Revert "bpo-39401: Avoid unsafe DLL load on Windows 7 and earlier (pythonGH-18231)"

This reverts commit 6a65eba.

Author: kuba2k2

PC/getpathp.c

@@ -90,7 +90,7 @@
 #endif
 
 #include <windows.h>
-#include <pathcch.h>
+#include <shlwapi.h>
 
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>
@@ -249,14 +249,42 @@ ismodule(wchar_t *filename, int update_filename)
    stuff as fits will be appended.
 */
 
+static int _PathCchCombineEx_Initialized = 0;
+typedef HRESULT(__stdcall *PPathCchCombineEx) (PWSTR pszPathOut, size_t cchPathOut,
+                                               PCWSTR pszPathIn, PCWSTR pszMore,
+                                               unsigned long dwFlags);
+static PPathCchCombineEx _PathCchCombineEx;
+
 static void
 join(wchar_t *buffer, const wchar_t *stuff)
 {
-    if (FAILED(PathCchCombineEx(buffer, MAXPATHLEN+1, buffer, stuff, 0))) {
-        Py_FatalError("buffer overflow in getpathp.c's join()");
+    if (_PathCchCombineEx_Initialized == 0) {
+        HMODULE pathapi = LoadLibraryW(L"api-ms-win-core-path-l1-1-0.dll");
+        if (pathapi) {
+            _PathCchCombineEx = (PPathCchCombineEx)GetProcAddress(pathapi, "PathCchCombineEx");
+        }
+        else {
+            _PathCchCombineEx = NULL;
+        }
+        _PathCchCombineEx_Initialized = 1;
+    }
+
+    if (_PathCchCombineEx) {
+        if (FAILED(_PathCchCombineEx(buffer, MAXPATHLEN+1, buffer, stuff, 0))) {
+            Py_FatalError("buffer overflow in getpathp.c's join()");
+        }
+    } else {
+        if (!PathCombineW(buffer, buffer, stuff)) {
+            Py_FatalError("buffer overflow in getpathp.c's join()");
+        }
     }
 }
 
+static int _PathCchCanonicalizeEx_Initialized = 0;
+typedef HRESULT(__stdcall *PPathCchCanonicalizeEx) (PWSTR pszPathOut, size_t cchPathOut,
+    PCWSTR pszPathIn, unsigned long dwFlags);
+static PPathCchCanonicalizeEx _PathCchCanonicalizeEx;
+
 /* Call PathCchCanonicalizeEx(path): remove navigation elements such as "."
    and ".." to produce a direct, well-formed path. */
 static PyStatus
@@ -266,8 +294,26 @@ canonicalize(wchar_t *buffer, const wchar_t *path)
         return _PyStatus_NO_MEMORY();
     }
 
-    if (FAILED(PathCchCanonicalizeEx(buffer, MAXPATHLEN + 1, path, 0))) {
-        return INIT_ERR_BUFFER_OVERFLOW();
+    if (_PathCchCanonicalizeEx_Initialized == 0) {
+        HMODULE pathapi = LoadLibraryW(L"api-ms-win-core-path-l1-1-0.dll");
+        if (pathapi) {
+            _PathCchCanonicalizeEx = (PPathCchCanonicalizeEx)GetProcAddress(pathapi, "PathCchCanonicalizeEx");
+        }
+        else {
+            _PathCchCanonicalizeEx = NULL;
+        }
+        _PathCchCanonicalizeEx_Initialized = 1;
+    }
+
+    if (_PathCchCanonicalizeEx) {
+        if (FAILED(_PathCchCanonicalizeEx(buffer, MAXPATHLEN + 1, path, 0))) {
+            return INIT_ERR_BUFFER_OVERFLOW();
+        }
+    }
+    else {
+        if (!PathCanonicalizeW(buffer, path)) {
+            return INIT_ERR_BUFFER_OVERFLOW();
+        }
     }
     return _PyStatus_OK();
 }

PCbuild/pythoncore.vcxproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup Label="ProjectConfigurations">
     <ProjectConfiguration Include="Debug|ARM">
@@ -106,7 +106,7 @@
       <PreprocessorDefinitions Condition="$(IncludeExternals)">_Py_HAVE_ZLIB;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
     <Link>
-      <AdditionalDependencies>version.lib;ws2_32.lib;pathcch.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <AdditionalDependencies>version.lib;shlwapi.lib;ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>