# HG changeset patch
# Parent  fa07f2e1d79fbae648a758b6b1fa4502aa82b53f
Address MinGW-Issue #39658; declare rand_s() function.

* include/stdlib.h: When the user has defined...
[_CRT_RAND_S]: ...this optional feature test macro, and then...
[__MSVCRT_VERSION__ >= __MSVCR80_DLL]: ...either this non-free, or...
[_WIN32_WINNT>=_WIN32_WINNT_VISTA]: ...this system-standard runtime
library version constraint is satisfied, then...
(rand_s): ...declare function prototype.

diff --git a/mingwrt/include/stdlib.h b/mingwrt/include/stdlib.h
--- a/mingwrt/include/stdlib.h
+++ b/mingwrt/include/stdlib.h
@@ -5,11 +5,11 @@
  * associated macros, and manifest constant definitions.
  *
  * $Id$
  *
  * Written by Colin Peters <colin@bird.fu.is.saga-u.ac.jp>
- * Copyright (C) 1997-2009, 2011, 2014-2016, 2018, MinGW.org Project.
+ * Copyright (C) 1997-2009, 2011, 2014-2016, 2018, 2019, MinGW.org Project.
  *
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
@@ -479,10 +479,29 @@ wchar_t *_wfullpath (wchar_t *, const wc
 _CRTIMP __cdecl __MINGW_NOTHROW  int mbtowc (wchar_t *, const char *, size_t);
 
 _CRTIMP __cdecl __MINGW_NOTHROW  int rand (void);
 _CRTIMP __cdecl __MINGW_NOTHROW  void srand (unsigned int);
 
+/* rand() is devoid of entropy, and is thus a mediocre pseudo-random number
+ * generator.  Microsoft do offer a better quality (bogusly dubbed as a more
+ * secure) PRNG, in the guise of rand_s(), but it
+ *
+ *   1) must be explicitly enabled, by user defined feature test macro;
+ */
+#ifdef _CRT_RAND_S
+/*
+ *   2) is not supported on Win9x, nor any WinNT version prior to WinXP;
+ *   3) on WinXP, requires linking with non-free MSVCR80.DLL, or later;
+ *   4) is provided by MSVCRT.DLL, only from Vista onward.
+ */
+#if __MSVCRT_VERSION__ >= __MSVCR80_DLL || _WIN32_WINNT >= _WIN32_WINNT_VISTA
+
+_CRTIMP __cdecl __MINGW_NOTHROW  int rand_s (unsigned int *);
+
+#endif	/* Win-Vista || MSVCR80.DLL || later */
+#endif	/* _CRT_RAND_S enabled */
+
 _CRTIMP __cdecl __MINGW_NOTHROW  void abort (void) __MINGW_ATTRIB_NORETURN;
 _CRTIMP __cdecl __MINGW_NOTHROW  void exit (int) __MINGW_ATTRIB_NORETURN;
 
 /* Note: this is in startup code, not imported directly from the runtime DLL
  */