From f178159fba0d0779bd6102248c6f8c7064bd575d Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Mon, 3 Aug 2020 11:47:45 +1000
Subject: [PATCH] log: prefer once_flag over an atomic<bool>

---
 log/log.cpp | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/log/log.cpp b/log/log.cpp
index 70e90bc3..b4e2096d 100644
--- a/log/log.cpp
+++ b/log/log.cpp
@@ -47,7 +47,7 @@ cruft::log::needs_break (level_t level)
 ///////////////////////////////////////////////////////////////////////////////
 // mingw#xxx: MinGW doesn't have once_flag so we just use an atomic bool.
 // Pray that multiple threads don't run into an issue here.
-static std::atomic<bool> s_sink_init;
+static std::once_flag s_sink_init;
 static std::unique_ptr<cruft::log::sink::base> s_default_sink;
 
 
@@ -64,7 +64,7 @@ cruft::log::default_sink (std::unique_ptr<sink::base> value)
 cruft::log::sink::base&
 cruft::log::default_sink ()
 {
-    if (unlikely (!s_sink_init)) {
+    std::call_once (s_sink_init, [&] () {
         static char const *DEFAULT_SINK = "CONSOLE";
         char const *log_sink = getenv ("CRUFT_LOG_SINK") ?: DEFAULT_SINK;
 
@@ -76,9 +76,7 @@ cruft::log::default_sink ()
             std::clog << "Unknown logging sink. Falling back to console.\n";
             default_sink (std::make_unique<sink::console> (PACKAGE_NAME));
         }
-
-        s_sink_init = true;
-    }
+    });
 
     return *s_default_sink;
 }