Add instant log flush option (#209)

src/common/logging/backend.cpp

@@ -68,7 +68,7 @@ public:
     }
 
     void Flush() override {
-        // stderr shouldn't be buffered
+        std::fflush(stderr);
     }
 
     void EnableForStacktrace() override {
@@ -263,7 +263,14 @@ public:
             !boost::regex_search(FormatLogMessage(new_entry), regex_filter)) {
             return;
         }
-        message_queue.EmplaceWait(new_entry);
+        if (Settings::values.instant_debug_log.GetValue()) {
+            ForEachBackend([&new_entry](Backend& backend) {
+                backend.Write(new_entry);
+                backend.Flush();
+            });
+        } else {
+            message_queue.EmplaceWait(new_entry);
+        }
     }
 
 private:

src/common/settings.cpp

@@ -147,6 +147,7 @@ void LogSettings() {
     log_setting("Debugging_DelayStartForLLEModules", values.delay_start_for_lle_modules.GetValue());
     log_setting("Debugging_UseGdbstub", values.use_gdbstub.GetValue());
     log_setting("Debugging_GdbstubPort", values.gdbstub_port.GetValue());
+    log_setting("Debugging_InstantDebugLog", values.instant_debug_log.GetValue());
 }
 
 bool IsConfiguringGlobal() {

src/common/settings.h

@@ -542,6 +542,7 @@ struct Values {
     Setting<bool> delay_start_for_lle_modules{true, "delay_start_for_lle_modules"};
     Setting<bool> use_gdbstub{false, "use_gdbstub"};
     Setting<u16> gdbstub_port{24689, "gdbstub_port"};
+    Setting<bool> instant_debug_log{false, "instant_debug_log"};
 
     // Miscellaneous
     Setting<std::string> log_filter{"*:Info", "log_filter"};