buffer: don't set kNoZeroFill flag in allocUnsafe

If `kNoZeroFill` is set here, it won't be reset in case of
pooled allocation. In case of "slow" allocation it will be
set later anyway.

Fixes: https://github.com/nodejs/node/issues/6006
PR-URL: https://github.com/nodejs/node/pull/6007
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

lib/buffer.js

@@ -163,8 +163,6 @@ Buffer.alloc = function(size, fill, encoding) {
 Buffer.allocUnsafe = function(size) {
   if (typeof size !== 'number')
     throw new TypeError('"size" argument must be a number');
-  if (size > 0)
-    flags[kNoZeroFill] = 1;
   return allocate(size);
 };
 

test/parallel/test-buffer-safe-unsafe.js

@@ -7,8 +7,18 @@ const safe = Buffer.alloc(10);
 
 function isZeroFilled(buf) {
   for (let n = 0; n < buf.length; n++)
-    if (buf[n] > 0) return false;
+    if (buf[n] !== 0) return false;
   return true;
 }
 
 assert(isZeroFilled(safe));
+
+// Test that unsafe allocations doesn't affect subsequent safe allocations
+Buffer.allocUnsafe(10);
+assert(isZeroFilled(new Float64Array(10)));
+
+new Buffer(10);
+assert(isZeroFilled(new Float64Array(10)));
+
+Buffer.allocUnsafe(10);
+assert(isZeroFilled(Buffer.alloc(10)));