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doc: add documentation for AtExit hook
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Fixes: #999
PR-URL: #1014
Reviewed-By: Ben Noordhuis <[email protected]>
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OpenSourceSteve authored and bnoordhuis committed May 26, 2015
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68 changes: 68 additions & 0 deletions doc/api/addons.markdown
Original file line number Diff line number Diff line change
Expand Up @@ -811,3 +811,71 @@ Test it with:
var result = addon.add(obj1, obj2);

console.log(result); // 30

### AtExit hooks
#### void AtExit(callback, args)

* `callback`: `void (*)(void*)` - A pointer to the function to call at exit.
* `args`: `void*` - A pointer to pass to the callback at exit.

Registers exit hooks that run after the event loop has ended, but before the VM
is killed.

Callbacks are run in last-in, first-out order. AtExit takes two parameters:
a pointer to a callback function to run at exit, and a pointer to untyped
context data to be passed to that callback.

The file `addon.cc` implements AtExit below:

// addon.cc
#undef NDEBUG
#include <assert.h>
#include <stdlib.h>
#include <node.h>

namespace demo {

using node::AtExit;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;

static char cookie[] = "yum yum";
static int at_exit_cb1_called = 0;
static int at_exit_cb2_called = 0;

static void at_exit_cb1(void* arg) {
Isolate* isolate = static_cast<Isolate*>(arg);
HandleScope scope(isolate);
Local<Object> obj = Object::New(isolate);
assert(!obj.IsEmpty()); // assert VM is still alive
assert(obj->IsObject());
at_exit_cb1_called++;
}

static void at_exit_cb2(void* arg) {
assert(arg == static_cast<void*>(cookie));
at_exit_cb2_called++;
}

static void sanity_check(void*) {
assert(at_exit_cb1_called == 1);
assert(at_exit_cb2_called == 2);
}

void init(Local<Object> exports) {
AtExit(sanity_check);
AtExit(at_exit_cb2, cookie);
AtExit(at_exit_cb2, cookie);
AtExit(at_exit_cb1, exports->GetIsolate());
}

NODE_MODULE(addon, init);

} // namespace demo

Test in JavaScript by running:

// test.js
var addon = require('./build/Release/addon');

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