From 6425b6e129ff5149d9bf90da79616eb7d930958e Mon Sep 17 00:00:00 2001
From: Lucas Trzesniewski <lucas.trzesniewski@gmail.com>
Date: Thu, 13 Feb 2020 19:06:04 +0100
Subject: [PATCH] [C] Fix aeron_randomised_int32 on Windows (#854)

- rand() was not seeded and always produced the same sequence
 - rand() * INT_MAX would always cause an overflow
 - Use rand_s instead of rand for better randomness
   and to avoid the dependency on a seed
---
 aeron-driver/src/main/c/aeron_driver.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/aeron-driver/src/main/c/aeron_driver.c b/aeron-driver/src/main/c/aeron_driver.c
index dfaf181296..83a41d55d9 100644
--- a/aeron-driver/src/main/c/aeron_driver.c
+++ b/aeron-driver/src/main/c/aeron_driver.c
@@ -32,6 +32,7 @@
 #include "aeron_windows.h"
 #if defined(AERON_COMPILER_MSVC) && defined(AERON_CPU_X64)
 
+    #define _CRT_RAND_S
     #include <io.h>
     #include <direct.h>
     #include <process.h>
@@ -146,9 +147,18 @@ int32_t aeron_randomised_int32()
         fprintf(stderr, "Failed to read from aeron_dev_random (%d): %s\n", errno, strerror(errno));
         exit(EXIT_FAILURE);
     }
-
+#elif defined(AERON_COMPILER_MSVC)
+    uint32_t value;
+    if (0 == rand_s(&value))
+    {
+        memcpy(&result, &value, sizeof(int32_t));
+    }
+    else
+    {
+        result = (int32_t)(rand() / (double)RAND_MAX * INT_MAX);
+    }
 #else
-    result = rand() * INT_MAX;
+    result = (int32_t)(rand() / (double)RAND_MAX * INT_MAX);
 #endif
     return result;
 }