Absolute path fixes for gn.

tools/gn/label.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/label.h"
 
 #include "base/logging.h"
+#include "base/strings/string_util.h"
 #include "tools/gn/err.h"
+#include "tools/gn/filesystem_utils.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/value.h"
 
 namespace {
 
 // We print user visible label names with no trailing slash after the
 // directory name.
 std::string DirWithNoTrailingSlash(const SourceDir& dir) {
   // Be careful not to trim if the input is just "/" or "//".
   if (dir.value().size() > 2)
@@ skipping 67 matching lines @@
              const Label& current_toolchain,
              const Value& original_value,
              const base::StringPiece& input,
              SourceDir* out_dir,
              std::string* out_name,
              SourceDir* out_toolchain_dir,
              std::string* out_toolchain_name,
              Err* err) {
   // To workaround the problem that StringPiece operator[] doesn't return a ref.
   const char* input_str = input.data();
-
-  size_t path_separator = input.find_first_of(":(");
+  size_t offset = 0;
+#if defined(OS_WIN)
+  if (IsPathAbsolute(input)) {
+    if (input[0] != '/') {
+      *err = Err(original_value, "Bad absolute path.",
+                 "Absolute paths must be of the form /C:\\ but this is \"" +
+                     input.as_string() + "\".");
+      return false;
+    }
+    if (input.size() > 3 && input[2] == ':' && IsSlash(input[3]) &&
+        IsAsciiAlpha(input[1])) {
+      // Skip over the drive letter colon.
+      offset = 3;
+    }
+  }
+#endif
+  size_t path_separator = input.find_first_of(":(", offset);
   base::StringPiece location_piece;
   base::StringPiece name_piece;
   base::StringPiece toolchain_piece;
   if (path_separator == std::string::npos) {
     location_piece = input;
     // Leave name & toolchain piece null.
   } else {
     location_piece = base::StringPiece(&input_str[0], path_separator);
 
     size_t toolchain_separator = input.find('(', path_separator);
@@ skipping 145 matching lines @@
   }
   return ret;
 }
 
 std::string Label::GetUserVisibleName(const Label& default_toolchain) const {
   bool include_toolchain =
       default_toolchain.dir() != toolchain_dir_ ||
       default_toolchain.name() != toolchain_name_;
   return GetUserVisibleName(include_toolchain);
 }