Making progress on util::dprintf

luprex/cpp/drv/driver-common.cpp

@@ -9,6 +9,11 @@ static void if_error_print_and_exit(const std::string_view str) {
     }
 }
 
+static void dprintf_callback(const char *oneline) {
+    fprintf(stderr, "DPRINTF: %s\n", oneline);
+    fflush(stderr);
+}
+
 class Driver {
    public:
     enum ChanState {
@@ -536,6 +541,7 @@ class Driver {
         // Load the DLL and gain access to its functions.
         call_init_engine_wrapper(&engw);
         engw.replay_cb_sent_outgoing = replay_cb_sent_outgoing;
+        engw.hook_dprintf(dprintf_callback);
 
         // If argv contains "replay <filename>", do a replay,
         // and then skip everything else.