Solve delay load import issues on windows.

Author: viferga

source/dynlink/include/dynlink/dynlink_type.h

@@ -72,6 +72,20 @@ typedef void (*dynlink_symbol_addr)(void);		  /**< Function pointer referring to
 \
 	} while (0)
 
+#define dynlink_symbol_uncast_type(fn, type, result) \
+	do \
+	{ \
+		union \
+		{ \
+			type ptr; \
+			dynlink_symbol_addr fn; \
+		} cast; \
+\
+		cast.fn = (fn); \
+		(result) = (type)cast.ptr; \
+\
+	} while (0)
+
 #ifdef __cplusplus
 }
 #endif

source/loaders/py_loader/CMakeLists.txt

@@ -9,46 +9,73 @@ endif()
 
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
 	set(Python3_FIND_ABI "ON" "ANY" "ANY")
-	find_package(Python3 COMPONENTS Development)
+	find_package(Python3 COMPONENTS Interpreter Development)
 
 	# Fallback to release if not found
 	if(NOT Python3_Development_FOUND)
 		set(Python3_FIND_ABI)
-		find_package(Python3 COMPONENTS Development REQUIRED)
+		find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
 	endif()
 else()
-	find_package(Python3 COMPONENTS Development REQUIRED)
+	find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
+endif()
+
+# Select the proper library
+if(NOT Python3_LIBRARY AND Python3_LIBRARIES)
+	# Go through the list and handle keyword-separated structure
+	set(index 0)
+	list(LENGTH Python3_LIBRARIES lib_len)
+	while(index LESS lib_len)
+		list(GET Python3_LIBRARIES ${index} item)
+
+		# Check if it's a keyword (debug/optimized)
+		if(item STREQUAL "debug" OR item STREQUAL "optimized" OR item STREQUAL "general")
+			set(keyword ${item})
+			math(EXPR next "${index} + 1")
+			list(GET Python3_LIBRARIES ${next} lib_path)
+
+			# Match the right keyword
+			if((CMAKE_BUILD_TYPE STREQUAL "Debug" AND keyword STREQUAL "debug") OR
+			   (NOT CMAKE_BUILD_TYPE STREQUAL "Debug" AND keyword STREQUAL "optimized") OR
+			   (keyword STREQUAL "general"))  # general applies to all configs
+				set(Python3_LIBRARY ${lib_path})
+			endif()
+
+			math(EXPR index "${index} + 2")  # Skip keyword and path
+		else()
+			# Plain list without keywords (single-config or fallback)
+			set(Python3_LIBRARY ${item})
+			math(EXPR index "${index} + 1")
+		endif()
+	endwhile()
 endif()
 
 # Copy Python DLL into project output directory
 # TODO: https://cmake.org/cmake/help/latest/command/file.html#get-runtime-dependencies
 # TODO: https://gist.github.com/micahsnyder/5d98ac8548b429309ec5a35bca9366da
 include(Portability)
 
-if(PROJECT_OS_FAMILY STREQUAL win32 AND Python3_LIBRARIES AND Python3_ROOT_DIR AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug")
-	foreach(library ${Python3_LIBRARIES})
-		if(${library} MATCHES "[^_d][.]lib$")
-			# Get the library path with dll suffix
-			string(REGEX REPLACE "[.]lib$" ".dll" LIB_PATH ${library})
-			# Get the library name
-			get_filename_component(LIB_NAME "${LIB_PATH}" NAME)
-			# Find the library in the Python3 root path
-			find_file(Python3_LIBRARY_NAME_PATH ${LIB_NAME}
-				PATHS ${Python3_ROOT_DIR}
-				NO_DEFAULT_PATH
-			)
-			if(Python3_LIBRARY_NAME_PATH)
-				break()
-			endif()
-		endif()
-	endforeach()
+if(PROJECT_OS_FAMILY STREQUAL win32 AND Python3_LIBRARY)
+	# Get the library path with dll suffix
+	string(REGEX REPLACE "[.]lib$" ".dll" LIB_PATH "${Python3_LIBRARY}")
+	# Get the library name
+	get_filename_component(LIB_NAME "${LIB_PATH}" NAME)
+	# Get the python root folder
+	if(NOT Python3_ROOT_DIR)
+		get_filename_component(Python3_ROOT_DIR "${Python3_EXECUTABLE}" DIRECTORY)
+	endif()
+	# Find the library in the Python3 root path
+	find_file(Python3_LIBRARY_NAME_PATH "${LIB_NAME}"
+		PATHS "${Python3_ROOT_DIR}"
+		NO_DEFAULT_PATH
+	)
+	# Copy the DLL to the output directory
+	execute_process(COMMAND ${CMAKE_COMMAND} -E make_directory "${PROJECT_OUTPUT_DIR}")
+	file(COPY "${Python3_LIBRARY_NAME_PATH}" DESTINATION "${PROJECT_OUTPUT_DIR}")
 endif()
 
-if(Python3_LIBRARY_NAME_PATH)
-	execute_process(COMMAND ${CMAKE_COMMAND} -E make_directory ${PROJECT_OUTPUT_DIR})
-	file(COPY "${Python3_LIBRARY_NAME_PATH}" DESTINATION ${PROJECT_OUTPUT_DIR})
-else()
-	set(Python3_LIBRARY_NAME_PATH "${Python3_LIBRARIES}")
+if(NOT Python3_LIBRARY_NAME_PATH)
+	set(Python3_LIBRARY_NAME_PATH "${Python3_LIBRARY}")
 endif()
 
 #
@@ -91,6 +118,7 @@ set(headers
 	${include_path}/py_loader_port.h
 	${include_path}/py_loader_threading.h
 	${include_path}/py_loader_dict.h
+	${include_path}/py_loader_symbol_fallback.h
 )
 
 set(sources
@@ -174,7 +202,7 @@ target_link_libraries(${target}
 	${META_PROJECT_NAME}::metacall # MetaCall library
 
 	# Delay load for MSVC
-	$<$<CXX_COMPILER_ID:MSVC>:${Python3_LIBRARIES}> # Python library
+	$<$<CXX_COMPILER_ID:MSVC>:${Python3_LIBRARY}> # Python library
 	$<$<CXX_COMPILER_ID:MSVC>:delayimp>
 
 	PUBLIC

source/loaders/py_loader/include/py_loader/py_loader_symbol_fallback.h

@@ -0,0 +1,60 @@
+/*
+ *	Loader Library by Parra Studios
+ *	A plugin for loading python code at run-time into a process.
+ *
+ *	Copyright (C) 2016 - 2025 Vicente Eduardo Ferrer Garcia <[email protected]>
+ *
+ *	Licensed under the Apache License, Version 2.0 (the "License");
+ *	you may not use this file except in compliance with the License.
+ *	You may obtain a copy of the License at
+ *
+ *		http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *	Unless required by applicable law or agreed to in writing, software
+ *	distributed under the License is distributed on an "AS IS" BASIS,
+ *	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *	See the License for the specific language governing permissions and
+ *	limitations under the License.
+ *
+ */
+
+#ifndef PY_LOADER_SYMBOL_FALLBACK_H
+#define PY_LOADER_SYMBOL_FALLBACK_H 1
+
+#include <py_loader/py_loader_api.h>
+
+#include <dynlink/dynlink.h>
+
+#include <Python.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+PY_LOADER_NO_EXPORT int py_loader_symbol_fallback_initialize(dynlink py_library);
+
+#if defined(_WIN32) && defined(_MSC_VER)
+	#undef PyBool_Check
+PY_LOADER_NO_EXPORT int PyBool_Check(const PyObject *ob);
+	#undef PyFloat_Check
+PY_LOADER_NO_EXPORT int PyFloat_Check(const PyObject *ob);
+	#undef PyCapsule_CheckExact
+PY_LOADER_NO_EXPORT int PyCapsule_CheckExact(const PyObject *ob);
+	#undef PyFunction_Check
+PY_LOADER_NO_EXPORT int PyFunction_Check(const PyObject *ob);
+	#undef PyCFunction_Check
+PY_LOADER_NO_EXPORT int PyCFunction_Check(const PyObject *ob);
+	#undef PyModule_Check
+PY_LOADER_NO_EXPORT int PyModule_Check(const PyObject *ob);
+#endif
+
+PY_LOADER_NO_EXPORT PyObject *Py_NonePtr(void);
+PY_LOADER_NO_EXPORT PyObject *Py_ReturnNone(void);
+PY_LOADER_NO_EXPORT PyObject *Py_ReturnFalse(void);
+PY_LOADER_NO_EXPORT PyObject *Py_ReturnTrue(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PY_LOADER_SYMBOL_FALLBACK_H */

source/loaders/py_loader/source/py_loader_impl.c

@@ -21,6 +21,7 @@
 #include <py_loader/py_loader_dict.h>
 #include <py_loader/py_loader_impl.h>
 #include <py_loader/py_loader_port.h>
+#include <py_loader/py_loader_symbol_fallback.h>
 #include <py_loader/py_loader_threading.h>
 
 #include <loader/loader.h>
@@ -280,7 +281,7 @@ PyObject *py_loader_impl_capsule_new_null(void)
 	/* We want to create a new capsule with contents set to NULL, but PyCapsule
 	* does not allow that, instead we are going to identify our NULL capsule with
 	* this configuration (setting the capsule to Py_None) */
-	return PyCapsule_New(Py_None, py_loader_capsule_null_id, NULL);
+	return PyCapsule_New((void *)Py_NonePtr(), py_loader_capsule_null_id, NULL);
 }
 
 void py_loader_impl_value_invoke_state_finalize(value v, void *data)
@@ -918,7 +919,7 @@ type_id py_loader_impl_capi_to_value_type(loader_impl impl, PyObject *obj)
 	{
 		return TYPE_FUNCTION;
 	}
-	else if (obj == Py_None)
+	else if (obj == Py_NonePtr())
 	{
 		return TYPE_NULL;
 	}
@@ -1146,7 +1147,7 @@ value py_loader_impl_capi_to_value(loader_impl impl, PyObject *obj, type_id id)
 		const char *name = PyCapsule_GetName(obj);
 		void *ptr = PyCapsule_GetPointer(obj, name);
 
-		if (ptr == Py_None && name == py_loader_capsule_null_id)
+		if (ptr == Py_NonePtr() && name == py_loader_capsule_null_id)
 		{
 			v = value_create_ptr(NULL);
 		}
@@ -1293,7 +1294,7 @@ value py_loader_impl_capi_to_value(loader_impl impl, PyObject *obj, type_id id)
 	{
 		PyObject *tb = PyException_GetTraceback(obj);
 
-		v = py_loader_impl_error_value_from_exception(loader_impl_get(impl), (PyObject *)Py_TYPE(obj), obj, tb ? tb : Py_None);
+		v = py_loader_impl_error_value_from_exception(loader_impl_get(impl), (PyObject *)Py_TYPE(obj), obj, tb ? tb : Py_NonePtr());
 
 		Py_XDECREF(tb);
 	}
@@ -2670,6 +2671,12 @@ loader_impl_data py_loader_impl_initialize(loader_impl impl, configuration confi
 #endif
 	}
 
+	/* Initialize symbol fallback */
+	if (py_loader_symbol_fallback_initialize(loader_impl_dependency(impl, "python")) != 0)
+	{
+		goto error_init_py;
+	}
+
 	/* Initialize threading */
 	py_loader_thread_initialize(host);