Create Local handle for new Buffers to avoid GC

[rvagg]

fixes #19

The lack of a Local handle inside the HandleScope where the new Buffer objects are being created means that the GC can kick in while you're still working on them and clean up the handles that were originally created for them. This change introduces explicit handles each time you Buffer::New() which will automatically be assigned to the HandleScope in use.

[jedisct1]

👍

[trevnorris]

Wow, forgot how ugly the Buffer API is in 0.10.

Also, Buffer::New(size) doesn't zero fill the memory. So it's possible to have random bytes wandering around in the allocated memory. Don't know the code that we'll, but are you writing to the entire Buffer or just part of it.

[trevnorris]

@rvagg I'm pretty sure name->handle_ is a Persistent which implies it lives outside the life cycle of the HandleScope. So I'm missing why the creation of a Local would fix the problem.

[rvagg]

it's a weak Persistent https://github.com/joyent/node/blob/v0.10.29-release/src/node_object_wrap.h#L68-L75

[warner]

I can confirm that this patch fixes the corruption problem I saw in #19, at least it made it through 10M cycles whereas before I was seeing corruption after only a few thousand. I know nothing about the memory-lifetime tools here, but memory usage appears stable, so I don't think it's keeping the memory around forever.

[rvagg]

the addition shouldn't have any impact on memory: Local handles only increase the reference count of an object within the HandleScope for which it is created, outside of that it's free to be garbage collected if the count drops to zero. Buffer objects have an implicit Persistent reference from Node's ObjectWrap which floats free of HandleScopes but it's marked as weak when you first "wrap" an object so it's effectively up for grabs for garbage collection as soon as it has no references.

[paixaop]

Thank you for the fix. this bug was hunting me for some time now.