Merge pull request #1970 from apple/deterministic-PRNG-in-SwiftPrivate

Author: swift-ci

stdlib/public/stubs/LibcShims.cpp

@@ -66,8 +66,7 @@ size_t _swift_stdlib_malloc_size(const void *ptr) {
 #error No malloc_size analog known for this platform/libc.
 #endif
 
-static std::random_device RandomeDevice;
-static std::mt19937 MersenneRandom(RandomeDevice());
+static std::mt19937 MersenneRandom;
 
 __swift_uint32_t _swift_stdlib_cxx11_mt19937(void) {
   return MersenneRandom();

validation-test/stdlib/Hashing.swift

@@ -1,14 +1,3 @@
-// FIXME: This test fails with some expected probability because
-// it is testing the statistical nature of the hashing.
-// The test failing probabilistically is bad for regression testing,
-// which causes test failures for this test to both be largely
-// ignored but also can cause the entire test suite to fail
-// unexpectedly.
-//
-// This test is being DISABLED until it is written in a way
-// for it to be reliable and useful.
-//
-
 // RUN: %target-run-stdlib-swift
 // REQUIRES: executable_test