DETERMINISTIC option

3 files changed, 10 insertions, 3 deletions

diff --git a/src/determinstic.js b/src/deterministic.js
index 1ec0bbfe..4e9508f3 100644
--- a/src/determinstic.js
+++ b/src/deterministic.js
@@ -8,13 +8,14 @@ var TIME = 10000;
 Date.now = function() {
   return TIME++;
 };
-performance.now = Date.now;
+if (typeof performance === 'object') performance.now = Date.now;
 
 function hashMemory(id) {
   var ret = 0;
-  for (var i = 0; i < HEAPU8.length; i++) {
+  var len = Math.max(DYNAMICTOP, STATICTOP);
+  for (var i = 0; i < len; i++) {
     ret = (ret*17 + HEAPU8[i])|0;
   }
-  print(id + ':' + ret);
+  printErr(id + ':' + ret);
 }
 
diff --git a/src/jsifier.js b/src/jsifier.js
index 791273f4..a7a53803 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -1901,6 +1901,9 @@ function JSify(data, functionsOnly) {
     if (PROXY_TO_WORKER) {
       print(read('proxyWorker.js'));
     }
+    if (DETERMINISTIC) {
+      print(read('deterministic.js'));
+    }
     if (RUNTIME_TYPE_INFO) {
       Types.cleanForRuntime();
       print('Runtime.typeInfo = ' + JSON.stringify(Types.types));
diff --git a/src/settings.js b/src/settings.js
index a8761d90..26883051 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -478,6 +478,9 @@ var HEADLESS = 0; // If 1, will include shim code that tries to 'fake' a browser
                   // very partial - it is hard to fake a whole browser! - so
                   // keep your expectations low for this to work.
 
+var DETERMINISTIC = 0; // If 1, we force Date.now(), Math.random, etc. to return deterministic
+                       // results. Good for comparing builds for debugging purposes (and nothing else)
+
 var BENCHMARK = 0; // If 1, will just time how long main() takes to execute, and not
                    // print out anything at all whatsoever. This is useful for benchmarking.