unconsumed kwargs, but no py::kwargs argument to accept them
                 }
 
                 // 4a. If we have a py::args argument, create a new tuple with leftovers
+                std::cout
+                    << "4a. If we have a py::args argument, create a new tuple with leftovers"
+                    << std::endl;
                 if (func.has_args) {
                     tuple extra_args;
                     if (args_to_copy == 0) {
@@ -906,6 +929,8 @@ class cpp_function : public function {
                 }
 
                 // 4b. If we have a py::kwargs, pass on any remaining kwargs
+                std::cout << "4b. If we have a py::kwargs, pass on any remaining kwargs"
+                          << std::endl;
                 if (func.has_kwargs) {
                     if (!kwargs.ptr()) {
                         kwargs = dict(); // If we didn't get one, send an empty one
@@ -917,7 +942,10 @@ class cpp_function : public function {
 
 // 5. Put everything in a vector.  Not technically step 5, we've been building it
 // in `call.args` all along.
-#if defined(PYBIND11_DETAILED_ERROR_MESSAGES)
+#if 1
+                std::cout << "5. Put everything in a vector.  Not technically step 5, we've been "
+                             "building it in `call.args` all along."
+                          << std::endl;
                 if (call.args.size() != func.nargs || call.args_convert.size() != func.nargs) {
                     pybind11_fail("Internal error: function call dispatcher inserted wrong number "
                                   "of arguments!");
@@ -934,18 +962,24 @@ class cpp_function : public function {
                 }
 
                 // 6. Call the function.
+                std::cout << "6. Call the function." << std::endl;
                 try {
                     loader_life_support guard{};
-                    result = func.impl(call);
+                    result = func.impl(
+                        call); // FIXME looks like this fails to match identical return types
                 } catch (reference_cast_error &) {
+                    std::cout << ".. catch (reference_cast_error &)" << std::endl;
                     result = PYBIND11_TRY_NEXT_OVERLOAD;
                 }
 
                 if (result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD) {
+                    std::cout << ".. result.ptr() != PYBIND11_TRY_NEXT_OVERLOAD -> break"
+                              << std::endl;
                     break;
                 }
 
                 if (overloaded) {
+                    std::cout << ".. overloaded" << std::endl;
                     // The (overloaded) call failed; if the call has at least one argument that
                     // permits conversion (i.e. it hasn't been explicitly specified `.noconvert()`)
                     // then add this call to the list of second pass overloads to try.
@@ -964,6 +998,9 @@ class cpp_function : public function {
             if (overloaded && !second_pass.empty() && result.ptr() == PYBIND11_TRY_NEXT_OVERLOAD) {
                 // The no-conversion pass finished without success, try again with conversion
                 // allowed
+                std::cout << "The no-conversion pass finished without success, try again with "
+                             "conversion allowed"
+                          << std::endl;
                 for (auto &call : second_pass) {
                     try {
                         loader_life_support guard{};

tests/CMakeLists.txt

@@ -153,6 +153,7 @@ set(PYBIND11_TEST_FILES
     test_stl
     test_stl_binders
     test_tagbased_polymorphic
+    test_template_alias_base
     test_thread
     test_union
     test_virtual_functions)
@@ -521,8 +522,8 @@ set(PYBIND11_TEST_PREFIX_COMMAND
 # A single command to compile and run the tests
 add_custom_target(
   pytest
-  COMMAND ${PYBIND11_TEST_PREFIX_COMMAND} ${PYTHON_EXECUTABLE} -m pytest
-          ${PYBIND11_ABS_PYTEST_FILES}
+  COMMAND ${PYBIND11_TEST_PREFIX_COMMAND} ${PYTHON_EXECUTABLE} -m pytest -s -vvvv
+          "${CMAKE_CURRENT_SOURCE_DIR}/test_template_alias_base.py"
   DEPENDS ${test_targets}
   WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
   USES_TERMINAL)

tests/test_template_alias_base.cpp

@@ -0,0 +1,28 @@
+#include "pybind11_tests.h"
+
+#include <iostream>
+#include <memory>
+
+template <class T>
+using DefaultAllocator = std::allocator<T>;
+
+template <template <class> class Allocator = DefaultAllocator>
+struct Base {};
+
+template <template <class> class Allocator = DefaultAllocator>
+struct S : public Base<Allocator> {};
+
+// this returns S<DefaultAllocator> even though we register
+// the type S<std::allocator>
+// MSVC and Clang on Windows failed here to detect the registered type
+S<> make_S() {
+    std::cout << "in make_S()" << std::endl;
+    return S<>{};
+}
+
+TEST_SUBMODULE(template_alias_base, m) {
+    py::class_<Base<std::allocator>>(m, "B_std").def(py::init());
+    py::class_<S<std::allocator>, Base<std::allocator>>(m, "S_std").def(py::init());
+
+    m.def("make_S", &make_S);
+}

tests/test_template_alias_base.py

@@ -0,0 +1,11 @@
+from pybind11_tests import template_alias_base as m
+
+
+def test_can_create_variable():
+    v = m.S_std()
+    print(v)
+
+
+def test_can_return_variable():
+    v = m.make_S()
+    print(v)