From 2a2cb0310baac013dde63c5e651f3cfc363a1780 Mon Sep 17 00:00:00 2001
From: "Roger A. Light" <roger@atchoo.org>
Date: Tue, 17 Nov 2020 11:06:20 +0000
Subject: [PATCH] Fix file logging on Windows.

Closes #1880. Thanks to J1EXA, richl, and EnneiteZer.
---
 ChangeLog.txt | 1 +
 src/logging.c | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.txt b/ChangeLog.txt
index f6ccf7b4..f79bcee0 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -3,6 +3,7 @@ Broker:
 - Fix listener not being reassociated with client when reloading a persistence
   file and `per_listener_settings true` is set and the client did not set a
   username. Closes #1891.
+- Fix file logging on Windows. Closes #1880.
 
 
 1.6.12 - 2020-08-19
diff --git a/src/logging.c b/src/logging.c
index ac079a85..52afadc9 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -39,6 +39,8 @@ extern struct mosquitto_db int_db;
 HANDLE syslog_h;
 #endif
 
+static char log_fptr_buffer[BUFSIZ];
+
 /* Options for logging should be:
  *
  * A combination of:
@@ -135,7 +137,7 @@ int log__init(struct mosquitto__config *config)
 		}
 		config->log_fptr = mosquitto__fopen(config->log_file, "at", true);
 		if(config->log_fptr){
-			setvbuf(config->log_fptr, NULL, _IOLBF, 0);
+			setvbuf(config->log_fptr, log_fptr_buffer, _IOLBF, sizeof(log_fptr_buffer));
 		}else{
 			log_destinations = MQTT3_LOG_STDERR;
 			log_priorities = MOSQ_LOG_ERR;
@@ -345,6 +347,10 @@ int log__vprintf(int priority, const char *fmt, va_list va)
 			}else{
 				fprintf(log_fptr, "%s\n", s);
 			}
+#ifdef WIN32
+			/* Windows does support line buffering, so flush. */
+			fflush(log_fptr);
+#endif
 		}
 		if(log_destinations & MQTT3_LOG_SYSLOG){
 #ifndef WIN32