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tools: implement node_mksnapshot
Implements a node_mksnapshot target that generates a snapshot blob from a Node.js main instance's isolate, and serializes the data blob with other additional data into a C++ file that can be embedded into the Node.js binary. PR-URL: #27321 Refs: #17058 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Refael Ackermann <refack@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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‎Makefile‎

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@@ -1226,6 +1226,8 @@ LINT_CPP_FILES = $(filter-out $(LINT_CPP_EXCLUDE), $(wildcard \
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tools/icu/*.h \
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tools/code_cache/*.cc \
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tools/code_cache/*.h \
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tools/snapshot/*.cc \
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tools/snapshot/*.h \
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))
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# Code blocks don't have newline at the end,

‎node.gyp‎

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}],
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],
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}, # mkcodecache
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], # end targets
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{
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'target_name': 'node_mksnapshot',
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'type': 'executable',
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'dependencies': [
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'<(node_lib_target_name)',
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'deps/histogram/histogram.gyp:histogram',
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],
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'includes': [
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'node.gypi'
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],
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'include_dirs': [
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'src',
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'tools/msvs/genfiles',
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'deps/v8/include',
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'deps/cares/include',
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'deps/uv/include',
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],
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'defines': [ 'NODE_WANT_INTERNALS=1' ],
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'sources': [
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'src/node_code_cache_stub.cc',
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'tools/snapshot/node_mksnapshot.cc',
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'tools/snapshot/snapshot_builder.cc',
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'tools/snapshot/snapshot_builder.h',
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],
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'conditions': [
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[ 'node_report=="true"', {
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'conditions': [
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['OS=="win"', {
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'libraries': [ 'Ws2_32' ],
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}],
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],
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}],
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],
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}, # node_mksnapshot
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], # end targets
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'conditions': [
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['OS=="aix" and node_shared=="true"', {

‎tools/snapshot/node_mksnapshot.cc‎

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#include <cstdio>
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#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <string>
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#include <vector>
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#include "libplatform/libplatform.h"
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#include "node_internals.h"
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#include "snapshot_builder.h"
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#include "v8.h"
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#ifdef _WIN32
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#include <windows.h>
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int wmain(int argc, wchar_t* argv[]) {
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#else // UNIX
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int main(int argc, char* argv[]) {
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#endif // _WIN32
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if (argc < 2) {
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std::cerr << "Usage: " << argv[0] << " <path/to/output.cc>\n";
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return 1;
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}
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std::ofstream out;
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out.open(argv[1], std::ios::out | std::ios::binary);
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if (!out.is_open()) {
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std::cerr << "Cannot open " << argv[1] << "\n";
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return 1;
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}
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int node_argc = 1;
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char argv0[] = "node";
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char* node_argv[] = {argv0, nullptr};
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node::InitializationResult result =
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node::InitializeOncePerProcess(node_argc, node_argv);
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CHECK(!result.early_return);
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CHECK_EQ(result.exit_code, 0);
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{
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std::string snapshot =
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node::SnapshotBuilder::Generate(result.args, result.exec_args);
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out << snapshot;
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out.close();
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}
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node::TearDownOncePerProcess();
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return 0;
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}

‎tools/snapshot/snapshot_builder.cc‎

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#include "snapshot_builder.h"
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#include <iostream>
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#include <sstream>
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#include "env-inl.h"
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#include "node_internals.h"
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#include "node_main_instance.h"
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#include "node_v8_platform-inl.h"
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namespace node {
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using v8::Context;
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using v8::HandleScope;
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using v8::Isolate;
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using v8::Local;
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using v8::Locker;
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using v8::SnapshotCreator;
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using v8::StartupData;
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std::string FormatBlob(v8::StartupData* blob,
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const std::vector<size_t>& isolate_data_indexes) {
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std::stringstream ss;
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size_t isolate_data_indexes_size = isolate_data_indexes.size();
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ss << R"(#include <cstddef>
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#include "node_main_instance.h"
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#include "v8.h"
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// This file is generated by tools/snapshot. Do not edit.
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namespace node {
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static const uint8_t blob_data[] = {
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)";
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for (int i = 0; i < blob->raw_size; i++) {
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uint8_t ch = blob->data[i];
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ss << std::to_string(ch) << ((i == blob->raw_size - 1) ? '\n' : ',');
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}
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ss << R"(};
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static const int blob_size = )"
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<< blob->raw_size << R"(;
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static v8::StartupData blob = {
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reinterpret_cast<const char*>(blob_data),
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blob_size
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};
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)";
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ss << R"(v8::StartupData*
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NodeMainInstance::GetEmbeddedSnapshotBlob() {
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return &blob;
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}
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static const size_t isolate_data_indexes_raw[] = {
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)";
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for (size_t i = 0; i < isolate_data_indexes_size; i++) {
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ss << std::to_string(isolate_data_indexes[i])
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<< ((i == isolate_data_indexes_size - 1) ? '\n' : ',');
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}
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ss << "};\n\n";
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ss << "static const size_t isolate_data_indexes_size = "
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<< isolate_data_indexes_size << R"(;
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NodeMainInstance::IndexArray isolate_data_indexes {
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isolate_data_indexes_raw,
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isolate_data_indexes_size
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};
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const NodeMainInstance::IndexArray*
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NodeMainInstance::GetIsolateDataIndexes() {
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return &isolate_data_indexes;
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}
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} // namespace node
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)";
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return ss.str();
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}
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std::string SnapshotBuilder::Generate(
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const std::vector<std::string> args,
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const std::vector<std::string> exec_args) {
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// TODO(joyeecheung): collect external references and set it in
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// params.external_references.
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std::vector<intptr_t> external_references = {
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reinterpret_cast<intptr_t>(nullptr)};
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Isolate* isolate = Isolate::Allocate();
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per_process::v8_platform.Platform()->RegisterIsolate(isolate,
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uv_default_loop());
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NodeMainInstance* main_instance = nullptr;
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std::string result;
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{
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std::vector<size_t> isolate_data_indexes;
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SnapshotCreator creator(isolate, external_references.data());
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{
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main_instance =
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NodeMainInstance::Create(isolate,
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uv_default_loop(),
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per_process::v8_platform.Platform(),
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args,
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exec_args);
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HandleScope scope(isolate);
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creator.SetDefaultContext(Context::New(isolate));
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isolate_data_indexes = main_instance->isolate_data()->Serialize(&creator);
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}
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// Must be out of HandleScope
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StartupData blob =
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creator.CreateBlob(SnapshotCreator::FunctionCodeHandling::kClear);
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// Must be done while the snapshot creator isolate is entered i.e. the
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// creator is still alive.
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main_instance->Dispose();
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result = FormatBlob(&blob, isolate_data_indexes);
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delete blob.data;
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}
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per_process::v8_platform.Platform()->UnregisterIsolate(isolate);
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return result;
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}
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} // namespace node

‎tools/snapshot/snapshot_builder.h‎

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#ifndef TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_
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#define TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_
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#include <string>
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#include <vector>
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namespace node {
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class SnapshotBuilder {
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public:
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static std::string Generate(const std::vector<std::string> args,
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const std::vector<std::string> exec_args);
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};
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} // namespace node
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#endif // TOOLS_SNAPSHOT_SNAPSHOT_BUILDER_H_

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