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Commit cd83df3

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Gabriel SchulhofMylesBorins
Gabriel Schulhof
authored and
MylesBorins
committed
n-api: initialize a module via a special symbol
Much like regular modules, N-API modules can also benefit from having a special symbol which they can expose. Fixes: #19845 PR-URL: #20161 Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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‎doc/api/n-api.md‎

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+26Lines changed: 26 additions & 0 deletions
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Original file line numberDiff line numberDiff line change
@@ -982,6 +982,32 @@ napi_value Init(napi_env env, napi_value exports) {
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}
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```
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If you expect that your module will be loaded multiple times during the lifetime
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of the Node.js process, you can use the `NAPI_MODULE_INIT` macro to initialize
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your module:
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```C
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NAPI_MODULE_INIT() {
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napi_value answer;
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napi_status result;
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status = napi_create_int64(env, 42, &answer);
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if (status != napi_ok) return NULL;
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status = napi_set_named_property(env, exports, "answer", answer);
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if (status != napi_ok) return NULL;
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return exports;
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}
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```
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This macro includes `NAPI_MODULE`, and declares an `Init` function with a
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special name and with visibility beyond the addon. This will allow Node.js to
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initialize the module even if it is loaded multiple times.
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The variables `env` and `exports` will be available inside the function body
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following the macro invocation.
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For more details on setting properties on objects, see the section on
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[Working with JavaScript Properties][].
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‎src/node.cc‎

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+9Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2227,6 +2227,13 @@ inline InitializerCallback GetInitializerCallback(DLib* dlib) {
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return reinterpret_cast<InitializerCallback>(dlib->GetSymbolAddress(name));
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}
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inline napi_addon_register_func GetNapiInitializerCallback(DLib* dlib) {
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const char* name =
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STRINGIFY(NAPI_MODULE_INITIALIZER_BASE) STRINGIFY(NAPI_MODULE_VERSION);
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return
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reinterpret_cast<napi_addon_register_func>(dlib->GetSymbolAddress(name));
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}
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// DLOpen is process.dlopen(module, filename, flags).
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// Used to load 'module.node' dynamically shared objects.
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//
@@ -2283,6 +2290,8 @@ static void DLOpen(const FunctionCallbackInfo<Value>& args) {
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if (mp == nullptr) {
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if (auto callback = GetInitializerCallback(&dlib)) {
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callback(exports, module, context);
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} else if (auto napi_callback = GetNapiInitializerCallback(&dlib)) {
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napi_module_register_by_symbol(exports, module, context, napi_callback);
22862295
} else {
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dlib.Close();
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env->ThrowError("Module did not self-register.");
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‎src/node_api.cc‎

Copy file name to clipboardExpand all lines: src/node_api.cc
+10-5Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -858,16 +858,23 @@ void napi_module_register_cb(v8::Local<v8::Object> exports,
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v8::Local<v8::Value> module,
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v8::Local<v8::Context> context,
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void* priv) {
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napi_module* mod = static_cast<napi_module*>(priv);
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napi_module_register_by_symbol(exports, module, context,
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static_cast<napi_module*>(priv)->nm_register_func);
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}
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} // end of anonymous namespace
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void napi_module_register_by_symbol(v8::Local<v8::Object> exports,
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v8::Local<v8::Value> module,
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v8::Local<v8::Context> context,
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napi_addon_register_func init) {
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// Create a new napi_env for this module or reference one if a pre-existing
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// one is found.
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napi_env env = v8impl::GetEnv(context);
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napi_value _exports;
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NAPI_CALL_INTO_MODULE_THROW(env,
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_exports = mod->nm_register_func(env,
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v8impl::JsValueFromV8LocalValue(exports)));
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_exports = init(env, v8impl::JsValueFromV8LocalValue(exports)));
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// If register function returned a non-null exports object different from
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// the exports object we passed it, set that as the "exports" property of
@@ -879,8 +886,6 @@ void napi_module_register_cb(v8::Local<v8::Object> exports,
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}
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}
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} // end of anonymous namespace
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// Registers a NAPI module.
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void napi_module_register(napi_module* mod) {
886891
node::node_module* nm = new node::node_module {
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‎src/node_api.h‎

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+20-1Lines changed: 20 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -90,9 +90,28 @@ typedef struct {
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} \
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EXTERN_C_END
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#define NAPI_MODULE(modname, regfunc) \
93+
#define NAPI_MODULE(modname, regfunc) \
9494
NAPI_MODULE_X(modname, regfunc, NULL, 0) // NOLINT (readability/null_usage)
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#define NAPI_MODULE_INITIALIZER_BASE napi_register_module_v
97+
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#define NAPI_MODULE_INITIALIZER_X(base, version) \
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NAPI_MODULE_INITIALIZER_X_HELPER(base, version)
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#define NAPI_MODULE_INITIALIZER_X_HELPER(base, version) base##version
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#define NAPI_MODULE_INITIALIZER \
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NAPI_MODULE_INITIALIZER_X(NAPI_MODULE_INITIALIZER_BASE, \
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NAPI_MODULE_VERSION)
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#define NAPI_MODULE_INIT() \
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EXTERN_C_START \
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NAPI_MODULE_EXPORT napi_value \
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NAPI_MODULE_INITIALIZER(napi_env env, napi_value exports); \
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EXTERN_C_END \
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NAPI_MODULE(NODE_GYP_MODULE_NAME, NAPI_MODULE_INITIALIZER) \
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napi_value NAPI_MODULE_INITIALIZER(napi_env env, \
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napi_value exports)
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#define NAPI_AUTO_LENGTH SIZE_MAX
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EXTERN_C_START
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‎src/node_internals.h‎

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+5Lines changed: 5 additions & 0 deletions
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@@ -33,6 +33,7 @@
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#include "tracing/trace_event.h"
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#include "node_perf_common.h"
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#include "node_debug_options.h"
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#include "node_api.h"
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#include <stdint.h>
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#include <stdlib.h>
@@ -840,6 +841,10 @@ static inline const char *errno_string(int errorno) {
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} // namespace node
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void napi_module_register_by_symbol(v8::Local<v8::Object> exports,
845+
v8::Local<v8::Value> module,
846+
v8::Local<v8::Context> context,
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napi_addon_register_func init);
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844849
#endif // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
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‎test/addons-napi/1_hello_world/binding.c‎

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+1-3Lines changed: 1 addition & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -10,10 +10,8 @@ napi_value Method(napi_env env, napi_callback_info info) {
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return world;
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}
1212

13-
napi_value Init(napi_env env, napi_value exports) {
13+
NAPI_MODULE_INIT() {
1414
napi_property_descriptor desc = DECLARE_NAPI_PROPERTY("hello", Method);
1515
NAPI_CALL(env, napi_define_properties(env, exports, 1, &desc));
1616
return exports;
1717
}
18-
19-
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)
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‎test/addons-napi/1_hello_world/test.js‎

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+9-2Lines changed: 9 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,13 @@
11
'use strict';
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const common = require('../../common');
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const assert = require('assert');
4-
const addon = require(`./build/${common.buildType}/binding`);
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const bindingPath = require.resolve(`./build/${common.buildType}/binding`);
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const binding = require(bindingPath);
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assert.strictEqual(binding.hello(), 'world');
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console.log('binding.hello() =', binding.hello());
58

6-
assert.strictEqual(addon.hello(), 'world');
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// Test multiple loading of the same module.
10+
delete require.cache[bindingPath];
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const rebinding = require(bindingPath);
12+
assert.strictEqual(rebinding.hello(), 'world');
13+
assert.notStrictEqual(binding.hello, rebinding.hello);

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