[Patch] Implement sys::Process::GetRandomNumber on Windows

[Stephan Tolksdorf]

Hi,

This is a little patch that implements sys::Process::GetRandomNumber on 
Windows. Currently this function only has a Unix implementation.

The implementation uses the s_rand function, which is available on 
Windows XP and later. It's the same function that libc++ uses for 
implementing random_device on Windows.

- Stephan
-------------- next part --------------
>From b2976da4fc38c9fb41498915af3d6eee8bac7267 Mon Sep 17 00:00:00 2001
From: Stephan Tolksdorf <st at quanttec.com>
Date: Mon, 3 Feb 2014 21:25:01 +0100
Subject: Implement llvm::sys::Process::GetRandomNumber() for Windows

This function was already implemented for Unix. The implementation uses the
rand_s function, which according to MSDN is available on Windows XP and later.
libc++ also uses rand_s for implementing random_device. I've checked
that mingw-w64 supports rand_s.
---
 lib/Support/Process.cpp           | 4 ++++
 lib/Support/Windows/Process.inc   | 7 +++++++
 unittests/Support/ProcessTest.cpp | 6 ++++++
 3 files changed, 17 insertions(+)

diff --git a/lib/Support/Process.cpp b/lib/Support/Process.cpp
index d5168f0..009c7c8 100644
--- a/lib/Support/Process.cpp
+++ b/lib/Support/Process.cpp
@@ -9,12 +9,16 @@
 //
 //  This header file implements the operating system Process concept.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Config/config.h"
+#if LLVM_ON_WIN32
+# define _CRT_RAND_S // makes stdlib.h declare the rand_s function
+# include <stdlib.h>
+#endif
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Process.h"
 
 using namespace llvm;
 using namespace sys;
 
diff --git a/lib/Support/Windows/Process.inc b/lib/Support/Windows/Process.inc
index 750097e..73ce97a 100644
--- a/lib/Support/Windows/Process.inc
+++ b/lib/Support/Windows/Process.inc
@@ -357,6 +357,13 @@ const char *Process::OutputReverse() {
 
 const char *Process::ResetColor() {
   if (UseANSI) return "\033[0m";
   SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE), defaultColors());
   return 0;
 }
+
+unsigned Process::GetRandomNumber() {
+  unsigned result;
+  const errno_t ec = rand_s(&result); // supported in Win XP and later
+  assert(ec == 0 && "rand_s failed");
+  return result;
+}
diff --git a/unittests/Support/ProcessTest.cpp b/unittests/Support/ProcessTest.cpp
index af6a6f9..387d5d3 100644
--- a/unittests/Support/ProcessTest.cpp
+++ b/unittests/Support/ProcessTest.cpp
@@ -36,12 +36,18 @@ TEST(ProcessTest, SelfProcess) {
   EXPECT_LT(TimeValue::MinTime, process::get_self()->get_system_time());
   EXPECT_GT(TimeValue::MaxTime, process::get_self()->get_system_time());
   EXPECT_LT(TimeValue::MinTime, process::get_self()->get_wall_time());
   EXPECT_GT(TimeValue::MaxTime, process::get_self()->get_wall_time());
 }
 
+TEST(ProcessTest, GetRandomNumberTest) {
+  const unsigned r1 = Process::GetRandomNumber();
+  const unsigned r2 = Process::GetRandomNumber();
+  EXPECT_NE((r1 | r2), 0); // 0 should be extremely unlikely
+}
+
 #ifdef _MSC_VER
 #define setenv(name, var, ignore) _putenv_s(name, var)
 #endif
 
 #if HAVE_SETENV || _MSC_VER
 TEST(ProcessTest, Basic) {
-- 
1.7.11.msysgit.1