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 83 matching lines @@
   if (filename == "<scratch space>")
     return true;
 
   // Don't complain about autogenerated protobuf files.
   if (ends_with(filename, ".pb.h")) {
     return true;
   }
 
 #if defined(LLVM_ON_UNIX)
   // Resolve the symlinktastic relative path and make it absolute.
-  char resolvedPath[MAXPATHLEN];
   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)) {
+    char resolvedPath[MAXPATHLEN];
     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, 0);

[dcheng, 2016/09/09 18:57:29]

Nit: '\0' maybe, for slightly better clarity?

[Nico, 2016/09/09 19:06:33]

meh, it's overwritten below anyways. And wouldn't it have to be L'\0'?

[dcheng, 2016/09/09 19:09:48]

I think '\0' should work fine here: the L prefix is only a problem for string
literals since the pointer types aren't convertible.

(It's just a visual hint to the reader that the first parameter is the count:
even though we're passing a named variable as the count, there's still a bare 0
integer literal right next to it, so it takes me a little extra mental energy to
remember that this is a character, not NULL or a count of some other sort)

+    MultiByteToWideChar(CP_UTF8, 0, filename.data(), -1,
+                        &utf16[0], size_needed);
+
+    size_needed = GetFullPathName(utf16.data(), 0, nullptr, nullptr) + 1; // nul

[dcheng, 2016/09/09 18:57:29]

Nit: let's be consistent about calling the W versions.

[dcheng, 2016/09/09 18:57:29]

Also:

If the lpBuffer buffer is too small to contain the path, the return value is the
size, in TCHARs, of the buffer that is required to hold the path and the
terminating null character.

So I think this already includes the terminating null.

[Nico, 2016/09/09 19:06:33]

Oh oops, done, thanks!

[Nico, 2016/09/09 19:06:33]

You're right, I misread the docs. Done.

+    std::wstring full_utf16(size_needed, 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;
 }