core: flush stdout/stderr before forking in hook_process function (closes #1441)

ChangeLog.adoc

@@ -28,6 +28,7 @@ New features::
 
 Bug fixes::
 
+  * core: flush stdout/stderr before forking in hook_process function (issue #1441)
   * core: fix evaluation of condition with nested "if" (issue #1434)
   * irc: case-insensitive comparison on incoming CTCP command, force upper case on CTCP replies (issue #1439)
   * irc: fix memory leak when the channel topic is changed

src/core/hook/wee-hook-process.c

@@ -655,6 +655,10 @@ hook_process_run (struct t_hook *hook_process)
         HOOK_PROCESS(hook_process, child_write[i]) = pipes[i][1];
     }
 
+    /* flush stdout and stderr before forking */
+    fflush (stdout);
+    fflush (stderr);
+
     /* fork */
     switch (pid = fork ())
     {