win: Don't show style plugin warnings for generated files.

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>
@@ skipping 112 matching lines @@
   // things through macros that were defined due to third party libraries.
   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)
-  // We need to munge the paths so that they are relative to the repository
-  // srcroot. We first resolve the symlinktastic relative path and then
-  // remove our known srcroot from it if needed.
+  // Resolve the symlinktastic relative path and make it absolute.
   char resolvedPath[MAXPATHLEN];
   if (realpath(filename.c_str(), resolvedPath)) {
     filename = resolvedPath;
   }
 #endif
 
 #if defined(LLVM_ON_WIN32)
   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(), '/');

[dcheng, 2015/04/27 22:31:21]

Would it make sense to use llvm::sys::fs::make_absolute? This seems slightly
hacky =)

[Nico, 2015/04/27 22:57:00]

That'd work too I suppose. Nothing wrong with "/c:/foo/bar" though, is there?
;-)

 #endif
 
   for (const std::string& banned_dir : banned_directories_) {
     // If any of the banned directories occur as a component in filename,
     // this file is rejected.
     assert(banned_dir.front() == '/' && "Banned dir must start with '/'");
     assert(banned_dir.back() == '/' && "Banned dir must end with '/'");
 
     if (filename.find(banned_dir) != std::string::npos)
       return true;
@@ skipping 143 matching lines @@
   PresumedLoc ploc = source_manager.getPresumedLoc(spelling_location);
   if (ploc.isInvalid()) {
     // If we're in an invalid location, we're looking at things that aren't
     // actually stated in the source.
     return false;
   }
 
   *filename = ploc.getFilename();
   return true;
 }