From e52d411d60119c8d8cdb2ec2c79b0fb0ef9a2a4f Mon Sep 17 00:00:00 2001
From: andrewlalis <andrewlalisofficial@gmail.com>
Date: Wed, 3 Apr 2024 16:17:20 -0400
Subject: [PATCH] Synchronized DefaultLogHandler writes.

---
 changelogs/3.0.1.md                     |  7 +++++++
 source/slf4d/default_provider/handler.d | 14 ++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)
 create mode 100644 changelogs/3.0.1.md

diff --git a/changelogs/3.0.1.md b/changelogs/3.0.1.md
new file mode 100644
index 0000000..aa1d93e
--- /dev/null
+++ b/changelogs/3.0.1.md
@@ -0,0 +1,7 @@
+# Version 3.0.1
+
+- Added synchronization to the DefaultLogHandler to avoid interleaving messages
+  between the stdout and stderr streams. Each is individually synchronized by
+  the library/system, but both are not synchronized with respect to each other,
+  so errors and info messages may overwrite each other when printed into a
+  single source.
diff --git a/source/slf4d/default_provider/handler.d b/source/slf4d/default_provider/handler.d
index cb99ee3..69ea138 100644
--- a/source/slf4d/default_provider/handler.d
+++ b/source/slf4d/default_provider/handler.d
@@ -35,12 +35,14 @@ class DefaultLogHandler : LogHandler {
     public void handle(immutable LogMessage msg) {
         import std.stdio;
         string logStr = formatLogMessage(msg, this.colored);
-        if (msg.level.value >= Levels.ERROR.value) {
-            stderr.writeln(logStr);
-            stderr.flush();
-        } else {
-            stdout.writeln(logStr);
-            stdout.flush();
+        synchronized(this) {
+            if (msg.level.value >= Levels.ERROR.value) {
+                stderr.writeln(logStr);
+                stderr.flush();
+            } else {
+                stdout.writeln(logStr);
+                stdout.flush();
+            }
         }
     }
 }