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

[Aaron Ballman]

Aside from minor nits, LGTM. Nits below:

> 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

LLVM comments are usually complete sentences (capitalization, period, etc).

> +# 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

I would remove the comment; also, result should be declared to match
rand_s's signature (so unsigned int instead of vanilla unsigned).

> +  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

~Aaron

On Mon, Feb 3, 2014 at 7:03 PM, Stephan Tolksdorf <st at quanttec.com> wrote:
> 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
>
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