GN: Makes GN output deterministic

tools/gn/ninja_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_writer.h"
 
 #include "tools/gn/builder.h"
 #include "tools/gn/loader.h"
 #include "tools/gn/location.h"
 #include "tools/gn/ninja_build_writer.h"
 #include "tools/gn/ninja_toolchain_writer.h"
 #include "tools/gn/settings.h"
+#include "tools/gn/target.h"
 
 NinjaWriter::NinjaWriter(const BuildSettings* build_settings,
                          Builder* builder)
     : build_settings_(build_settings),
       builder_(builder) {
 }
 
 NinjaWriter::~NinjaWriter() {
 }
 
@@ skipping 36 matching lines @@
           all_record->item()->AsTarget());
       }
   }
   if (categorized.empty()) {
     Err(Location(), "No targets.",
         "I could not find any targets to write, so I'm doing nothing.")
         .PrintToStdout();
     return false;
   }
 
+  for (auto& i : categorized) {
+    // Sort targets so that they are in a deterministic order.
+    std::sort(i.second.begin(), i.second.end(),
+              [](const Target* a, const Target* b) {
+                return a->label() < b->label();
+              });
+  }
+
   Label default_label = builder_->loader()->GetDefaultToolchain();
 
   // Write out the toolchain buildfiles, and also accumulate the set of
   // all settings and find the list of targets in the default toolchain.
-  for (CategorizedMap::const_iterator i = categorized.begin();
-       i != categorized.end(); ++i) {
+  for (const auto& i : categorized) {
     const Settings* settings =
-        builder_->loader()->GetToolchainSettings(i->first);
-    const Toolchain* toolchain = builder_->GetToolchain(i->first);
+        builder_->loader()->GetToolchainSettings(i.first);
+    const Toolchain* toolchain = builder_->GetToolchain(i.first);
 
     all_settings->push_back(settings);
-    if (!NinjaToolchainWriter::RunAndWriteFile(settings, toolchain,
-                                               i->second)) {
+
+    if (!NinjaToolchainWriter::RunAndWriteFile(settings, toolchain, i.second)) {
       Err(Location(),
           "Couldn't open toolchain buildfile(s) for writing").PrintToStdout();
       return false;
     }
   }
 
   *default_targets = categorized[default_label];
   return true;
 }
 
 bool NinjaWriter::WriteRootBuildfiles(
     const std::vector<const Settings*>& all_settings,
     const std::vector<const Target*>& default_targets,
     Err* err) {
   // All Settings objects should have the same default toolchain, and there
   // should always be at least one settings object in the build.
   CHECK(!all_settings.empty());
   const Toolchain* default_toolchain =
       builder_->GetToolchain(all_settings[0]->default_toolchain_label());
 
   // Write the root buildfile.
   return NinjaBuildWriter::RunAndWriteFile(build_settings_, all_settings,
                                            default_toolchain, default_targets,
                                            err);
 }