path: root/tools/gn/function_toolchain.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 <algorithm>
#include <limits>

#include "tools/gn/err.h"
#include "tools/gn/functions.h"
#include "tools/gn/parse_tree.h"
#include "tools/gn/scheduler.h"
#include "tools/gn/scope.h"
#include "tools/gn/settings.h"
#include "tools/gn/tool.h"
#include "tools/gn/toolchain.h"
#include "tools/gn/value_extractors.h"
#include "tools/gn/variables.h"

namespace functions {

namespace {

// This is jsut a unique value to take the address of to use as the key for
// the toolchain property on a scope.
const int kToolchainPropertyKey = 0;

bool ReadBool(Scope* scope,
              const char* var,
              Tool* tool,
              void (Tool::*set)(bool),
              Err* err) {
  const Value* v = scope->GetValue(var, true);
  if (!v)
    return true;  // Not present is fine.
  if (!v->VerifyTypeIs(Value::BOOLEAN, err))
    return false;

  (tool->*set)(v->boolean_value());
  return true;
}

// Reads the given string from the scope (if present) and puts the result into
// dest. If the value is not a string, sets the error and returns false.
bool ReadString(Scope* scope,
                const char* var,
                Tool* tool,
                void (Tool::*set)(const std::string&),
                Err* err) {
  const Value* v = scope->GetValue(var, true);
  if (!v)
    return true;  // Not present is fine.
  if (!v->VerifyTypeIs(Value::STRING, err))
    return false;

  (tool->*set)(v->string_value());
  return true;
}

// Calls the given validate function on each type in the list. On failure,
// sets the error, blame the value, and return false.
bool ValidateSubstitutionList(const std::vector<SubstitutionType>& list,
                              bool (*validate)(SubstitutionType),
                              const Value* origin,
                              Err* err) {
  for (const auto& cur_type : list) {
    if (!validate(cur_type)) {
      *err = Err(*origin, "Pattern not valid here.",
          "You used the pattern " + std::string(kSubstitutionNames[cur_type]) +
          " which is not valid\nfor this variable.");
      return false;
    }
  }
  return true;
}

bool ReadPattern(Scope* scope,
                 const char* name,
                 bool (*validate)(SubstitutionType),
                 Tool* tool,
                 void (Tool::*set)(const SubstitutionPattern&),
                 Err* err) {
  const Value* value = scope->GetValue(name, true);
  if (!value)
    return true;  // Not present is fine.
  if (!value->VerifyTypeIs(Value::STRING, err))
    return false;

  SubstitutionPattern pattern;
  if (!pattern.Parse(*value, err))
    return false;
  if (!ValidateSubstitutionList(pattern.required_types(), validate, value, err))
    return false;

  (tool->*set)(pattern);
  return true;
}

bool ReadOutputExtension(Scope* scope, Tool* tool, Err* err) {
  const Value* value = scope->GetValue("default_output_extension", true);
  if (!value)
    return true;  // Not present is fine.
  if (!value->VerifyTypeIs(Value::STRING, err))
    return false;

  if (value->string_value().empty())
    return true;  // Accept empty string.

  if (value->string_value()[0] != '.') {
    *err = Err(*value, "default_output_extension must begin with a '.'");
    return false;
  }

  tool->set_default_output_extension(value->string_value());
  return true;
}

bool ReadDepsFormat(Scope* scope, Tool* tool, Err* err) {
  const Value* value = scope->GetValue("depsformat", true);
  if (!value)
    return true;  // Not present is fine.
  if (!value->VerifyTypeIs(Value::STRING, err))
    return false;

  if (value->string_value() == "gcc") {
    tool->set_depsformat(Tool::DEPS_GCC);
  } else if (value->string_value() == "msvc") {
    tool->set_depsformat(Tool::DEPS_MSVC);
  } else {
    *err = Err(*value, "Deps format must be \"gcc\" or \"msvc\".");
    return false;
  }
  return true;
}

bool ReadOutputs(Scope* scope,
                 const FunctionCallNode* tool_function,
                 bool (*validate)(SubstitutionType),
                 Tool* tool,
                 Err* err) {
  const Value* value = scope->GetValue("outputs", true);
  if (!value) {
    *err = Err(tool_function, "\"outputs\" must be specified for this tool.");
    return false;
  }

  SubstitutionList list;
  if (!list.Parse(*value, err))
    return false;

  // Validate the right kinds of patterns are used.
  if (!ValidateSubstitutionList(list.required_types(), validate, value, err))
    return false;

  // There should always be at least one output.
  if (list.list().empty()) {
    *err = Err(*value, "Outputs list is empty.", "I need some outputs.");
    return false;
  }

  tool->set_outputs(list);
  return true;
}

bool IsCompilerTool(Toolchain::ToolType type) {
  return type == Toolchain::TYPE_CC ||
         type == Toolchain::TYPE_CXX ||
         type == Toolchain::TYPE_OBJC ||
         type == Toolchain::TYPE_OBJCXX ||
         type == Toolchain::TYPE_RC ||
         type == Toolchain::TYPE_ASM;
}

bool IsLinkerTool(Toolchain::ToolType type) {
  return type == Toolchain::TYPE_ALINK ||
         type == Toolchain::TYPE_SOLINK ||
         type == Toolchain::TYPE_LINK;
}

bool IsPatternInOutputList(const SubstitutionList& output_list,
                           const SubstitutionPattern& pattern) {
  for (const auto& cur : output_list.list()) {
    if (pattern.ranges().size() == cur.ranges().size() &&
        std::equal(pattern.ranges().begin(), pattern.ranges().end(),
                   cur.ranges().begin()))
      return true;
  }
  return false;
}

}  // namespace

// toolchain -------------------------------------------------------------------

const char kToolchain[] = "toolchain";
const char kToolchain_HelpShort[] =
    "toolchain: Defines a toolchain.";
const char kToolchain_Help[] =
    "toolchain: Defines a toolchain.\n"
    "\n"
    "  A toolchain is a set of commands and build flags used to compile the\n"
    "  source code. You can have more than one toolchain in use at once in\n"
    "  a build.\n"
    "\n"
    "Functions and variables\n"
    "\n"
    "  tool()\n"
    "    The tool() function call specifies the commands commands to run for\n"
    "    a given step. See \"gn help tool\".\n"
    "\n"
    "  toolchain_args()\n"
    "    List of arguments to pass to the toolchain when invoking this\n"
    "    toolchain. This applies only to non-default toolchains. See\n"
    "    \"gn help toolchain_args\" for more.\n"
    "\n"
    "  deps\n"
    "    Dependencies of this toolchain. These dependencies will be resolved\n"
    "    before any target in the toolchain is compiled. To avoid circular\n"
    "    dependencies these must be targets defined in another toolchain.\n"
    "\n"
    "    This is expressed as a list of targets, and generally these targets\n"
    "    will always specify a toolchain:\n"
    "      deps = [ \"//foo/bar:baz(//build/toolchain:bootstrap)\" ]\n"
    "\n"
    "    This concept is somewhat inefficient to express in Ninja (it\n"
    "    requires a lot of duplicate of rules) so should only be used when\n"
    "    absolutely necessary.\n"
    "\n"
    "  concurrent_links\n"
    "    In integer expressing the number of links that Ninja will perform in\n"
    "    parallel. GN will create a pool for shared library and executable\n"
    "    link steps with this many processes. Since linking is memory- and\n"
    "    I/O-intensive, projects with many large targets may want to limit\n"
    "    the number of parallel steps to avoid overloading the computer.\n"
    "    Since creating static libraries is generally not as intensive\n"
    "    there is no limit to \"alink\" steps.\n"
    "\n"
    "    Defaults to 0 which Ninja interprets as \"no limit\".\n"
    "\n"
    "    The value used will be the one from the default toolchain of the\n"
    "    current build.\n"
    "\n"
    "Invoking targets in toolchains:\n"
    "\n"
    "  By default, when a target depends on another, there is an implicit\n"
    "  toolchain label that is inherited, so the dependee has the same one\n"
    "  as the dependent.\n"
    "\n"
    "  You can override this and refer to any other toolchain by explicitly\n"
    "  labeling the toolchain to use. For example:\n"
    "    data_deps = [ \"//plugins:mine(//toolchains:plugin_toolchain)\" ]\n"
    "  The string \"//build/toolchains:plugin_toolchain\" is a label that\n"
    "  identifies the toolchain declaration for compiling the sources.\n"
    "\n"
    "  To load a file in an alternate toolchain, GN does the following:\n"
    "\n"
    "   1. Loads the file with the toolchain definition in it (as determined\n"
    "      by the toolchain label).\n"
    "   2. Re-runs the master build configuration file, applying the\n"
    "      arguments specified by the toolchain_args section of the toolchain\n"
    "      definition (see \"gn help toolchain_args\").\n"
    "   3. Loads the destination build file in the context of the\n"
    "      configuration file in the previous step.\n"
    "\n"
    "Example:\n"
    "  toolchain(\"plugin_toolchain\") {\n"
    "    concurrent_links = 8\n"
    "\n"
    "    tool(\"cc\") {\n"
    "      command = \"gcc $in\"\n"
    "      ...\n"
    "    }\n"
    "\n"
    "    toolchain_args() {\n"
    "      is_plugin = true\n"
    "      is_32bit = true\n"
    "      is_64bit = false\n"
    "    }\n"
    "  }\n";

Value RunToolchain(Scope* scope,
                   const FunctionCallNode* function,
                   const std::vector<Value>& args,
                   BlockNode* block,
                   Err* err) {
  if (!EnsureNotProcessingImport(function, scope, err) ||
      !EnsureNotProcessingBuildConfig(function, scope, err))
    return Value();

  // Note that we don't want to use MakeLabelForScope since that will include
  // the toolchain name in the label, and toolchain labels don't themselves
  // have toolchain names.
  const SourceDir& input_dir = scope->GetSourceDir();
  Label label(input_dir, args[0].string_value());
  if (g_scheduler->verbose_logging())
    g_scheduler->Log("Definining toolchain", label.GetUserVisibleName(false));

  // This object will actually be copied into the one owned by the toolchain
  // manager, but that has to be done in the lock.
  scoped_ptr<Toolchain> toolchain(new Toolchain(scope->settings(), label));
  toolchain->set_defined_from(function);
  toolchain->visibility().SetPublic();

  Scope block_scope(scope);
  block_scope.SetProperty(&kToolchainPropertyKey, toolchain.get());
  block->ExecuteBlockInScope(&block_scope, err);
  block_scope.SetProperty(&kToolchainPropertyKey, NULL);
  if (err->has_error())
    return Value();

  // Read deps (if any).
  const Value* deps_value = block_scope.GetValue(variables::kDeps, true);
  if (deps_value) {
    ExtractListOfLabels(
        *deps_value, block_scope.GetSourceDir(),
        ToolchainLabelForScope(&block_scope), &toolchain->deps(), err);
    if (err->has_error())
      return Value();
  }

  // Read concurrent_links (if any).
  const Value* concurrent_links_value =
      block_scope.GetValue("concurrent_links", true);
  if (concurrent_links_value) {
    if (!concurrent_links_value->VerifyTypeIs(Value::INTEGER, err))
      return Value();
    if (concurrent_links_value->int_value() < 0 ||
        concurrent_links_value->int_value() > std::numeric_limits<int>::max()) {
      *err = Err(*concurrent_links_value, "Value out of range.");
      return Value();
    }
    toolchain->set_concurrent_links(
        static_cast<int>(concurrent_links_value->int_value()));
  }

  if (!block_scope.CheckForUnusedVars(err))
    return Value();

  // Save this toolchain.
  toolchain->ToolchainSetupComplete();
  Scope::ItemVector* collector = scope->GetItemCollector();
  if (!collector) {
    *err = Err(function, "Can't define a toolchain in this context.");
    return Value();
  }
  collector->push_back(new scoped_ptr<Item>(toolchain.PassAs<Item>()));
  return Value();
}

// tool ------------------------------------------------------------------------

const char kTool[] = "tool";
const char kTool_HelpShort[] =
    "tool: Specify arguments to a toolchain tool.";
const char kTool_Help[] =
    "tool: Specify arguments to a toolchain tool.\n"
    "\n"
    "Usage:\n"
    "\n"
    "  tool(<tool type>) {\n"
    "    <tool variables...>\n"
    "  }\n"
    "\n"
    "Tool types\n"
    "\n"
    "    Compiler tools:\n"
    "      \"cc\": C compiler\n"
    "      \"cxx\": C++ compiler\n"
    "      \"objc\": Objective C compiler\n"
    "      \"objcxx\": Objective C++ compiler\n"
    "      \"rc\": Resource compiler (Windows .rc files)\n"
    "      \"asm\": Assembler\n"
    "\n"
    "    Linker tools:\n"
    "      \"alink\": Linker for static libraries (archives)\n"
    "      \"solink\": Linker for shared libraries\n"
    "      \"link\": Linker for executables\n"
    "\n"
    "    Other tools:\n"
    "      \"stamp\": Tool for creating stamp files\n"
    "      \"copy\": Tool to copy files.\n"
    "\n"
    "Tool variables\n"
    "\n"
    "    command  [string with substitutions]\n"
    "        Valid for: all tools (required)\n"
    "\n"
    "        The command to run.\n"
    "\n"
    "    default_output_extension  [string]\n"
    "        Valid for: linker tools\n"
    "\n"
    "        Extension for the main output of a linkable tool. It includes\n"
    "        the leading dot. This will be the default value for the\n"
    "        {{output_extension}} expansion (discussed below) but will be\n"
    "        overridden by by the \"output extension\" variable in a target,\n"
    "        if one is specified. Empty string means no extension.\n"
    "\n"
    "        GN doesn't actually do anything with this extension other than\n"
    "        pass it along, potentially with target-specific overrides. One\n"
    "        would typically use the {{output_extension}} value in the\n"
    "        \"outputs\" to read this value.\n"
    "\n"
    "        Example: default_output_extension = \".exe\"\n"
    "\n"
    "    depfile  [string]\n"
    "        Valid for: compiler tools (optional)\n"
    "\n"
    "        If the tool can write \".d\" files, this specifies the name of\n"
    "        the resulting file. These files are used to list header file\n"
    "        dependencies (or other implicit input dependencies) that are\n"
    "        discovered at build time. See also \"depsformat\".\n"
    "\n"
    "        Example: depfile = \"{{output}}.d\"\n"
    "\n"
    "    depsformat  [string]\n"
    "        Valid for: compiler tools (when depfile is specified)\n"
    "\n"
    "        Format for the deps outputs. This is either \"gcc\" or \"msvc\".\n"
    "        See the ninja documentation for \"deps\" for more information.\n"
    "\n"
    "        Example: depsformat = \"gcc\"\n"
    "\n"
    "    description  [string with substitutions, optional]\n"
    "        Valid for: all tools\n"
    "\n"
    "        What to print when the command is run.\n"
    "\n"
    "        Example: description = \"Compiling {{source}}\"\n"
    "\n"
    "    lib_switch  [string, optional, link tools only]\n"
    "    lib_dir_switch  [string, optional, link tools only]\n"
    "        Valid for: Linker tools except \"alink\"\n"
    "\n"
    "        These strings will be prepended to the libraries and library\n"
    "        search directories, respectively, because linkers differ on how\n"
    "        specify them. If you specified:\n"
    "          lib_switch = \"-l\"\n"
    "          lib_dir_switch = \"-L\"\n"
    "        then the \"{{libs}}\" expansion for [ \"freetype\", \"expat\"]\n"
    "        would be \"-lfreetype -lexpat\".\n"
    "\n"
    "    outputs  [list of strings with substitutions]\n"
    "        Valid for: Linker and compiler tools (required)\n"
    "\n"
    "        An array of names for the output files the tool produces. These\n"
    "        are relative to the build output directory. There must always be\n"
    "        at least one output file. There can be more than one output (a\n"
    "        linker might produce a library and an import library, for\n"
    "        example).\n"
    "\n"
    "        This array just declares to GN what files the tool will\n"
    "        produce. It is your responsibility to specify the tool command\n"
    "        that actually produces these files.\n"
    "\n"
    "        If you specify more than one output for shared library links,\n"
    "        you should consider setting link_output and depend_output.\n"
    "        Otherwise, the first entry in the outputs list should always be\n"
    "        the main output which will be linked to.\n"
    "\n"
    "        Example for a compiler tool that produces .obj files:\n"
    "          outputs = [\n"
    "            \"{{source_out_dir}}/{{source_name_part}}.obj\"\n"
    "          ]\n"
    "\n"
    "        Example for a linker tool that produces a .dll and a .lib. The\n"
    "        use of {{output_extension}} rather than hardcoding \".dll\"\n"
    "        allows the extension of the library to be overridden on a\n"
    "        target-by-target basis, but in this example, it always\n"
    "        produces a \".lib\" import library:\n"
    "          outputs = [\n"
    "            \"{{root_out_dir}}/{{target_output_name}}"
                     "{{output_extension}}\",\n"
    "            \"{{root_out_dir}}/{{target_output_name}}.lib\",\n"
    "          ]\n"
    "\n"
    "    link_output  [string with substitutions]\n"
    "    depend_output  [string with substitutions]\n"
    "        Valid for: \"solink\" only (optional)\n"
    "\n"
    "        These two files specify whch of the outputs from the solink\n"
    "        tool should be used for linking and dependency tracking. These\n"
    "        should match entries in the \"outputs\". If unspecified, the\n"
    "        first item in the \"outputs\" array will be used for both. See\n"
    "        \"Separate linking and dependencies for shared libraries\"\n"
    "        below for more.\n"
    "\n"
    "        On Windows, where the tools produce a .dll shared library and\n"
    "        a .lib import library, you will want both of these to be the\n"
    "        import library. On Linux, if you're not doing the separate\n"
    "        linking/dependency optimization, both of these should be the\n"
    "        .so output.\n"
    "\n"
    "    output_prefix  [string]\n"
    "        Valid for: Linker tools (optional)\n"
    "\n"
    "        Prefix to use for the output name. Defaults to empty. This\n"
    "        prefix will be prepended to the name of the target (or the\n"
    "        output_name if one is manually specified for it) if the prefix\n"
    "        is not already there. The result will show up in the\n"
    "        {{output_name}} substitution pattern.\n"
    "\n"
    "        This is typically used to prepend \"lib\" to libraries on\n"
    "        Posix systems:\n"
    "          output_prefix = \"lib\"\n"
    "\n"
    "    restat  [boolean]\n"
    "        Valid for: all tools (optional, defaults to false)\n"
    "\n"
    "        Requests that Ninja check the file timestamp after this tool has\n"
    "        run to determine if anything changed. Set this if your tool has\n"
    "        the ability to skip writing output if the output file has not\n"
    "        changed.\n"
    "\n"
    "        Normally, Ninja will assume that when a tool runs the output\n"
    "        be new and downstream dependents must be rebuild. When this is\n"
    "        set to trye, Ninja can skip rebuilding downstream dependents for\n"
    "        input changes that don't actually affect the output.\n"
    "\n"
    "        Example:\n"
    "          restat = true\n"
    "\n"
    "    rspfile  [string with substitutions]\n"
    "        Valid for: all tools (optional)\n"
    "\n"
    "        Name of the response file. If empty, no response file will be\n"
    "        used. See \"rspfile_content\".\n"
    "\n"
    "    rspfile_content  [string with substitutions]\n"
    "        Valid for: all tools (required when \"rspfile\" is specified)\n"
    "\n"
    "        The contents to be written to the response file. This may\n"
    "        include all or part of the command to send to the tool which\n"
    "        allows you to get around OS command-line length limits.\n"
    "\n"
    "        This example adds the inputs and libraries to a response file,\n"
    "        but passes the linker flags directly on the command line:\n"
    "          tool(\"link\") {\n"
    "            command = \"link -o {{output}} {{ldflags}} @{{output}}.rsp\"\n"
    "            rspfile = \"{{output}}.rsp\"\n"
    "            rspfile_content = \"{{inputs}} {{solibs}} {{libs}}\"\n"
    "          }\n"
    "\n"
    "Expansions for tool variables"
    "\n"
    "  All paths are relative to the root build directory, which is the\n"
    "  current directory for running all tools. These expansions are\n"
    "  available to all tools:\n"
    "\n"
    "    {{label}}\n"
    "        The label of the current target. This is typically used in the\n"
    "        \"description\" field for link tools. The toolchain will be\n"
    "        omitted from the label for targets in the default toolchain, and\n"
    "        will be included for targets in other toolchains.\n"
    "\n"
    "    {{output}}\n"
    "        The relative path and name of the output)((s) of the current\n"
    "        build step. If there is more than one output, this will expand\n"
    "        to a list of all of them.\n"
    "        Example: \"out/base/my_file.o\"\n"
    "\n"
    "    {{target_gen_dir}}\n"
    "    {{target_out_dir}}\n"
    "        The directory of the generated file and output directories,\n"
    "        respectively, for the current target. There is no trailing\n"
    "        slash.\n"
    "        Example: \"out/base/test\"\n"
    "\n"
    "    {{target_output_name}}\n"
    "        The short name of the current target with no path information,\n"
    "        or the value of the \"output_name\" variable if one is specified\n"
    "        in the target. This will include the \"output_prefix\" if any.\n"
    "        Example: \"libfoo\" for the target named \"foo\" and an\n"
    "        output prefix for the linker tool of \"lib\".\n"
    "\n"
    "  Compiler tools have the notion of a single input and a single output,\n"
    "  along with a set of compiler-specific flags. The following expansions\n"
    "  are available:\n"
    "\n"
    "    {{cflags}}\n"
    "    {{cflags_c}}\n"
    "    {{cflags_cc}}\n"
    "    {{cflags_objc}}\n"
    "    {{cflags_objcc}}\n"
    "    {{defines}}\n"
    "    {{include_dirs}}\n"
    "        Strings correspond that to the processed flags/defines/include\n"
    "        directories specified for the target.\n"
    "        Example: \"--enable-foo --enable-bar\"\n"
    "\n"
    "        Defines will be prefixed by \"-D\" and include directories will\n"
    "        be prefixed by \"-I\" (these work with Posix tools as well as\n"
    "        Microsoft ones).\n"
    "\n"
    "    {{source}}\n"
    "        The relative path and name of the current input file.\n"
    "        Example: \"../../base/my_file.cc\"\n"
    "\n"
    "    {{source_file_part}}\n"
    "        The file part of the source including the extension (with no\n"
    "        directory information).\n"
    "        Example: \"foo.cc\"\n"
    "\n"
    "    {{source_name_part}}\n"
    "        The filename part of the source file with no directory or\n"
    "        extension.\n"
    "        Example: \"foo\"\n"
    "\n"
    "    {{source_gen_dir}}\n"
    "    {{source_out_dir}}\n"
    "        The directory in the generated file and output directories,\n"
    "        respectively, for the current input file. If the source file\n"
    "        is in the same directory as the target is declared in, they will\n"
    "        will be the same as the \"target\" versions above.\n"
    "        Example: \"gen/base/test\"\n"
    "\n"
    "  Linker tools have multiple inputs and (potentially) multiple outputs\n"
    "  The following expansions are available:\n"
    "\n"
    "    {{inputs}}\n"
    "    {{inputs_newline}}\n"
    "        Expands to the inputs to the link step. This will be a list of\n"
    "        object files and static libraries.\n"
    "        Example: \"obj/foo.o obj/bar.o obj/somelibrary.a\"\n"
    "\n"
    "        The \"_newline\" version will separate the input files with\n"
    "        newlines instead of spaces. This is useful in response files:\n"
    "        some linkers can take a \"-filelist\" flag which expects newline\n"
    "        separated files, and some Microsoft tools have a fixed-sized\n"
    "        buffer for parsing each line of a response file.\n"
    "\n"
    "    {{ldflags}}\n"
    "        Expands to the processed set of ldflags and library search paths\n"
    "        specified for the target.\n"
    "        Example: \"-m64, -fPIC -pthread -L/usr/local/mylib\"\n"
    "\n"
    "    {{libs}}\n"
    "        Expands to the list of system libraries to link to. Each will\n"
    "        be prefixed by the \"lib_prefix\".\n"
    "\n"
    "        As a special case to support Mac, libraries with names ending in\n"
    "        \".framework\" will be added to the {{libs}} with \"-framework\"\n"
    "        preceeding it, and the lib prefix will be ignored.\n"
    "\n"
    "        Example: \"-lfoo -lbar\"\n"
    "\n"
    "    {{output_extension}}\n"
    "        The value of the \"output_extension\" variable in the target,\n"
    "        or the value of the \"default_output_extension\" value in the\n"
    "        tool if the target does not specify an output extension.\n"
    "        Example: \".so\"\n"
    "\n"
    "    {{solibs}}\n"
    "        Extra libraries from shared library dependencide not specified\n"
    "        in the {{inputs}}. This is the list of link_output files from\n"
    "        shared libraries (if the solink tool specifies a \"link_output\"\n"
    "        variable separate from the \"depend_output\").\n"
    "\n"
    "        These should generally be treated the same as libs by your tool.\n"
    "        Example: \"libfoo.so libbar.so\"\n"
    "\n"
    "  The copy tool allows the common compiler/linker substitutions, plus\n"
    "  {{source}} which is the source of the copy. The stamp tool allows\n"
    "  only the common tool substitutions.\n"
    "\n"
    "Separate linking and dependencies for shared libraries\n"
    "\n"
    "  Shared libraries are special in that not all changes to them require\n"
    "  that dependent targets be re-linked. If the shared library is changed\n"
    "  but no imports or exports are different, dependent code needn't be\n"
    "  relinked, which can speed up the build.\n"
    "\n"
    "  If your link step can output a list of exports from a shared library\n"
    "  and writes the file only if the new one is different, the timestamp of\n"
    "  this file can be used for triggering re-links, while the actual shared\n"
    "  library would be used for linking.\n"
    "\n"
    "  You will need to specify\n"
    "    restat = true\n"
    "  in the linker tool to make this work, so Ninja will detect if the\n"
    "  timestamp of the dependency file has changed after linking (otherwise\n"
    "  it will always assume that running a command updates the output):\n"
    "\n"
    "    tool(\"solink\") {\n"
    "      command = \"...\"\n"
    "      outputs = [\n"
    "        \"{{root_out_dir}}/{{target_output_name}}{{output_extension}}\",\n"
    "        \"{{root_out_dir}}/{{target_output_name}}"
                 "{{output_extension}}.TOC\",\n"
    "      ]\n"
    "      link_output =\n"
    "        \"{{root_out_dir}}/{{target_output_name}}{{output_extension}}\",\n"
    "      depend_output =\n"
    "        \"{{root_out_dir}}/{{target_output_name}}"
                 "{{output_extension}}.TOC\",\n"
    "      restat = true\n"
    "    }\n"
    "\n"
    "Example\n"
    "\n"
    "  toolchain(\"my_toolchain\") {\n"
    "    # Put these at the top to apply to all tools below.\n"
    "    lib_prefix = \"-l\"\n"
    "    lib_dir_prefix = \"-L\"\n"
    "\n"
    "    tool(\"cc\") {\n"
    "      command = \"gcc \\$in -o \\$out\"\n"
    "      outputs = [ \"{{source_out_dir}}/{{source_name_part}}.o\"\n"
    "      description = \"GCC \\$in\"\n"
    "    }\n"
    "    tool(\"cxx\") {\n"
    "      command = \"g++ \\$in -o \\$out\"\n"
    "      outputs = [ \"{{source_out_dir}}/{{source_name_part}}.o\"\n"
    "      description = \"G++ \\$in\"\n"
    "    }\n"
    "  }\n";

Value RunTool(Scope* scope,
              const FunctionCallNode* function,
              const std::vector<Value>& args,
              BlockNode* block,
              Err* err) {
  // Find the toolchain definition we're executing inside of. The toolchain
  // function will set a property pointing to it that we'll pick up.
  Toolchain* toolchain = reinterpret_cast<Toolchain*>(
      scope->GetProperty(&kToolchainPropertyKey, NULL));
  if (!toolchain) {
    *err = Err(function->function(), "tool() called outside of toolchain().",
        "The tool() function can only be used inside a toolchain() "
        "definition.");
    return Value();
  }

  if (!EnsureSingleStringArg(function, args, err))
    return Value();
  const std::string& tool_name = args[0].string_value();
  Toolchain::ToolType tool_type = Toolchain::ToolNameToType(tool_name);
  if (tool_type == Toolchain::TYPE_NONE) {
    *err = Err(args[0], "Unknown tool type");
    return Value();
  }

  // Run the tool block.
  Scope block_scope(scope);
  block->ExecuteBlockInScope(&block_scope, err);
  if (err->has_error())
    return Value();

  // Figure out which validator to use for the substitution pattern for this
  // tool type. There are different validators for the "outputs" than for the
  // rest of the strings.
  bool (*subst_validator)(SubstitutionType) = NULL;
  bool (*subst_output_validator)(SubstitutionType) = NULL;
  if (IsCompilerTool(tool_type)) {
    subst_validator = &IsValidCompilerSubstitution;
    subst_output_validator = &IsValidCompilerOutputsSubstitution;
  } else if (IsLinkerTool(tool_type)) {
    subst_validator = &IsValidLinkerSubstitution;
    subst_output_validator = &IsValidLinkerOutputsSubstitution;
  } else if (tool_type == Toolchain::TYPE_COPY) {
    subst_validator = &IsValidCopySubstitution;
    subst_output_validator = &IsValidCopySubstitution;
  } else {
    subst_validator = &IsValidToolSubstutition;
    subst_output_validator = &IsValidToolSubstutition;
  }

  scoped_ptr<Tool> tool(new Tool);

  if (!ReadPattern(&block_scope, "command", subst_validator, tool.get(),
                   &Tool::set_command, err) ||
      !ReadOutputExtension(&block_scope, tool.get(), err) ||
      !ReadPattern(&block_scope, "depfile", subst_validator, tool.get(),
                   &Tool::set_depfile, err) ||
      !ReadDepsFormat(&block_scope, tool.get(), err) ||
      !ReadPattern(&block_scope, "description", subst_validator, tool.get(),
                   &Tool::set_description, err) ||
      !ReadString(&block_scope, "lib_switch", tool.get(),
                  &Tool::set_lib_switch, err) ||
      !ReadString(&block_scope, "lib_dir_switch", tool.get(),
                  &Tool::set_lib_dir_switch, err) ||
      !ReadPattern(&block_scope, "link_output", subst_validator, tool.get(),
                   &Tool::set_link_output, err) ||
      !ReadPattern(&block_scope, "depend_output", subst_validator, tool.get(),
                   &Tool::set_depend_output, err) ||
      !ReadString(&block_scope, "output_prefix", tool.get(),
                  &Tool::set_output_prefix, err) ||
      !ReadBool(&block_scope, "restat", tool.get(), &Tool::set_restat, err) ||
      !ReadPattern(&block_scope, "rspfile", subst_validator, tool.get(),
                   &Tool::set_rspfile, err) ||
      !ReadPattern(&block_scope, "rspfile_content", subst_validator, tool.get(),
                   &Tool::set_rspfile_content, err)) {
    return Value();
  }

  if (tool_type != Toolchain::TYPE_COPY && tool_type != Toolchain::TYPE_STAMP) {
    // All tools except the copy and stamp tools should have outputs. The copy
    // and stamp tool's outputs are generated internally.
    if (!ReadOutputs(&block_scope, function, subst_output_validator,
                     tool.get(), err))
      return Value();
  }

  // Validate that the link_output and depend_output refer to items in the
  // outputs and aren't defined for irrelevant tool types.
  if (!tool->link_output().empty()) {
    if (tool_type != Toolchain::TYPE_SOLINK) {
      *err = Err(function, "This tool specifies a link_output.",
          "This is only valid for solink tools.");
      return Value();
    }
    if (!IsPatternInOutputList(tool->outputs(), tool->link_output())) {
      *err = Err(function, "This tool's link_output is bad.",
                 "It must match one of the outputs.");
      return Value();
    }
  }
  if (!tool->depend_output().empty()) {
    if (tool_type != Toolchain::TYPE_SOLINK) {
      *err = Err(function, "This tool specifies a depend_output.",
          "This is only valid for solink tools.");
      return Value();
    }
    if (!IsPatternInOutputList(tool->outputs(), tool->depend_output())) {
      *err = Err(function, "This tool's depend_output is bad.",
                 "It must match one of the outputs.");
      return Value();
    }
  }
  if ((!tool->link_output().empty() && tool->depend_output().empty()) ||
      (tool->link_output().empty() && !tool->depend_output().empty())) {
    *err = Err(function, "Both link_output and depend_output should either "
        "be specified or they should both be empty.");
    return Value();
  }

  // Make sure there weren't any vars set in this tool that were unused.
  if (!block_scope.CheckForUnusedVars(err))
    return Value();

  toolchain->SetTool(tool_type, tool.Pass());
  return Value();
}

// toolchain_args --------------------------------------------------------------

extern const char kToolchainArgs[] = "toolchain_args";
extern const char kToolchainArgs_HelpShort[] =
    "toolchain_args: Set build arguments for toolchain build setup.";
extern const char kToolchainArgs_Help[] =
    "toolchain_args: Set build arguments for toolchain build setup.\n"
    "\n"
    "  Used inside a toolchain definition to pass arguments to an alternate\n"
    "  toolchain's invocation of the build.\n"
    "\n"
    "  When you specify a target using an alternate toolchain, the master\n"
    "  build configuration file is re-interpreted in the context of that\n"
    "  toolchain (see \"gn help toolchain\"). The toolchain_args function\n"
    "  allows you to control the arguments passed into this alternate\n"
    "  invocation of the build.\n"
    "\n"
    "  Any default system arguments or arguments passed in on the command-\n"
    "  line will also be passed to the alternate invocation unless explicitly\n"
    "  overridden by toolchain_args.\n"
    "\n"
    "  The toolchain_args will be ignored when the toolchain being defined\n"
    "  is the default. In this case, it's expected you want the default\n"
    "  argument values.\n"
    "\n"
    "  See also \"gn help buildargs\" for an overview of these arguments.\n"
    "\n"
    "Example:\n"
    "  toolchain(\"my_weird_toolchain\") {\n"
    "    ...\n"
    "    toolchain_args() {\n"
    "      # Override the system values for a generic Posix system.\n"
    "      is_win = false\n"
    "      is_posix = true\n"
    "\n"
    "      # Pass this new value for specific setup for my toolchain.\n"
    "      is_my_weird_system = true\n"
    "    }\n"
    "  }\n";

Value RunToolchainArgs(Scope* scope,
                       const FunctionCallNode* function,
                       const std::vector<Value>& args,
                       BlockNode* block,
                       Err* err) {
  // Find the toolchain definition we're executing inside of. The toolchain
  // function will set a property pointing to it that we'll pick up.
  Toolchain* toolchain = reinterpret_cast<Toolchain*>(
      scope->GetProperty(&kToolchainPropertyKey, NULL));
  if (!toolchain) {
    *err = Err(function->function(),
               "toolchain_args() called outside of toolchain().",
               "The toolchain_args() function can only be used inside a "
               "toolchain() definition.");
    return Value();
  }

  if (!args.empty()) {
    *err = Err(function->function(), "This function takes no arguments.");
    return Value();
  }

  // This function makes a new scope with various variable sets on it, which
  // we then save on the toolchain to use when re-invoking the build.
  Scope block_scope(scope);
  block->ExecuteBlockInScope(&block_scope, err);
  if (err->has_error())
    return Value();

  Scope::KeyValueMap values;
  block_scope.GetCurrentScopeValues(&values);
  toolchain->args() = values;

  return Value();
}

}  // namespace functions