Clean up manifest patch tool

src/patch_java_manifest_for_utf8.cc

@@ -20,71 +20,72 @@
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
+// This program patches the app manifest of the java.exe launcher to force its
+// active code page to UTF-8. This is necessary because the launcher sets
+// sun.jnu.encoding to the system code page, which by default is a legacy
+// code page such as Cp1252 on Windows.
 int wmain(int argc, wchar_t *argv[]) {
   if (argc != 2) {
-    wprintf(L"Usage: %s <filename>\n", argv[0]);
+    fwprintf(stderr, L"Usage: %ls <filename>\n", argv[0]);
     return 1;
   }
 
+  // Read the app manifest (aka side-by-side or fusion manifest) from the
+  // executable, which requires loading it as a "module".
   HMODULE exe = LoadLibraryExW(argv[1], nullptr, LOAD_LIBRARY_AS_DATAFILE);
   if (!exe) {
-    wprintf(L"Error loading file: %s\n", argv[1]);
+    fwprintf(stderr, L"Error loading file %ls\n", argv[1]);
     return 1;
   }
-
-  HRSRC manifestResource = FindResourceA(exe, MAKEINTRESOURCE(1), RT_MANIFEST);
-  if (!manifestResource) {
+  HRSRC manifest_resource = FindResourceA(exe, MAKEINTRESOURCE(1), RT_MANIFEST);
+  if (!manifest_resource) {
     fwprintf(stderr, L"Resource not found.\n");
     return 1;
   }
-
-  HGLOBAL manifestHandle = LoadResource(exe, manifestResource);
-  if (!manifestHandle) {
+  HGLOBAL manifest_handle = LoadResource(exe, manifest_resource);
+  if (!manifest_handle) {
     fwprintf(stderr, L"Error loading resource.\n");
     return 1;
   }
-  LPVOID manifestData = LockResource(manifestHandle);
-  if (!manifestData) {
+  LPVOID manifest_data = LockResource(manifest_handle);
+  if (!manifest_data) {
     fwprintf(stderr, L"Error locking resource.\n");
     return 1;
   }
-  DWORD manifestLen = SizeofResource(exe, manifestResource);
-
-  std::string manifest((char *) manifestData, manifestLen);
-  fwprintf(stderr, L"Manifest data: %s\n", manifest.c_str());
-
-  UnlockResource(manifestHandle);
-  FreeResource(manifestHandle);
+  DWORD manifest_len = SizeofResource(exe, manifest_resource);
+  std::string manifest((char *) manifest_data, manifest_len);
+  UnlockResource(manifest_handle);
+  FreeResource(manifest_handle);
+  FreeLibrary(exe);
 
-  std::size_t insertPos = manifest.find("</asmv3:windowsSettings>");
-  if (insertPos == std::wstring::npos) {
-    fwprintf(stderr, L"End tag not found.\n");
+  // Insert the activeCodePage element into the manifest at the end of the
+  // windowsSettings element.
+  // https://github.com/openjdk/jdk/blob/29882bfe7b7e76446a96862cd0a5e81c7e054415/src/java.base/windows/native/launcher/java.manifest#L43
+  std::size_t insert_pos = manifest.find("</asmv3:windowsSettings>");
+  if (insert_pos == std::wstring::npos) {
+    fwprintf(stderr, L"End tag not found in manifest:\n%s", manifest.c_str());
     return 1;
   }
-  std::string newManifest = manifest.substr(0, insertPos) +
+  std::string new_manifest = manifest.substr(0, insert_pos) +
       "<activeCodePage xmlns=\"http://schemas.microsoft.com/SMI/2019/WindowsSettings\">UTF-8</activeCodePage>" +
-      manifest.substr(insertPos);
+      manifest.substr(insert_pos);
 
-  fwprintf(stderr, L"Modified manifest data: %ls\n", newManifest.c_str());
-
-  HANDLE updateHandle = BeginUpdateResourceW(argv[1], false);
-  if (!updateHandle) {
+  // Write back the modified app manifest.
+  HANDLE update_handle = BeginUpdateResourceW(argv[1], false);
+  if (!update_handle) {
     fwprintf(stderr, L"Error opening file for update.\n");
     return 1;
   }
-
-  // Update the resource in the file
-  if (!UpdateResourceW(updateHandle,
-                       MAKEINTRESOURCEW(1),
-                       MAKEINTRESOURCEW(24),
+  if (!UpdateResourceA(update_handle,
+                       MAKEINTRESOURCE(1),
+                       RT_MANIFEST,
                        MAKELANGID(LANG_NEUTRAL, SUBLANG_NEUTRAL),
-                       (char *) newManifest.c_str(),
-                       newManifest.size())) {
+                       const_cast<char *>(new_manifest.c_str()),
+                       new_manifest.size())) {
     fwprintf(stderr, L"Error updating resource.\n");
     return 1;
   }
-
-  if (!EndUpdateResourceW(updateHandle, false)) {
+  if (!EndUpdateResourceW(update_handle, false)) {
     fwprintf(stderr, L"Error finalizing update.\n");
     return 1;
   }