From c16b08742738048889192ee3bf10e0635e603646 Mon Sep 17 00:00:00 2001
From: John Ericson <john.ericson@obsidian.systems>
Date: Tue, 26 Nov 2019 21:40:16 -0800
Subject: [PATCH] Work around weird unused errors with Mingw (#6075)

Summary:
From the reset of the code, it looks this this maybe can be unconditionally given the attribute? But I couldn't test with MSVC so I defensively put under CPP.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6075

Differential Revision: D18723749

fbshipit-source-id: 45fc8732c28dd29aab1644225d68f3c6f39bd69b
---
 port/win/io_win.cc     | 7 ++++++-
 port/win/win_thread.cc | 7 ++++++-
 util/status.cc         | 7 ++++++-
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/port/win/io_win.cc b/port/win/io_win.cc
index e050d69ddc..c433e5e522 100644
--- a/port/win/io_win.cc
+++ b/port/win/io_win.cc
@@ -1025,7 +1025,12 @@ Status WinRandomRWFile::Close() {
 //////////////////////////////////////////////////////////////////////////
 /// WinMemoryMappedBufer
 WinMemoryMappedBuffer::~WinMemoryMappedBuffer() {
-  BOOL ret = FALSE;
+  BOOL ret
+#if defined(_MSC_VER)
+    = FALSE;
+#else
+    __attribute__((__unused__));
+#endif
   if (base_ != nullptr) {
     ret = ::UnmapViewOfFile(base_);
     assert(ret);
diff --git a/port/win/win_thread.cc b/port/win/win_thread.cc
index 9a976e2c6b..34e54f3017 100644
--- a/port/win/win_thread.cc
+++ b/port/win/win_thread.cc
@@ -138,7 +138,12 @@ void WindowsThread::join() {
       "WaitForSingleObjectFailed: thread join");
   }
 
-  BOOL rc;
+  BOOL rc
+#if defined(_MSC_VER)
+    = FALSE;
+#else
+    __attribute__((__unused__));
+#endif
   rc = CloseHandle(reinterpret_cast<HANDLE>(data_->handle_));
   assert(rc != 0);
   data_->handle_ = 0;
diff --git a/util/status.cc b/util/status.cc
index 0b1b249353..d75f9271eb 100644
--- a/util/status.cc
+++ b/util/status.cc
@@ -21,7 +21,12 @@ const char* Status::CopyState(const char* state) {
 #ifdef OS_WIN
   const size_t cch = std::strlen(state) + 1;  // +1 for the null terminator
   char* result = new char[cch];
-  errno_t ret;
+  errno_t ret
+#if defined(_MSC_VER)
+    ;
+#else
+    __attribute__((__unused__));
+#endif
   ret = strncpy_s(result, cch, state, cch - 1);
   result[cch - 1] = '\0';
   assert(ret == 0);