Adds a Random class to support --gtest_shuffle (by Josh Kelley); Makes the scons script build in a deterministic order (by Zhanyong Wan).

include/gtest/internal/gtest-internal.h

@@ -748,6 +748,28 @@ String GetCurrentOsStackTraceExceptTop(UnitTest* unit_test, int skip_count);
 // A helper for suppressing warnings on unreachable code in some macros.
 bool AlwaysTrue();
 
+// A simple Linear Congruential Generator for generating random
+// numbers with a uniform distribution.  Unlike rand() and srand(), it
+// doesn't use global state (and therefore can't interfere with user
+// code).  Unlike rand_r(), it's portable.  An LCG isn't very random,
+// but it's good enough for our purposes.
+class Random {
+ public:
+  static const UInt32 kMaxRange = 1u << 31;
+
+  explicit Random(UInt32 seed) : state_(seed) {}
+
+  void Reseed(UInt32 seed) { state_ = seed; }
+
+  // Generates a random number from [0, range).  Crashes if 'range' is
+  // 0 or greater than kMaxRange.
+  UInt32 Generate(UInt32 range);
+
+ private:
+  UInt32 state_;
+  GTEST_DISALLOW_COPY_AND_ASSIGN_(Random);
+};
+
 }  // namespace internal
 }  // namespace testing
 

scons/SConstruct.common

@@ -155,11 +155,6 @@ class SConstructHelper:
                      '/OPT:NOICF',
                      ]
         )
-    # Tell SCons to build depdendencies in random order (apart from the
-    # actual dependency order).  This helps ensure we don't introduce
-    # build files that "accidentally" work sometimes (e.g. when you are
-    # building some targets) and not other times.
-    debug_env.SetOption('random', 1)
     return debug_env
 
   def MakeWinOptimizedEnvironment(self, base_environment, name):

src/gtest.cc

@@ -260,6 +260,25 @@ GTEST_DEFINE_bool_(
 
 namespace internal {
 
+// Generates a random number from [0, range), using a Linear
+// Congruential Generator (LCG).  Crashes if 'range' is 0 or greater
+// than kMaxRange.
+UInt32 Random::Generate(UInt32 range) {
+  // These constants are the same as are used in glibc's rand(3).
+  state_ = (1103515245U*state_ + 12345U) % kMaxRange;
+
+  GTEST_CHECK_(range > 0)
+      << "Cannot generate a number in the range [0, 0).";
+  GTEST_CHECK_(range <= kMaxRange)
+      << "Generation of a number in [0, " << range << ") was requested, "
+      << "but this can only generate numbers in [0, " << kMaxRange << ").";
+
+  // Converting via modulus introduces a bit of downward bias, but
+  // it's simple, and a linear congruential generator isn't too good
+  // to begin with.
+  return state_ % range;
+}
+
 // g_help_flag is true iff the --help flag or an equivalent form is
 // specified on the command line.
 static bool g_help_flag = false;
@@ -3815,7 +3834,7 @@ static void TearDownEnvironment(Environment* env) { env->TearDown(); }
 // considered to be failed, but the rest of the tests will still be
 // run.  (We disable exceptions on Linux and Mac OS X, so the issue
 // doesn't apply there.)
-// When parameterized tests are enabled, it explands and registers
+// When parameterized tests are enabled, it expands and registers
 // parameterized tests first in RegisterParameterizedTests().
 // All other functions called from RunAllTests() may safely assume that
 // parameterized tests are ready to be counted and run.

test/gtest_unittest.cc

@@ -183,6 +183,7 @@ using testing::internal::TestProperty;
 using testing::internal::TestResult;
 using testing::internal::TestResultAccessor;
 using testing::internal::ThreadLocal;
+using testing::internal::UInt32;
 using testing::internal::Vector;
 using testing::internal::WideStringToUtf8;
 using testing::internal::kTestTypeIdInGoogleTest;
@@ -499,6 +500,49 @@ TEST(WideStringToUtf8Test, ConcatenatesCodepointsCorrectly) {
 }
 #endif  // !GTEST_WIDE_STRING_USES_UTF16_
 
+// Tests the Random class.
+
+TEST(RandomDeathTest, GeneratesCrashesOnInvalidRange) {
+  testing::internal::Random random(42);
+  EXPECT_DEATH_IF_SUPPORTED(
+      random.Generate(0),
+      "Cannot generate a number in the range \\[0, 0\\)");
+  EXPECT_DEATH_IF_SUPPORTED(
+      random.Generate(testing::internal::Random::kMaxRange + 1),
+      "Generation of a number in \\[0, 2147483649\\) was requested, "
+      "but this can only generate numbers in \\[0, 2147483648\\)");
+}
+
+TEST(RandomTest, GeneratesNumbersWithinRange) {
+  const UInt32 kRange = 10000;
+  testing::internal::Random random(12345);
+  for (int i = 0; i < 10; i++) {
+    EXPECT_LT(random.Generate(kRange), kRange) << " for iteration " << i;
+  }
+
+  testing::internal::Random random2(testing::internal::Random::kMaxRange);
+  for (int i = 0; i < 10; i++) {
+    EXPECT_LT(random2.Generate(kRange), kRange) << " for iteration " << i;
+  }
+}
+
+TEST(RandomTest, RepeatsWhenReseeded) {
+  const int kSeed = 123;
+  const int kArraySize = 10;
+  const UInt32 kRange = 10000;
+  UInt32 values[kArraySize];
+
+  testing::internal::Random random(kSeed);
+  for (int i = 0; i < kArraySize; i++) {
+    values[i] = random.Generate(kRange);
+  }
+
+  random.Reseed(kSeed);
+  for (int i = 0; i < kArraySize; i++) {
+    EXPECT_EQ(values[i], random.Generate(kRange)) << " for iteration " << i;
+  }
+}
+
 // Tests the Vector class template.
 
 // Tests Vector::Clear().