Changeset 25541 in webkit for trunk/JavaScriptCore/kjs/math_object.cpp

Timestamp:

Sep 13, 2007, 11:52:29 AM (18 years ago)

Author:

ggaren

Message:

2007-09-12 Geoff Garen <​[email protected]>

Reviewed by Sam Weinig.

Fixed <rdar://problem/5429064> 141885 Safari JavaScript: Math.random() slightly less randomly distributed than on Safari / Mac

Math.random was skewed slightly upward because it assumed that RAND_MAX was outside the range of
values that rand() might return. This problem was particularly pronounced on Windows because
the range of values returned by rand() on Windows is 2^{16 smaller than the range of values
return by rand() on Mac.}

Fixed by accounting for RAND_MAX return values. Also, switched Windows over to rand_s, which has
a range that's equal to rand()'s range on Mac.

• kjs/config.h:

• kjs/math_object.cpp: (MathFuncImp::callAsFunction): Use the new new thing.

• wtf/MathExtras.h: Platform abstraction for random numbers, to cover over differences on Windows. (wtf_random_init): (wtf_random):

File:

• trunk/JavaScriptCore/kjs/math_object.cpp (modified) (2 diffs)

trunk/JavaScriptCore/kjs/math_object.cpp

@@ -116 +116 @@
 // ------------------------------ MathObjectImp --------------------------------
 
-static bool randomSeeded = false;
+static bool didInitRandom;
 
 MathFuncImp::MathFuncImp(ExecState* exec, int i, int l, const Identifier& name)
@@ -206 +206 @@
     break;
   case MathObjectImp::Random:
-      if (!randomSeeded) {
-          srand(static_cast<unsigned>(time(0)));
-          randomSeeded = true;
+      if (!didInitRandom) {
+          wtf_random_init();
+          didInitRandom = true;
       }
-      result = (double)rand() / RAND_MAX;
+      result = wtf_random();
       break;
   case MathObjectImp::Round: