text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2019 The Bitcoin Core developers
  // Copyright (c) 2021 The Shirecoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <support/cleanse.h>
  
  #include <cstring>
  
  #if defined(_MSC_VER)
  #include <Windows.h> // For SecureZeroMemory.
  #endif
  
  void memory_cleanse(void *ptr, size_t len)
  {
  #if defined(_MSC_VER)
      /* SecureZeroMemory is guaranteed not to be optimized out by MSVC. */
      SecureZeroMemory(ptr, len);
  #else
      std::memset(ptr, 0, len);
  
      /* Memory barrier that scares the compiler away from optimizing out the memset.
       *
       * Quoting Adam Langley <agl@google.com> in commit ad1907fe73334d6c696c8539646c21b11178f20f
       * in BoringSSL (ISC License):
       *    As best as we can tell, this is sufficient to break any optimisations that
       *    might try to eliminate "superfluous" memsets.
       * This method is used in memzero_explicit() the Linux kernel, too. Its advantage is that it
       * is pretty efficient because the compiler can still implement the memset() efficiently,
       * just not remove it entirely. See "Dead Store Elimination (Still) Considered Harmful" by
       * Yang et al. (USENIX Security 2017) for more background.
       */
      __asm__ __volatile__("" : : "r"(ptr) : "memory");
  #endif
  }
  