blob: 36c70881a80df059cce7e5ea94ce9438cea58af6 [file] [log] [blame]
// 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/import_manager.h"
#include <memory>
#include "tools/gn/err.h"
#include "tools/gn/parse_tree.h"
#include "tools/gn/scheduler.h"
#include "tools/gn/scope_per_file_provider.h"
#include "tools/gn/trace.h"
#include "util/ticks.h"
namespace {
// Returns a newly-allocated scope on success, null on failure.
std::unique_ptr<Scope> UncachedImport(const Settings* settings,
const SourceFile& file,
const ParseNode* node_for_err,
Err* err) {
ScopedTrace load_trace(TraceItem::TRACE_IMPORT_LOAD, file.value());
const ParseNode* node = g_scheduler->input_file_manager()->SyncLoadFile(
node_for_err->GetRange(), settings->build_settings(), file, err);
if (!node)
return nullptr;
std::unique_ptr<Scope> scope =
// Don't allow ScopePerFileProvider to provide target-related variables.
// These will be relative to the imported file, which is probably not what
// people mean when they use these.
ScopePerFileProvider per_file_provider(scope.get(), false);
node->Execute(scope.get(), err);
if (err->has_error()) {
// If there was an error, append the caller location so the error message
// displays a why the file was imported (esp. useful for failed asserts).
err->AppendSubErr(Err(node_for_err, "whence it was imported."));
return nullptr;
return scope;
} // namespace
struct ImportManager::ImportInfo {
ImportInfo() = default;
~ImportInfo() = default;
// This lock protects the unique_ptr. Once the scope is computed,
// it is const and can be accessed read-only outside of the lock.
std::mutex load_lock;
std::unique_ptr<const Scope> scope;
// The result of loading the import. If the load failed, the scope will be
// null but this will be set to error. In this case the thread should not
// attempt to load the file, even if the scope is null.
Err load_result;
ImportManager::ImportManager() = default;
ImportManager::~ImportManager() = default;
bool ImportManager::DoImport(const SourceFile& file,
const ParseNode* node_for_err,
Scope* scope,
Err* err) {
// Key for the current import on the current thread in imports_in_progress_.
std::stringstream ss;
ss << std::this_thread::get_id() << file.value();
std::string key = ss.str();
// See if we have a cached import, but be careful to actually do the scope
// copying outside of the lock.
ImportInfo* import_info = nullptr;
std::lock_guard<std::mutex> lock(imports_lock_);
std::unique_ptr<ImportInfo>& info_ptr = imports_[file];
if (!info_ptr)
info_ptr = std::make_unique<ImportInfo>();
// Promote the ImportInfo to outside of the imports lock.
import_info = info_ptr.get();
if (imports_in_progress_.find(key) != imports_in_progress_.end()) {
*err = Err(Location(), file.value() + " is part of an import loop.");
return false;
// Now use the per-import-file lock to block this thread if another thread
// is already processing the import.
const Scope* import_scope = nullptr;
Ticks import_block_begin = TicksNow();
std::lock_guard<std::mutex> lock(import_info->load_lock);
if (!import_info->scope) {
// Only load if the import hasn't already failed.
if (!import_info->load_result.has_error()) {
import_info->scope = UncachedImport(
scope->settings(), file, node_for_err, &import_info->load_result);
if (import_info->load_result.has_error()) {
*err = import_info->load_result;
return false;
} else {
// Add trace if this thread was blocked for a long period of time and did
// not load the import itself.
Ticks import_block_end = TicksNow();
constexpr auto kImportBlockTraceThresholdMS = 20;
if (TracingEnabled() &&
TicksDelta(import_block_end, import_block_begin).InMilliseconds() >
kImportBlockTraceThresholdMS) {
auto* import_block_trace =
new TraceItem(TraceItem::TRACE_IMPORT_BLOCK, file.value(),
// Promote the now-read-only scope to outside the load lock.
import_scope = import_info->scope.get();
Scope::MergeOptions options;
options.skip_private_vars = true;
options.mark_dest_used = true; // Don't require all imported values be used.
std::lock_guard<std::mutex> lock(imports_lock_);
return import_scope->NonRecursiveMergeTo(scope, options, node_for_err,
"import", err);
std::vector<SourceFile> ImportManager::GetImportedFiles() const {
std::vector<SourceFile> imported_files;
std::transform(imports_.begin(), imports_.end(), imported_files.begin(),
[](const ImportMap::value_type& val) { return val.first; });
return imported_files;