Add initial prototype for the GN meta-buildsystem.

tools/gn/toolchain_manager.cc

Index: tools/gn/toolchain_manager.cc
diff --git a/tools/gn/toolchain_manager.cc b/tools/gn/toolchain_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8a54163c705997ccdb2b8ee3936502bcbbdc1515
--- /dev/null
+++ b/tools/gn/toolchain_manager.cc
@@ -0,0 +1,480 @@
+// 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/toolchain_manager.h"
+
+#include <set>
+
+#include "base/bind.h"
+#include "tools/gn/err.h"
+#include "tools/gn/item.h"
+#include "tools/gn/item_node.h"
+#include "tools/gn/item_tree.h"
+#include "tools/gn/parse_tree.h"
+#include "tools/gn/scheduler.h"
+#include "tools/gn/scope.h"
+#include "tools/gn/scope_per_file_provider.h"
+
+namespace {
+
+SourceFile DirToBuildFile(const SourceDir& dir) {
+  return SourceFile(dir.value() + "BUILD.gn");
+}
+
+void SetSystemVars(const Settings& settings, Scope* scope) {
+  // FIXME(brettw) port.
+  scope->SetValue("is_win", Value(NULL, 1), NULL);
+  scope->SetValue("is_linux", Value(NULL, 0), NULL);
+  scope->SetValue("is_posix", Value(NULL, 0), NULL);
+  scope->SetValue("is_mac", Value(NULL, 0), NULL);
+  scope->SetValue("is_android", Value(NULL, 0), NULL);
+  scope->SetValue("is_ios", Value(NULL, 0), NULL);
+
+  // Set this value without the terminating slash because the code expects
+  // $root_output_dir/foo to work.
+  scope->SetValue(ScopePerFileProvider::kRootOutputDirName,
+                  ScopePerFileProvider::GetRootOutputDir(&settings),
+                  NULL);
+  scope->SetValue(ScopePerFileProvider::kRootGenDirName,
+                  ScopePerFileProvider::GetRootGenDir(&settings),
+                  NULL);
+}
+
+}  // namespace
+
+struct ToolchainManager::Info {
+  Info(const BuildSettings* build_settings,
+       const Label& toolchain_name,
+       const std::string& output_subdir_name)
+      : state(TOOLCHAIN_SETTINGS_NOT_LOADED),
+        toolchain(toolchain_name),
+        toolchain_set(false),
+        settings(build_settings, &toolchain, output_subdir_name),
+        item_node(NULL) {
+  }
+
+  // MAkes sure that an ItemNode is created for the toolchain, which lets
+  // targets depend on the (potentially future) loading of the toolchain.
+  //
+  // We can't always do this at the beginning since when doing the default
+  // build config, we don't know the toolchain name yet. We also need to go
+  // through some effort to avoid doing this inside the toolchain manager's
+  // lock (to avoid holding two locks at once).
+  void EnsureItemNode() {
+    if (!item_node) {
+      ItemTree& tree = settings.build_settings()->item_tree();
+      item_node = new ItemNode(&toolchain);
+      tree.AddNodeLocked(item_node);
+    }
+  }
+
+  SettingsState state;
+
+  Toolchain toolchain;
+  bool toolchain_set;
+  LocationRange toolchain_definition_location;
+
+  // When the state is TOOLCHAIN_SETTINGS_LOADED, the settings should be
+  // considered read-only and can be read without locking. Otherwise, they
+  // should not be accessed at all except to load them (which can therefore
+  // also be done outside of the lock). This works as long as the state flag
+  // is only ever read or written inside the lock.
+  Settings settings;
+
+  // While state == TOOLCHAIN_SETTINGS_LOADING, this will collect all
+  // scheduled invocations using this toolchain. They'll be issued once the
+  // settings file has been interpreted.
+  //
+  // The map maps the source file to "some" location it was invoked from (so
+  // we can give good error messages. It does NOT map to the root of the
+  // file to be invoked (the file still needs loading). This will be NULL
+  // for internally invoked files.
+  typedef std::map<SourceFile, LocationRange> ScheduledInvocationMap;
+  ScheduledInvocationMap scheduled_invocations;
+
+  // Tracks all scheduled and executed invocations for this toolchain. This
+  // is used to avoid invoking a file more than once for a toolchain.
+  std::set<SourceFile> all_invocations;
+
+  // Filled in by EnsureItemNode, see that for more.
+  ItemNode* item_node;
+};
+
+ToolchainManager::ToolchainManager(const BuildSettings* build_settings)
+    : build_settings_(build_settings) {
+}
+
+ToolchainManager::~ToolchainManager() {
+  for (ToolchainMap::iterator i = toolchains_.begin();
+       i != toolchains_.end(); ++i)
+    delete i->second;
+  toolchains_.clear();
+}
+
+void ToolchainManager::StartLoadingUnlocked(const SourceFile& build_file_name) {
+  // How the default build config works: Initially we don't have a toolchain
+  // name to call the settings for the default build config. So we create one
+  // with an empty toolchain name and execute the default build config file.
+  // When that's done, we'll go and fix up the name to the default build config
+  // that the script set.
+  base::AutoLock lock(GetLock());
+  Err err;
+  Info* info = LoadNewToolchainLocked(LocationRange(), Label(), &err);
+  if (err.has_error())
+    g_scheduler->FailWithError(err);
+  CHECK(info);
+  info->scheduled_invocations[build_file_name] = LocationRange();
+  info->all_invocations.insert(build_file_name);
+
+  g_scheduler->IncrementWorkCount();
+  if (!g_scheduler->input_file_manager()->AsyncLoadFile(
+           LocationRange(), build_settings_,
+           build_settings_->build_config_file(),
+           base::Bind(&ToolchainManager::BackgroundLoadBuildConfig,
+                      base::Unretained(this), info, true),
+           &err)) {
+    g_scheduler->FailWithError(err);
+    g_scheduler->DecrementWorkCount();
+  }
+}
+
+const Settings* ToolchainManager::GetSettingsForToolchainLocked(
+    const LocationRange& from_here,
+    const Label& toolchain_name,
+    Err* err) {
+  GetLock().AssertAcquired();
+  ToolchainMap::iterator found = toolchains_.find(toolchain_name);
+  Info* info = NULL;
+  if (found == toolchains_.end()) {
+    info = LoadNewToolchainLocked(from_here, toolchain_name, err);
+    if (!info)
+      return NULL;
+  } else {
+    info = found->second;
+  }
+  info->EnsureItemNode();
+
+  return &info->settings;
+}
+
+const Toolchain* ToolchainManager::GetToolchainDefinitionUnlocked(
+    const Label& toolchain_name) {
+  base::AutoLock lock(GetLock());
+  ToolchainMap::iterator found = toolchains_.find(toolchain_name);
+  if (found == toolchains_.end() || !found->second->toolchain_set)
+    return NULL;
+
+  // Since we don't allow defining a toolchain more than once, we know that
+  // once it's set it won't be mutated, so we can safely return this pointer
+  // for reading outside the lock.
+  return &found->second->toolchain;
+}
+
+bool ToolchainManager::SetDefaultToolchainUnlocked(
+    const Label& default_toolchain,
+    const LocationRange& defined_here,
+    Err* err) {
+  base::AutoLock lock(GetLock());
+  if (!default_toolchain_.is_null()) {
+    *err = Err(defined_here, "Default toolchain already set.");
+    err->AppendSubErr(Err(default_toolchain_defined_here_,
+                          "Previously defined here.",
+                          "You can only set this once."));
+    return false;
+  }
+
+  if (default_toolchain.is_null()) {
+    *err = Err(defined_here, "Bad default toolchain name.",
+        "You can't set the default toolchain name to nothing.");
+    return false;
+  }
+  if (!default_toolchain.toolchain_dir().is_null() ||
+      !default_toolchain.toolchain_name().empty()) {
+    *err = Err(defined_here, "Toolchain name has toolchain.",
+        "You can't specify a toolchain (inside the parens) for a toolchain "
+        "name. I got:\n" + default_toolchain.GetUserVisibleName(true));
+    return false;
+  }
+
+  default_toolchain_ = default_toolchain;
+  default_toolchain_defined_here_ = defined_here;
+  return true;
+}
+
+Label ToolchainManager::GetDefaultToolchainUnlocked() const {
+  base::AutoLock lock(GetLock());
+  return default_toolchain_;
+}
+
+bool ToolchainManager::SetToolchainDefinitionLocked(
+    const Toolchain& tc,
+    const LocationRange& defined_from,
+    Err* err) {
+  GetLock().AssertAcquired();
+
+  ToolchainMap::iterator found = toolchains_.find(tc.label());
+  Info* info = NULL;
+  if (found == toolchains_.end()) {
+    // New toolchain.
+    info = LoadNewToolchainLocked(defined_from, tc.label(), err);
+    if (!info)
+      return false;
+  } else {
+    // It's important to preserve the exact Toolchain object in our tree since
+    // it will be in the ItemTree and targets may have dependencies on it.
+    info = found->second;
+  }
+
+  // The labels should match or else we're setting the wrong one!
+  CHECK(info->toolchain.label() == tc.label());
+
+  info->toolchain = tc;
+  if (info->toolchain_set) {
+    *err = Err(defined_from, "Duplicate toolchain definition.");
+    err->AppendSubErr(Err(
+        info->toolchain_definition_location,
+        "Previously defined here.",
+        "A toolchain can only be defined once. One tricky way that this could\n"
+        "happen is if your definition is itself in a file that's interpreted\n"
+        "under different toolchains, which would result in multiple\n"
+        "definitions as the file is loaded multiple times. So be sure your\n"
+        "toolchain definitions are in files that either don't define any\n"
+        "targets (probably best) or at least don't contain targets executed\n"
+        "with more than one toolchain."));
+    return false;
+  }
+
+  info->EnsureItemNode();
+
+  info->toolchain_set = true;
+  info->toolchain_definition_location = defined_from;
+  return true;
+}
+
+bool ToolchainManager::ScheduleInvocationLocked(
+    const LocationRange& specified_from,
+    const Label& toolchain_name,
+    const SourceDir& dir,
+    Err* err) {
+  GetLock().AssertAcquired();
+  SourceFile build_file(DirToBuildFile(dir));
+
+  ToolchainMap::iterator found = toolchains_.find(toolchain_name);
+  Info* info = NULL;
+  if (found == toolchains_.end()) {
+    // New toolchain.
+    info = LoadNewToolchainLocked(specified_from, toolchain_name, err);
+    if (!info)
+      return false;
+  } else {
+    // Use existing one.
+    info = found->second;
+    if (info->all_invocations.find(build_file) !=
+        info->all_invocations.end()) {
+      // We've already seen this source file for this toolchain, don't need
+      // to do anything.
+      return true;
+    }
+  }
+
+  info->all_invocations.insert(build_file);
+
+  // True if the settings load needs to be scheduled.
+  bool info_needs_settings_load = false;
+
+  // True if the settings load has completed.
+  bool info_settings_loaded = false;
+
+  switch (info->state) {
+    case TOOLCHAIN_SETTINGS_NOT_LOADED:
+      info_needs_settings_load = true;
+      info->scheduled_invocations[build_file] = specified_from;
+      break;
+
+    case TOOLCHAIN_SETTINGS_LOADING:
+      info->scheduled_invocations[build_file] = specified_from;
+      break;
+
+    case TOOLCHAIN_SETTINGS_LOADED:
+      info_settings_loaded = true;
+      break;
+  }
+
+  if (info_needs_settings_load) {
+    // Load the settings file.
+    g_scheduler->IncrementWorkCount();
+    if (!g_scheduler->input_file_manager()->AsyncLoadFile(
+             specified_from, build_settings_,
+             build_settings_->build_config_file(),
+             base::Bind(&ToolchainManager::BackgroundLoadBuildConfig,
+                        base::Unretained(this), info, false),
+             err)) {
+      g_scheduler->DecrementWorkCount();
+      return false;
+    }
+  } else if (info_settings_loaded) {
+    // Settings are ready to go, load the target file.
+    g_scheduler->IncrementWorkCount();
+    if (!g_scheduler->input_file_manager()->AsyncLoadFile(
+             specified_from, build_settings_, build_file,
+             base::Bind(&ToolchainManager::BackgroundInvoke,
+                        base::Unretained(this), info, build_file),
+             err)) {
+      g_scheduler->DecrementWorkCount();
+      return false;
+    }
+  }
+  // Else we should have added the infocations to the scheduled_invocations
+  // from within the lock above.
+  return true;
+}
+
+// static
+std::string ToolchainManager::ToolchainToOutputSubdir(
+    const Label& toolchain_name) {
+  // For now just assume the toolchain name is always a valid dir name. We may
+  // want to clean up the in the future.
+  return toolchain_name.name();
+}
+
+ToolchainManager::Info* ToolchainManager::LoadNewToolchainLocked(
+    const LocationRange& specified_from,
+    const Label& toolchain_name,
+    Err* err) {
+  GetLock().AssertAcquired();
+  Info* info = new Info(build_settings_,
+                        toolchain_name,
+                        ToolchainToOutputSubdir(toolchain_name));
+
+  toolchains_[toolchain_name] = info;
+
+  // Invoke the file containing the toolchain definition so that it gets
+  // defined. The default one (label is empty) will be done spearately.
+  if (!toolchain_name.is_null()) {
+    // The default toolchain should be specified whenever we're requesting
+    // another one. This is how we know under what context we should execute
+    // the invoke for the toolchain file.
+    CHECK(!default_toolchain_.is_null());
+    ScheduleInvocationLocked(specified_from, default_toolchain_,
+                             toolchain_name.dir(), err);
+  }
+  return info;
+}
+
+void ToolchainManager::FixupDefaultToolchainLocked() {
+  // Now that we've run the default build config, we should know the
+  // default toolchain name. Fix up our reference.
+  // See Start() for more.
+  GetLock().AssertAcquired();
+  if (default_toolchain_.is_null()) {
+    g_scheduler->FailWithError(Err(Location(),
+        "Default toolchain not set.",
+        "Your build config file \"" +
+        build_settings_->build_config_file().value() +
+        "\"\ndid not call set_default_toolchain(). This is needed so "
+        "I know how to actually\ncompile your code."));
+    return;
+  }
+
+  ToolchainMap::iterator old_default = toolchains_.find(Label());
+  CHECK(old_default != toolchains_.end());
+  Info* info = old_default->second;
+  toolchains_[default_toolchain_] = info;
+  toolchains_.erase(old_default);
+
+  // Toolchain should not have been loaded in the build config file.
+  CHECK(!info->toolchain_set);
+
+  // We need to set the toolchain label now that we know it. There's no way
+  // to set the label, but we can assign the toolchain to a new one. Loading
+  // the build config can not change the toolchain, so we won't be overwriting
+  // anything useful.
+  info->toolchain = Toolchain(default_toolchain_);
+  info->EnsureItemNode();
+
+  // Schedule a load of the toolchain build file.
+  Err err;
+  ScheduleInvocationLocked(LocationRange(), default_toolchain_,
+                           default_toolchain_.dir(), &err);
+  if (err.has_error())
+    g_scheduler->FailWithError(err);
+}
+
+void ToolchainManager::BackgroundLoadBuildConfig(Info* info,
+                                                 bool is_default,
+                                                 const ParseNode* root) {
+  // Danger: No early returns without decrementing the work count.
+  if (root && !g_scheduler->is_failed()) {
+    // Nobody should be accessing settings at this point other than us since we
+    // haven't marked it loaded, so we can do it outside the lock.
+    Scope* base_config = info->settings.base_config();
+    SetSystemVars(info->settings, base_config);
+    base_config->SetProcessingBuildConfig();
+    if (is_default)
+      base_config->SetProcessingDefaultBuildConfig();
+
+    const BlockNode* root_block = root->AsBlock();
+    Err err;
+    root_block->ExecuteBlockInScope(base_config, &err);
+
+    base_config->ClearProcessingBuildConfig();
+    if (is_default)
+      base_config->ClearProcessingDefaultBuildConfig();
+
+    if (err.has_error()) {
+      g_scheduler->FailWithError(err);
+    } else {
+      // Base config processing succeeded.
+      Info::ScheduledInvocationMap schedule_these;
+      {
+        base::AutoLock lock(GetLock());
+        schedule_these.swap(info->scheduled_invocations);
+        info->state = TOOLCHAIN_SETTINGS_LOADED;
+        if (is_default)
+          FixupDefaultToolchainLocked();
+      }
+
+      // Schedule build files waiting on this settings. There can be many so we
+      // want to load them in parallel on the pool.
+      for (Info::ScheduledInvocationMap::iterator i = schedule_these.begin();
+           i != schedule_these.end() && !g_scheduler->is_failed(); ++i) {
+        // Note i->second may be NULL, so don't dereference.
+        g_scheduler->IncrementWorkCount();
+        if (!g_scheduler->input_file_manager()->AsyncLoadFile(
+                 i->second, build_settings_, i->first,
+                 base::Bind(&ToolchainManager::BackgroundInvoke,
+                            base::Unretained(this), info, i->first),
+                 &err)) {
+          g_scheduler->FailWithError(err);
+          g_scheduler->DecrementWorkCount();
+          break;
+        }
+      }
+    }
+  }
+  g_scheduler->DecrementWorkCount();
+}
+
+void ToolchainManager::BackgroundInvoke(const Info* info,
+                                        const SourceFile& file_name,
+                                        const ParseNode* root) {
+  if (root && !g_scheduler->is_failed()) {
+    if (g_scheduler->verbose_logging())
+      g_scheduler->Log("Running", file_name.value());
+
+    Scope our_scope(info->settings.base_config());
+    ScopePerFileProvider per_file_provider(&our_scope, file_name);
+
+    Err err;
+    root->Execute(&our_scope, &err);
+    if (err.has_error())
+      g_scheduler->FailWithError(err);
+  }
+
+  g_scheduler->DecrementWorkCount();
+}
+
+base::Lock& ToolchainManager::GetLock() const {
+  return build_settings_->item_tree().lock();
+}