Absolute path fixes for gn.

tools/gn/filesystem_utils.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/filesystem_utils.h"
 
 #include <algorithm>
 
 #include "base/files/file_util.h"
 #include "base/logging.h"
@@ skipping 502 matching lines @@
 #if defined(OS_WIN)
   for (size_t i = 0; i < path->size(); i++) {
     if ((*path)[i] == '/')
       (*path)[i] = '\\';
   }
 #endif
 }
 
 std::string MakeRelativePath(const std::string& input,
                              const std::string& dest) {
+#if defined(OS_WIN)
+  // Make sure that absolute |input| path starts with a slash if |dest| path
+  // does. Otherwise skipping common prefixes won't work properly. Ensure the
+  // same for |dest| path too.
+  if (IsPathAbsolute(input) && !IsSlash(input[0]) && IsSlash(dest[0])) {
+    std::string corrected_input(1, dest[0]);
+    corrected_input.append(input);
+    return MakeRelativePath(corrected_input, dest);
+  }
+  if (IsPathAbsolute(dest) && !IsSlash(dest[0]) && IsSlash(input[0])) {
+    std::string corrected_dest(1, input[0]);
+    corrected_dest.append(dest);
+    return MakeRelativePath(input, corrected_dest);
+  }
+#endif
+
   std::string ret;
 
   // Skip the common prefixes of the source and dest as long as they end in
   // a [back]slash.
   size_t common_prefix_len = 0;
   size_t max_common_length = std::min(input.size(), dest.size());
   for (size_t i = common_prefix_len; i < max_common_length; i++) {
     if (IsSlash(input[i]) && IsSlash(dest[i]))
       common_prefix_len = i + 1;
     else if (input[i] != dest[i])
@@ skipping 192 matching lines @@
                           source_dir.value().size() - 2);
   } else {
     // system-absolute
     const std::string& build_dir =
         settings->build_settings()->build_dir().value();
 
     if (StartsWithASCII(source_dir.value(), build_dir, true)) {
       size_t build_dir_size = build_dir.size();
       result.value().append(&source_dir.value()[build_dir_size],
                             source_dir.value().size() - build_dir_size);
+    } else {
+      result.value().append("ABS_PATH");
+#if defined(OS_WIN)
+      // Windows absolute path contains ':' after drive letter. Remove it to
+      // avoid inserting ':' in the middle of path (eg. "ABS_PATH/C:/").
+      std::string src_dir_value = source_dir.value();
+      const auto colon_pos = src_dir_value.find(':');
+      if (colon_pos != std::string::npos)
+        src_dir_value.erase(src_dir_value.begin() + colon_pos);
+#else
+      const std::string& src_dir_value = source_dir.value();
+#endif
+      result.value().append(src_dir_value);
     }
   }
   return result;
 }
 
 SourceDir GetGenDirForSourceDir(const Settings* settings,
                                 const SourceDir& source_dir) {
   return GetGenDirForSourceDirAsOutputFile(settings, source_dir).AsSourceDir(
       settings->build_settings());
 }
@@ skipping 35 matching lines @@
 
 SourceDir GetCurrentOutputDir(const Scope* scope) {
   return GetOutputDirForSourceDirAsOutputFile(
       scope->settings(), scope->GetSourceDir()).AsSourceDir(
           scope->settings()->build_settings());
 }
 
 SourceDir GetCurrentGenDir(const Scope* scope) {
   return GetGenDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }