src: add context-aware init macro and doc

Introduces macros `NODE_MODULE_INITIALIZER` which expands to the name
of the special symbol that process.dlopen() will look for to initialize
an addon, and `NODE_MODULE_INIT()` which creates the boilerplate for
a context-aware module which can be loaded multiple times via the
special symbol mechanism.

Additionally, provides an example of using the new macro to construct
an addon which stores per-addon-instance data in a heap-allocated
structure that gets passed to each binding, rather than in a collection
of global static variables.

Re: https://github.com/nodejs/node/issues/21291#issuecomment-396729727
PR-URL: https://github.com/nodejs/node/pull/21318
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>

1 files changed, 6 insertions, 7 deletions

diff --git a/test/addons/hello-world/binding.cc b/test/addons/hello-world/binding.cc
index e267a3b2a7..341b58f9a6 100644
--- a/test/addons/hello-world/binding.cc
+++ b/test/addons/hello-world/binding.cc
@@ -6,13 +6,12 @@ void Method(const v8::FunctionCallbackInfo<v8::Value>& args) {
   args.GetReturnValue().Set(v8::String::NewFromUtf8(isolate, "world"));
 }
 
-#define CONCAT(a, b) CONCAT_HELPER(a, b)
-#define CONCAT_HELPER(a, b) a##b
-#define INITIALIZER CONCAT(node_register_module_v, NODE_MODULE_VERSION)
-
-extern "C" NODE_MODULE_EXPORT void INITIALIZER(v8::Local<v8::Object> exports,
-                                               v8::Local<v8::Value> module,
-                                               v8::Local<v8::Context> context) {
+// Not using the full NODE_MODULE_INIT() macro here because we want to test the
+// addon loader's reaction to the FakeInit() entry point below.
+extern "C" NODE_MODULE_EXPORT void
+NODE_MODULE_INITIALIZER(v8::Local<v8::Object> exports,
+                        v8::Local<v8::Value> module,
+                        v8::Local<v8::Context> context) {
   NODE_SET_METHOD(exports, "hello", Method);
 }