tracing: only allow -trace to override -D if set
Otherwise any -D settings the user may have made get ignored.
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Message-Id: <20200225124710.14152-10-alex.bennee@linaro.org>
diff --git a/trace/control.c b/trace/control.c
index 6c775e6..2ffe000 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -226,10 +226,15 @@
#ifdef CONFIG_TRACE_SIMPLE
st_set_trace_file(file);
#elif defined CONFIG_TRACE_LOG
- /* If both the simple and the log backends are enabled, "--trace file"
- * only applies to the simple backend; use "-D" for the log backend.
+ /*
+ * If both the simple and the log backends are enabled, "--trace file"
+ * only applies to the simple backend; use "-D" for the log
+ * backend. However we should only override -D if we actually have
+ * something to override it with.
*/
- qemu_set_log_filename(file, &error_fatal);
+ if (file) {
+ qemu_set_log_filename(file, &error_fatal);
+ }
#else
if (file) {
fprintf(stderr, "error: --trace file=...: "
