V8 error stack retention

leaky-error.js

// #! node --trace-gc --expose-gc leaky-error.js 

var heapdump = require('heapdump');

function Root() {
  this.exec = function() {
    throw new Error('test');
  };
}

// Attach to global to avoid preemptive GC of data in this module
global.test = new Root();

var errors = global.errors = [];

(function() {
  for (var i = 0; i < 10000; i++) {
    try {
      var root = new Root();
      root.exec();
    } catch (err) {
      errors.push(err);
    }
  }
})();


gc();
gc();
gc();
gc();

// Has 10002 Root instances and ~10000 Error instances
heapdump.writeSnapshot('leaky-error-1.heapsnapshot');

errors.forEach(function(err) {
  err.stack;
});

setTimeout(function() {
  gc();
  gc();
  gc();
  gc();

  // Has 2 Root instances and ~10000 Error instances
  heapdump.writeSnapshot('leaky-error-2.heapsnapshot');
}, 1000);

Nice one... it looks like by default 10 frames are captured and it can be configured by setting stackTraceLimit

If you set this to 0 instead of calling err.stack at that point do the instances still get collected?