Fix for python load errors on Linux (#5627)

* Explicitly load libpython on Linux

Downstream loads of python modules that weren't linked to libpython would
fail to load because libraries were loaded using the RTLD_LOCAL flag.  This
adds a function that will explicitly load libpython on Linux using the
RTLD_GLOBAL flag.

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

* Fix misspelled function name

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

* Addressing PR feedback

- Updates naming and location of things.
- Adds load code to a Gem template.
- Updates error checking.

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

* Address further feedback

Removes the api function in favor of just having modules inherit off a
PythonLoader class, that way we get RAAI behavior and lifetime management
for free.

Signed-off-by: amzn-phist <52085794+amzn-phist@users.noreply.github.com>

Code/Framework/AzToolsFramework/AzToolsFramework/API/PythonLoader.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+namespace AzToolsFramework::EmbeddedPython
+{
+    // When using embedded Python, some platforms need to explicitly load the python library.
+    // For any modules that depend on 3rdParty::Python package, the AZ::Module should inherit this class.
+    class PythonLoader
+    {
+    public:
+        PythonLoader();
+        ~PythonLoader();
+
+    private:
+        void* m_embeddedLibPythonHandle{ nullptr };
+    };
+
+} // namespace AzToolsFramework::EmbeddedPython

Code/Framework/AzToolsFramework/AzToolsFramework/aztoolsframework_files.cmake

@@ -47,6 +47,7 @@ set(FILES
     API/EntityCompositionRequestBus.h
     API/EntityCompositionNotificationBus.h
     API/EditorViewportIconDisplayInterface.h
+    API/PythonLoader.h
     API/ViewPaneOptions.h
     API/ViewportEditorModeTrackerInterface.h
     Application/Ticker.h

Code/Framework/AzToolsFramework/Platform/Common/Default/AzToolsFramework/API/PythonLoader_Default.cpp

@@ -0,0 +1,20 @@
+/*
+* Copyright (c) Contributors to the Open 3D Engine Project.
+* For complete copyright and license terms please see the LICENSE at the root of this distribution.
+*
+* SPDX-License-Identifier: Apache-2.0 OR MIT
+*
+*/
+
+#include <AzToolsFramework/API/PythonLoader.h>
+
+namespace AzToolsFramework::EmbeddedPython
+{
+    PythonLoader::PythonLoader()
+    {
+    }
+
+    PythonLoader::~PythonLoader()
+    {
+    }
+}

Code/Framework/AzToolsFramework/Platform/Linux/AzToolsFramework/API/PythonLoader_Linux.cpp

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzToolsFramework/API/PythonLoader.h>
+#include <AzCore/Debug/Trace.h>
+#include <dlfcn.h>
+
+namespace AzToolsFramework::EmbeddedPython
+{
+    PythonLoader::PythonLoader()
+    {
+        constexpr char libPythonName[] = "libpython3.7m.so.1.0";
+        if (m_embeddedLibPythonHandle = dlopen(libPythonName, RTLD_NOW | RTLD_GLOBAL);
+            m_embeddedLibPythonHandle == nullptr)
+        {
+            char* err = dlerror();
+            AZ_Error("PythonLoader", false, "Failed to load %s with error: %s\n", libPythonName, err ? err : "Unknown Error");
+        }
+    }
+
+    PythonLoader::~PythonLoader()
+    {
+        if (m_embeddedLibPythonHandle)
+        {
+            dlclose(m_embeddedLibPythonHandle);
+        }
+    }
+    
+} // namespace AzToolsFramework::EmbeddedPython

Code/Framework/AzToolsFramework/Platform/Linux/platform_linux_files.cmake

@@ -7,4 +7,5 @@
 #
 
 set(FILES
+    AzToolsFramework/API/PythonLoader_Linux.cpp
 )

Code/Framework/AzToolsFramework/Platform/Mac/platform_mac_files.cmake

@@ -7,4 +7,5 @@
 #
 
 set(FILES
+    ../Common/Default/AzToolsFramework/API/PythonLoader_Default.cpp
 )

Code/Framework/AzToolsFramework/Platform/Windows/platform_windows_files.cmake

@@ -7,4 +7,5 @@
 #
 
 set(FILES
+    ../Common/Default/AzToolsFramework/API/PythonLoader_Default.cpp
 )

Gems/Atom/Tools/AtomToolsFramework/Code/Source/AtomToolsFrameworkModule.h

@@ -9,11 +9,13 @@
 #pragma once
 
 #include <AzCore/Module/Module.h>
+#include <AzToolsFramework/API/PythonLoader.h>
 
 namespace AtomToolsFramework
 {
     class AtomToolsFrameworkModule
         : public AZ::Module
+        , public AzToolsFramework::EmbeddedPython::PythonLoader
     {
     public:
         AZ_RTTI(AtomToolsFrameworkModule, "{B58B7CA8-98C9-4DC8-8607-E094989BBBE2}", AZ::Module);

Gems/EditorPythonBindings/Code/Source/EditorPythonBindingsModule.cpp

@@ -9,6 +9,8 @@
 #include <AzCore/Memory/SystemAllocator.h>
 #include <AzCore/Module/Module.h>
 
+#include <AzToolsFramework/API/PythonLoader.h>
+
 #include <PythonSystemComponent.h>
 #include <PythonReflectionComponent.h>
 #include <PythonMarshalComponent.h>
@@ -18,6 +20,7 @@ namespace EditorPythonBindings
 {
     class EditorPythonBindingsModule
         : public AZ::Module
+        , public AzToolsFramework::EmbeddedPython::PythonLoader
     {
     public:
         AZ_RTTI(EditorPythonBindingsModule, "{851B9E35-4FD5-49B1-8207-E40D4BBA36CC}", AZ::Module);

Gems/PythonAssetBuilder/Code/Source/PythonAssetBuilderModule.cpp

@@ -9,12 +9,15 @@
 #include <AzCore/Memory/SystemAllocator.h>
 #include <AzCore/Module/Module.h>
 
+#include <AzToolsFramework/API/PythonLoader.h>
+
 #include <PythonAssetBuilderSystemComponent.h>
 
 namespace PythonAssetBuilder
 {
     class PythonAssetBuilderModule
         : public AZ::Module
+        , public AzToolsFramework::EmbeddedPython::PythonLoader
     {
     public:
         AZ_RTTI(PythonAssetBuilderModule, "{35C9457E-54C2-474C-AEBE-5A70CC1D435D}", AZ::Module);

Templates/PythonToolGem/Template/Code/Source/${Name}EditorModule.cpp

@@ -10,6 +10,7 @@
 
 #include <${Name}ModuleInterface.h>
 #include <${Name}EditorSystemComponent.h>
+#include <AzToolsFramework/API/PythonLoader.h>
 
 void Init${SanitizedCppName}Resources()
 {
@@ -21,6 +22,7 @@ namespace ${SanitizedCppName}
 {
     class ${SanitizedCppName}EditorModule
         : public ${SanitizedCppName}ModuleInterface
+        , public AzToolsFramework::EmbeddedPython::PythonLoader
     {
     public:
         AZ_RTTI(${SanitizedCppName}EditorModule, "${ModuleClassId}", ${SanitizedCppName}ModuleInterface);