tools/gn/ninja_copy_target_writer.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "tools/gn/ninja_copy_target_writer.h"
   6
   7 #include "base/strings/string_util.h"
   8 #include "tools/gn/ninja_utils.h"
   9 #include "tools/gn/output_file.h"
  10 #include "tools/gn/scheduler.h"
  11 #include "tools/gn/string_utils.h"
  12 #include "tools/gn/substitution_list.h"
  13 #include "tools/gn/substitution_writer.h"
  14 #include "tools/gn/target.h"
  15 #include "tools/gn/toolchain.h"
  16
  17 NinjaCopyTargetWriter::NinjaCopyTargetWriter(const Target* target,
  18                                              std::ostream& out)
  19     : NinjaTargetWriter(target, out) {
  20 }
  21
  22 NinjaCopyTargetWriter::~NinjaCopyTargetWriter() {
  23 }
  24
  25 void NinjaCopyTargetWriter::Run() {
  26   const Tool* copy_tool = target_->toolchain()->GetTool(Toolchain::TYPE_COPY);
  27   if (!copy_tool) {
  28     g_scheduler->FailWithError(Err(
  29         nullptr, "Copy tool not defined",
  30         "The toolchain " +
  31             target_->toolchain()->label().GetUserVisibleName(false) +
  32             "\n used by target " + target_->label().GetUserVisibleName(false) +
  33             "\n doesn't define a \"copy\" tool."));
  34     return;
  35   }
  36
  37   const Tool* stamp_tool = target_->toolchain()->GetTool(Toolchain::TYPE_STAMP);
  38   if (!stamp_tool) {
  39     g_scheduler->FailWithError(Err(
  40         nullptr, "Copy tool not defined",
  41         "The toolchain " +
  42             target_->toolchain()->label().GetUserVisibleName(false) +
  43             "\n used by target " + target_->label().GetUserVisibleName(false) +
  44             "\n doesn't define a \"stamp\" tool."));
  45     return;
  46   }
  47
  48   // Figure out the substitutions used by the copy and stamp tools.
  49   SubstitutionBits required_bits = copy_tool->substitution_bits();
  50   required_bits.MergeFrom(stamp_tool->substitution_bits());
  51
  52   // General target-related substitutions needed by both tools.
  53   WriteSharedVars(required_bits);
  54
  55   std::vector<OutputFile> output_files;
  56   WriteCopyRules(&output_files);
  57   out_ << std::endl;
  58   WriteStampForTarget(output_files, std::vector<OutputFile>());
  59 }
  60
  61 void NinjaCopyTargetWriter::WriteCopyRules(
  62     std::vector<OutputFile>* output_files) {
  63   CHECK(target_->action_values().outputs().list().size() == 1);
  64   const SubstitutionList& output_subst_list =
  65       target_->action_values().outputs();
  66   CHECK_EQ(1u, output_subst_list.list().size())
  67       << "Should have one entry exactly.";
  68   const SubstitutionPattern& output_subst = output_subst_list.list()[0];
  69
  70   std::string tool_name =
  71       GetNinjaRulePrefixForToolchain(settings_) +
  72       Toolchain::ToolTypeToName(Toolchain::TYPE_COPY);
  73
  74   OutputFile input_dep =
  75       WriteInputDepsStampAndGetDep(std::vector<const Target*>());
  76
  77   // Note that we don't write implicit deps for copy steps. "copy" only
  78   // depends on the output files themselves, rather than having includes
  79   // (the possibility of generated #includes is the main reason for implicit
  80   // dependencies).
  81   //
  82   // It would seem that specifying implicit dependencies on the deps of the
  83   // copy command would still be harmeless. But Chrome implements copy tools
  84   // as hard links (much faster) which don't change the timestamp. If the
  85   // ninja rule looks like this:
  86   //   output: copy input | foo.stamp
  87   // The copy will not make a new timestamp on the output file, but the
  88   // foo.stamp file generated from a previous step will have a new timestamp.
  89   // The copy rule will therefore look out-of-date to Ninja and the rule will
  90   // get rebuilt.
  91   //
  92   // If this copy is copying a generated file, not listing the implicit
  93   // dependency will be fine as long as the input to the copy is properly
  94   // listed as the output from the step that generated it.
  95   //
  96   // Moreover, doing this assumes that the copy step is always a simple
  97   // locally run command, so there is no need for a toolchain dependency.
  98   //
  99   // Note that there is the need in some cases for order-only dependencies
 100   // where a command might need to make sure something else runs before it runs
 101   // to avoid conflicts. Such cases should be avoided where possible, but
 102   // sometimes that's not possible.
 103   for (const auto& input_file : target_->sources()) {
 104     OutputFile output_file =
 105         SubstitutionWriter::ApplyPatternToSourceAsOutputFile(
 106             target_->settings(), output_subst, input_file);
 107     output_files->push_back(output_file);
 108
 109     out_ << "build ";
 110     path_output_.WriteFile(out_, output_file);
 111     out_ << ": " << tool_name << " ";
 112     path_output_.WriteFile(out_, input_file);
 113     if (!input_dep.value().empty()) {
 114       out_ << " || ";
 115       path_output_.WriteFile(out_, input_dep);
 116     }
 117     out_ << std::endl;
 118   }
 119 }