Allow broker to always restart on Windows when using log_dest file.

Closes #1080. Thanks to lcouz.

ChangeLog.txt

@@ -30,6 +30,8 @@ Broker:
 - Handle mismatched handshakes (e.g. QoS1 PUBLISH with QoS2 reply) properly.
 - Fix spaces not being allowed in the bridge remote_username option. Closes
  #1131.
+- Allow broker to always restart on Windows when using `log_dest file`. Closes
+ #1080.
 
 Library:
 - Fix TLS connections not working over SOCKS.

lib/util_mosq.c

@@ -404,6 +404,21 @@ FILE *mosquitto__fopen(const char *path, const char *mode, bool restrict_read)
  char username[UNLEN + 1];
  int ulen = UNLEN;
  SECURITY_DESCRIPTOR sd;
+ DWORD dwCreationDisposition;
+
+ switch(mode[0]){
+ case 'a':
+ dwCreationDisposition = OPEN_ALWAYS;
+ break;
+ case 'r':
+ dwCreationDisposition = OPEN_EXISTING;
+ break;
+ case 'w':
+ dwCreationDisposition = CREATE_ALWAYS;
+ break;
+ default:
+ return NULL;
+ }
 
  GetUserName(username, &ulen);
  if (!InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION)) {
@@ -424,7 +439,7 @@ FILE *mosquitto__fopen(const char *path, const char *mode, bool restrict_read)
 
  hfile = CreateFile(buf, GENERIC_READ | GENERIC_WRITE, 0,
  &sec,
- CREATE_NEW,
+ dwCreationDisposition,
  FILE_ATTRIBUTE_NORMAL,
  NULL);