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node-api: fix shutdown crashes
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Refs: nodejs/node-addon-api#906

Ensure that finalization is not defered during shutdown.
The env for the addon is deleted immediately after
iterating the list of finalizers to be run. Defering
causes crashes as the finalization uses the already
deleted env.

Signed-off-by: Michael Dawson <mdawson@devrus.com>

PR-URL: #38492
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Gabriel Schulhof <gabrielschulhof@gmail.com>
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mhdawson authored and targos committed Jun 11, 2021
1 parent 88055ab commit 5995221
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Showing 2 changed files with 38 additions and 2 deletions.
31 changes: 31 additions & 0 deletions src/js_native_api_v8.h
Original file line number Diff line number Diff line change
Expand Up @@ -122,6 +122,37 @@ struct napi_env__ {
void* instance_data = nullptr;
};

// This class is used to keep a napi_env live in a way that
// is exception safe versus calling Ref/Unref directly
class EnvRefHolder {
public:
explicit EnvRefHolder(napi_env env) : _env(env) {
_env->Ref();
}

explicit EnvRefHolder(const EnvRefHolder& other): _env(other.env()) {
_env->Ref();
}

EnvRefHolder(EnvRefHolder&& other) {
_env = other._env;
other._env = nullptr;
}

~EnvRefHolder() {
if (_env != nullptr) {
_env->Unref();
}
}

napi_env env(void) const {
return _env;
}

private:
napi_env _env;
};

static inline napi_status napi_clear_last_error(napi_env env) {
env->last_error.error_code = napi_ok;

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9 changes: 7 additions & 2 deletions src/node_api.cc
Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,13 @@ struct node_napi_env__ : public napi_env__ {
}

void CallFinalizer(napi_finalize cb, void* data, void* hint) override {
napi_env env = static_cast<napi_env>(this);
node_env()->SetImmediate([=](node::Environment* node_env) {
// we need to keep the env live until the finalizer has been run
// EnvRefHolder provides an exception safe wrapper to Ref and then
// Unref once the lamba is freed
EnvRefHolder liveEnv(static_cast<napi_env>(this));
node_env()->SetImmediate([=, liveEnv = std::move(liveEnv)]
(node::Environment* node_env) {
napi_env env = liveEnv.env();
v8::HandleScope handle_scope(env->isolate);
v8::Context::Scope context_scope(env->context());
env->CallIntoModule([&](napi_env env) {
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