GN: Throw an error for duplicate object files.

tools/gn/ninja_binary_target_writer.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/ninja_binary_target_writer.h"
 
 #include <cstring>
 #include <set>
 #include <sstream>
 
+#include "base/containers/hash_tables.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/config_values_extractors.h"
 #include "tools/gn/deps_iterator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/ninja_utils.h"
+#include "tools/gn/scheduler.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/source_file_type.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/substitution_writer.h"
 #include "tools/gn/target.h"
 
 // Represents a set of tool types. Must be first since it is also shared by
 // some helper functions in the anonymous namespace below.
 class NinjaBinaryTargetWriter::SourceFileTypeSet {
  public:
@@ skipping 259 matching lines @@
   //    precompiled header compile step (it outputs both the .pch file and a
   //    corresponding .obj file). So we consistently list the .obj file and the
   //    .pch file we really need comes along with it.
   std::vector<OutputFile> obj_files;
   std::vector<SourceFile> other_files;
   WriteSources(pch_obj_files, order_only_dep, &obj_files, &other_files);
 
   // Also link all pch object files.
   obj_files.insert(obj_files.end(), pch_obj_files.begin(), pch_obj_files.end());
 
+  if (!CheckForDuplicateObjectFiles(obj_files))
+    return;
+
   if (target_->output_type() == Target::SOURCE_SET) {
     WriteSourceSetStamp(obj_files);
 #ifndef NDEBUG
     // Verify that the function that separately computes a source set's object
     // files match the object files just computed.
     UniqueVector<OutputFile> computed_obj;
     AddSourceSetObjectFiles(target_, &computed_obj);
     DCHECK_EQ(obj_files.size(), computed_obj.size());
     for (const auto& obj : obj_files)
       DCHECK_NE(static_cast<size_t>(-1), computed_obj.IndexOf(obj));
@@ skipping 477 matching lines @@
   // Use "obj/{dir}/{target_name}_{lang}.pch" which ends up
   // looking like "obj/chrome/browser/browser.cc.pch"
   OutputFile ret = GetTargetOutputDirAsOutputFile(target_);
   ret.value().append(target_->label().name());
   ret.value().push_back('_');
   ret.value().append(GetPCHLangForToolType(tool_type));
   ret.value().append(".pch");
 
   return ret;
 }
+
+bool NinjaBinaryTargetWriter::CheckForDuplicateObjectFiles(
+    const std::vector<OutputFile>& files) const {
+  base::hash_set<std::string> set;
+  for (const auto& file : files) {
+    if (!set.insert(file.value()).second) {
+      Err err(
+          target_->defined_from(),
+          "Duplicate object file",
+          "The target " + target_->label().GetUserVisibleName(false) +
+          "\ngenerates two object files with the same name:\n  " +
+          file.value() + "\n"
+          "\n"
+          "It could be you accidentally have a file listed twice in the\n"
+          "sources. Or, depending on how your toolchain maps sources to\n"
+          "object files, two source files with the same name in different\n"
+          "directories could map to the same object file.\n"
+          "\n"
+          "In the latter case, either rename one of the files or move one of\n"
+          "the sources to a separate source_set to avoid them both being in\n"
+          "the same target.");
+      g_scheduler->FailWithError(err);
+      return false;
+    }
+  }
+  return true;
+}