clang plugin: Compute absolute paths on Windows as well.

tools/clang/plugins/ChromeClassTester.cpp

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A general interface for filtering and only acting on classes in Chromium C++
 // code.
 
 #include "ChromeClassTester.h"
 
 #include <algorithm>
 
 #include "clang/AST/AST.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
 
 #ifdef LLVM_ON_UNIX
 #include <sys/param.h>
 #endif
+#if defined(LLVM_ON_WIN32)
+#include <windows.h>
+#endif
 
 using namespace clang;
 using chrome_checker::Options;
 
 namespace {
 
 bool ends_with(const std::string& one, const std::string& two) {
   if (two.size() > one.size())
     return false;
 
@@ skipping 94 matching lines @@
   if (options_.no_realpath) {
     // Same reason as windows below, but we don't need to do
     // the '\\' manipulation on linux.
     filename.insert(filename.begin(), '/');
   } else if (realpath(filename.c_str(), resolvedPath)) {
     filename = resolvedPath;
   }
 #endif
 
 #if defined(LLVM_ON_WIN32)
+  // Make path absolute.
+  if (options_.no_realpath) {
+    // This turns e.g. "gen/dir/file.cc" to "/gen/dir/file.cc" which lets the
+    // "/gen/" banned_dir work.
+    filename.insert(filename.begin(), '/');
+  } else {
+    // The Windows dance: Convert to UTF-16, call GetFullPathNameW, convert back
+    DWORD size_needed =
+        MultiByteToWideChar(CP_UTF8, 0, filename.data(), -1, nullptr, 0);
+    std::wstring utf16(size_needed, L'\0');
+    MultiByteToWideChar(CP_UTF8, 0, filename.data(), -1,
+                        &utf16[0], size_needed);
+
+    size_needed = GetFullPathNameW(utf16.data(), 0, nullptr, nullptr);
+    std::wstring full_utf16(size_needed, L'\0');
+    GetFullPathNameW(utf16.data(), full_utf16.size(), &full_utf16[0], nullptr);
+
+    size_needed = WideCharToMultiByte(CP_UTF8, 0, full_utf16.data(), -1,
+                                      nullptr, 0, nullptr, nullptr);
+    filename.resize(size_needed);
+    WideCharToMultiByte(CP_UTF8, 0, full_utf16.data(), -1, &filename[0],
+                        size_needed, nullptr, nullptr);
+  }
+
   std::replace(filename.begin(), filename.end(), '\\', '/');
-
-  // On Posix, realpath() has made the path absolute.  On Windows, this isn't
-  // necessarily true, so prepend a '/' to the path to make sure the
-  // banned_directories_ loop below works correctly.
-  // This turns e.g. "gen/dir/file.cc" to "/gen/dir/file.cc" which lets the
-  // "/gen/" banned_dir work.
-  // This seems simpler than converting to utf16, calling GetFullPathNameW(),
-  // and converting back to utf8.
-  filename.insert(filename.begin(), '/');
 #endif
 
   for (const std::string& allowed_dir : allowed_directories_) {
     // If any of the allowed directories occur as a component in filename,
     // this file is allowed.
     assert(allowed_dir.front() == '/' && "Allowed dir must start with '/'");
     assert(allowed_dir.back() == '/' && "Allowed dir must end with '/'");
 
     if (filename.find(allowed_dir) != std::string::npos)
       return false;
@@ skipping 170 matching lines @@
   }
 
   *filename = ploc.getFilename();
   return true;
 }
 
 DiagnosticsEngine::Level ChromeClassTester::getErrorLevel() {
   return diagnostic().getWarningsAsErrors() ? DiagnosticsEngine::Error
                                             : DiagnosticsEngine::Warning;
 }