gn: Support build directories outside the source tree.

tools/gn/substitution_writer.cc

 // Copyright 2014 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/substitution_writer.h"
 
 #include "tools/gn/build_settings.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/output_file.h"
@@ skipping 217 matching lines @@
   }
   return result_value;
 }
 
 // static
 OutputFile SubstitutionWriter::ApplyPatternToSourceAsOutputFile(
     const Settings* settings,
     const SubstitutionPattern& pattern,
     const SourceFile& source) {
   SourceFile result_as_source = ApplyPatternToSource(settings, pattern, source);
-  CHECK(result_as_source.is_source_absolute())
-      << "The result of the pattern \""
-      << pattern.AsString()
-      << "\" was not an absolute path beginning in \"//\".";
   return OutputFile(settings->build_settings(), result_as_source);
 }
 
 // static
 void SubstitutionWriter::ApplyListToSource(
     const Settings* settings,
     const SubstitutionList& list,
     const SourceFile& source,
     std::vector<SourceFile>* output) {
   for (const auto& item : list.list())
@@ skipping 99 matching lines @@
     case SUBSTITUTION_SOURCE_DIR:
       if (source.is_system_absolute())
         return DirectoryWithNoLastSlash(source.GetDir());
       to_rebase = DirectoryWithNoLastSlash(source.GetDir());
       break;
 
     case SUBSTITUTION_SOURCE_ROOT_RELATIVE_DIR:
       if (source.is_system_absolute())
         return DirectoryWithNoLastSlash(source.GetDir());
       return RebaseSourceAbsolutePath(
-          DirectoryWithNoLastSlash(source.GetDir()), SourceDir("//"));
+          DirectoryWithNoLastSlash(source.GetDir()), SourceDir("//"),
+          settings->build_settings()->root_path());
 
     case SUBSTITUTION_SOURCE_GEN_DIR:
       to_rebase = DirectoryWithNoLastSlash(
           GetGenDirForSourceDir(settings, source.GetDir()));
       break;
 
     case SUBSTITUTION_SOURCE_OUT_DIR:
       to_rebase = DirectoryWithNoLastSlash(
           GetOutputDirForSourceDir(settings, source.GetDir()));
       break;
 
     default:
       NOTREACHED()
           << "Unsupported substitution for this function: "
           << kSubstitutionNames[type];
       return std::string();
   }
 
   // If we get here, the result is a path that should be made relative or
   // absolute according to the output_style. Other cases (just file name or
   // extension extraction) will have been handled via early return above.
   if (output_style == OUTPUT_ABSOLUTE)
     return to_rebase;
-  return RebaseSourceAbsolutePath(to_rebase, relative_to);
+  return RebaseSourceAbsolutePath(to_rebase, relative_to,
+                                  settings->build_settings()->root_path());
 }
 
 // static
 OutputFile SubstitutionWriter::ApplyPatternToTargetAsOutputFile(
     const Target* target,
     const Tool* tool,
     const SubstitutionPattern& pattern) {
   std::string result_value;
   for (const auto& subrange : pattern.ranges()) {
     if (subrange.type == SUBSTITUTION_LITERAL) {
@@ skipping 153 matching lines @@
       // does not include the dot but the tool's does.
       if (target->output_extension().empty())
         return tool->default_output_extension();
       return std::string(".") + target->output_extension();
 
     default:
       NOTREACHED();
       return std::string();
   }
 }