log: Redirect stderr to logfile if deamonized

In case of daemonize, use the logfile passed with the -D option in
order to redirect stderr to it instead of /dev/null.

Also remove some unused code in log.h.

Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Message-Id: <1455795518-19205-1-git-send-email-dimara@arrikto.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/os-posix.c b/os-posix.c
index cce62ed..92fa3ba 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -37,6 +37,7 @@
 #include "qemu-options.h"
 #include "qemu/rcu.h"
 #include "qemu/error-report.h"
+#include "qemu/log.h"
 
 #ifdef CONFIG_LINUX
 #include <sys/prctl.h>
@@ -275,7 +276,10 @@
 
         dup2(fd, 0);
         dup2(fd, 1);
-        dup2(fd, 2);
+        /* In case -D is given do not redirect stderr to /dev/null */
+        if (!qemu_logfile) {
+            dup2(fd, 2);
+        }
 
         close(fd);