From b626703de7ece507f360507e49d3ecb448b12e07 Mon Sep 17 00:00:00 2001
From: Maysam Yabandeh <myabandeh@fb.com>
Date: Thu, 12 Dec 2019 13:48:50 -0800
Subject: [PATCH] Fix build breakage from lock_guard error (#6161)

Summary:
This change fixes a source issue that caused compile time error which breaks build for many fbcode services in that setup. The size() member function of channel is a const member, so member variables accessed within it are implicitly const as well. This caused error when clang fails to resolve to a constructor that takes std::mutex because the suitable constructor got rejected due to loss of constness for its argument. The fix is to add mutable modifier to the lock_ member of channel.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6161

Differential Revision: D18967685

Pulled By: maysamyabandeh

Upstream-Status: Backport

fbshipit-source-id: 698b6a5153c3c92eeacb842c467aa28cc350d432
---
 util/channel.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/channel.h b/util/channel.h
index 0225482c0..a8a47680a 100644
--- a/util/channel.h
+++ b/util/channel.h
@@ -60,7 +60,7 @@ class channel {
 
  private:
   std::condition_variable cv_;
-  std::mutex lock_;
+  mutable std::mutex lock_;
   std::queue<T> buffer_;
   bool eof_;
 };
-- 
2.24.1