From cd2927084b47627236aad65067d72d8596e2c74d 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] 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>
---
 .github/workflows/mingw.yml            | 10 +++++-----
 Lib/test/__main__.py                   |  8 ++++++++
 Python/dynload_win.c                   | 16 ++++++++++++++--
 Tools/build/check_extension_modules.py |  4 ++++
 mingw_smoketests.py                    |  3 +++
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/mingw.yml b/.github/workflows/mingw.yml
index 6445b6bf9f2c9b..f0a0d92429d9c1 100644
--- a/.github/workflows/mingw.yml
+++ b/.github/workflows/mingw.yml
@@ -126,15 +126,15 @@ jobs:
           cp "${pkgdir}${MINGW_PREFIX}"/bin/idle3 "${pkgdir}${MINGW_PREFIX}"/bin/idle
           cp "${pkgdir}${MINGW_PREFIX}"/bin/pydoc3 "${pkgdir}${MINGW_PREFIX}"/bin/pydoc
 
+          # copy to /
+          cp -rf "${pkgdir}"/* /
+
       - name: Run Smoke Test (installed)
         shell: msys2 {0}
         run: |
-          export PYTHONTZPATH="${MINGW_PREFIX}/share/zoneinfo"
           SMOKETESTS="$(pwd)/mingw_smoketests.py"
-          cd _build
-          cd python_pkgdir/${MINGW_PREFIX}/bin
-          ./python.exe "$SMOKETESTS"
-          MSYSTEM= ./python.exe "$SMOKETESTS"
+          ${MINGW_PREFIX}/bin/python.exe "$SMOKETESTS"
+          MSYSTEM= ${MINGW_PREFIX}/bin/python.exe "$SMOKETESTS"
 
       - name: Compress
         if: always()
diff --git a/Lib/test/__main__.py b/Lib/test/__main__.py
index 82b50ad2c6e777..25bac39e24af20 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 1f90e21a77fecc..db7968742b2228 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 59239c62e2ef34..6810b3b565bc4e 100644
--- a/Tools/build/check_extension_modules.py
+++ b/Tools/build/check_extension_modules.py
@@ -60,6 +60,10 @@
     "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 516005c9b3eeb6..ca1f652caeec27 100644
--- a/mingw_smoketests.py
+++ b/mingw_smoketests.py
@@ -34,6 +34,9 @@
 else:
     SEP = "\\"
 
+if sysconfig.is_python_build():
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 _UCRT = sysconfig.get_platform() not in ('mingw_x86_64', 'mingw_i686')