From ddb8e9f76fb8d7fb2728f3eef485e1fad6455303 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 ++++++++++++++--
 mingw_smoketests.py         |  3 +++
 setup.py                    |  4 ++++
 5 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/mingw.yml b/.github/workflows/mingw.yml
index 4d1cdcb3ac12db..cbaf8019215cdc 100644
--- a/.github/workflows/mingw.yml
+++ b/.github/workflows/mingw.yml
@@ -130,16 +130,16 @@ 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 "${pkgdir}"/* /
+
       - name: Run Smoke Test (installed)
         shell: msys2 {0}
         run: |
           export SETUPTOOLS_USE_DISTUTILS=stdlib
-          export PYTHONTZPATH="${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 19a6b2b8904526..7641b32c2d4d1b 100644
--- a/Lib/test/__main__.py
+++ b/Lib/test/__main__.py
@@ -1,2 +1,10 @@
+import os
+import sys
+
 from test.libregrtest import main
+
+if sys.platform == "win32":
+    # Enable DLL loading from PATH.
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 main()
diff --git a/Python/dynload_win.c b/Python/dynload_win.c
index 79b60be34c2d88..fcb732148a48f6 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>
@@ -223,6 +224,18 @@ 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
@@ -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
 #if !USE_UNICODE_WCHAR_CACHE
         PyMem_Free(wpathname);
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')
 
 
diff --git a/setup.py b/setup.py
index 8d2e2518af0dba..99ef3eda6c835e 100644
--- a/setup.py
+++ b/setup.py
@@ -88,6 +88,10 @@ def msys_system(command):
         return os_system(command_in_sh)
     os.system = msys_system
 
+    # set PYTHONLEGACYWINDOWSDLLLOADING to 1 to load DLLs from PATH
+    # This is needed while building core extensions of Python
+    os.environ["PYTHONLEGACYWINDOWSDLLLOADING"] = "1"
+
 CROSS_COMPILING = ("_PYTHON_HOST_PLATFORM" in os.environ)
 HOST_PLATFORM = get_platform()
 MS_WINDOWS = (HOST_PLATFORM == 'win32' or HOST_PLATFORM == 'mingw')