memory leak

[soldair]

There is a memory leak in the native binding. This simplified test leaks about 3.75mb per 100k lines , but adds up more quickly in relationship to line length.

i traced it to this line
lastSource = shared_ptr<OnigStringContext>(new OnigStringContext(v8String));
https://github.com/atom/node-oniguruma/blob/master/src/onig-scanner.cc#L74
and confirmed the leak happens with a return Nan::Null(); right after. and no leak with the return right before.

reproduction

• run with node --expose_gc --gc_global
• npm install prettyuse oniguruma

var pretty = require('prettyuse')
var oniguruma = require('oniguruma') 
var OnigScanner = oniguruma.OnigScanner
var oscanner = new OnigScanner([])

// excerpt from the marky-markdown readme.
var line  = "  serveImagesWithCDN: false,  // use npm's CDN to proxy images over HTTPS"

for(var i=0;i<=100000;++i){
  oscanner.findNextMatchSync(line+"\n", 0)
  if(!(i%10000)){
    gc()
    console.error('finished ',i,' usage  ',pretty())
  }
}

in heapdumps you can see the leaking strings with no GC roots which points towards a native leak as well. I'm super duper rusty working in native modules so more help would be awesome.

confirmed on node 0.10, 0.12, 2.5, and 4.0
note version ^5.0.0 only compiled for me on node 4 and i used 4.2.2 for earlier versions of node.