From 480b3a1ff99558ce4bec2c61a792a47ee43637e7 Mon Sep 17 00:00:00 2001
From: Naveen M K <naveen521kk@gmail.com>
Date: Sat, 5 Aug 2023 14:10:27 +0530
Subject: [PATCH 099/N] Search DLLs only on paths added using
 `add_dll_directory()`.

This is the default behavior on upstream Python. We previously
reverted this behavior because it broke some use cases.

The old behavior can be restored by setting the environment variable
PYTHONLEGACYWINDOWSDLLLOADING to 1.

Fixes https://github.com/msys2-contrib/cpython-mingw/issues/48
Also fixes https://github.com/msys2-contrib/cpython-mingw/issues/141

Signed-off-by: Naveen M K <naveen521kk@gmail.com>
---
 Lib/test/__main__.py                   |  8 ++++++++
 Python/dynload_win.c                   | 16 ++++++++++++++--
 Tools/build/check_extension_modules.py |  4 ++++
 mingw_smoketests.py                    |  3 +++
 4 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/Lib/test/__main__.py b/Lib/test/__main__.py
index 82b50ad..25bac39 100644
--- a/Lib/test/__main__.py
+++ b/Lib/test/__main__.py
@@ -1,2 +1,10 @@
+import os
+import sys
+
 from test.libregrtest.main import main
+
+if sys.platform == "win32":
+    # Enable DLL loading from PATH.
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 main(_add_python_opts=True)
diff --git a/Python/dynload_win.c b/Python/dynload_win.c
index 1f90e21..db79687 100644
--- a/Python/dynload_win.c
+++ b/Python/dynload_win.c
@@ -4,6 +4,7 @@
 #include "Python.h"
 #include "pycore_fileutils.h"     // _Py_add_relfile()
 #include "pycore_pystate.h"       // _PyInterpreterState_GET()
+#include "pycore_initconfig.h"
 
 #ifdef HAVE_DIRECT_H
 #include <direct.h>
@@ -225,6 +226,18 @@ dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,
     dl_funcptr p;
     char funcname[258], *import_python;
 
+    int use_legacy = 0;
+    DWORD load_library_flags = 0;
+
+    _Py_get_env_flag(1, &use_legacy, "PYTHONLEGACYWINDOWSDLLLOADING");
+
+    if (use_legacy) {
+        load_library_flags = LOAD_WITH_ALTERED_SEARCH_PATH;
+    } else {
+        load_library_flags = LOAD_LIBRARY_SEARCH_DEFAULT_DIRS |
+                              LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR;
+    }
+
 #ifdef _MSC_VER
     _Py_CheckPython3(); 
 #endif /* _MSC_VER */
@@ -249,8 +262,7 @@ dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,
            AddDllDirectory function. We add SEARCH_DLL_LOAD_DIR to
            ensure DLLs adjacent to the PYD are preferred. */
         Py_BEGIN_ALLOW_THREADS
-        hDLL = LoadLibraryExW(wpathname, NULL,
-                              LOAD_WITH_ALTERED_SEARCH_PATH);
+        hDLL = LoadLibraryExW(wpathname, NULL, load_library_flags);
         Py_END_ALLOW_THREADS
         PyMem_Free(wpathname);
 
diff --git a/Tools/build/check_extension_modules.py b/Tools/build/check_extension_modules.py
index aa1ade7..7ded0f4 100644
--- a/Tools/build/check_extension_modules.py
+++ b/Tools/build/check_extension_modules.py
@@ -61,6 +61,10 @@ WINDOWS_MODULES = {
     "winsound",
 }
 
+if sys.platform == "win32":
+    # Enable DLL loading from PATH.
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 
 logger = logging.getLogger(__name__)
 
diff --git a/mingw_smoketests.py b/mingw_smoketests.py
index 516005c..ca1f652 100644
--- a/mingw_smoketests.py
+++ b/mingw_smoketests.py
@@ -34,6 +34,9 @@ if os.environ.get("MSYSTEM", ""):
 else:
     SEP = "\\"
 
+if sysconfig.is_python_build():
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 _UCRT = sysconfig.get_platform() not in ('mingw_x86_64', 'mingw_i686')
 
 
