Refactored out the main_loop so that it's not tightly coupled inside builder, and in the process found I was accidentally copying GUI and GameEngine because Builder wasn't using a &ref for them. Now they don't have a copy constructor to catch that.

builder.cpp

@@ -33,7 +33,6 @@ Builder::Builder(GUI &g, GameEngine &engine)
 }
 
 FILE *start_command(string &build_cmd) {
-  println(">>>>>>>>> start_command {}", build_cmd);
   FILE *build_out = popen(build_cmd.c_str(), "r");
   dbc::check(build_out != nullptr, "Failed to run command.");
   return build_out;
@@ -51,11 +50,6 @@ string read_line(FILE *build_out, bool &done_out) {
   }
 }
 
-bool end_build(FILE *build_out, GUI &gui, string &build_cmd) {
-  int rc = pclose(build_out);
-  return rc == 0;
-}
-
 MatchResult Builder::parse_line(const string &line) {
   std::regex err_re("(.*?):([0-9]+):([0-9]+):\\s*(.*?):\\s*(.*)\n*");
 
@@ -76,24 +70,12 @@ MatchResult Builder::parse_line(const string &line) {
   }
 }
 
-void Builder::run() {
-  int rc = gui.main_loop(game, [&] {
-      event(GO);
-      return 0;
-  });
-
-  if(rc != 0) println("ERROR IN GUI");
-
-  event(QUIT);
-}
-
 void Builder::building(BuildEvent ev) {
-  println(">>> BUILDING");
   // check if there's output
   if(build_done) {
-    bool good = end_build(build_out, gui, build_cmd);
+    int rc = pclose(build_out);
 
-    if(good) {
+    if(rc == 0) {
       gui.build_works();
     } else {
       // BUG: make it not play two sounds

builder.hpp

@@ -29,8 +29,9 @@ enum BuildEvent {
 };
 
 class Builder : DeadSimpleFSM<BuildState, BuildEvent> {
-  GUI gui;
-  GameEngine game;
+  // FOUND BUG: this was interesting, it got copied but the gui kept working until the refactor
+  GUI &gui;
+  GameEngine &game;
   string git_path = "NOT SET";
   string build_cmd = "NOT SET";
   efsw::FileWatcher* fileWatcher = NULL;
@@ -48,8 +49,6 @@ class Builder : DeadSimpleFSM<BuildState, BuildEvent> {
 
   MatchResult parse_line(const string &line);
 
-  void run();
-
   void event(BuildEvent ev) override {
     try {
       if(ev == QUIT) {

escape_turings_tarpit.cpp

@@ -1,4 +1,5 @@
 #include "builder.hpp"
+#include "gui.hpp"
 #include <fmt/core.h>
 
 int main(int argc, char *argv[])
@@ -7,7 +8,7 @@ int main(int argc, char *argv[])
     GameEngine game{100};
 
     auto builder = Builder(gui, game);
-    builder.run();
+    gui.main_loop(game, builder);
 
     return 1;
 }

fsm.hpp

@@ -3,7 +3,7 @@
 #include <fmt/core.h>
 
 #define FSM_EV(S, F) case S: F(); break
-#define FSM_STATE(S, F, E) case S: fmt::println(">>> " #S ":" #F ":{}", int(E)); F(E); break
+#define FSM_STATE(S, F, E) case S: F(E); break
 
 template<typename S, typename E>
 class DeadSimpleFSM {

game_engine.hpp

@@ -23,6 +23,9 @@ class GameEngine {
 
   GameEngine(int hp);
 
+  // FOUND BUG: I was accidentally copying this and shouldn't have been
+  GameEngine(GameEngine &g) = delete;
+
   int determine_damage(string &type);
 
   void start_round();

gui.cpp

@@ -9,6 +9,7 @@
 #include <nlohmann/json.hpp>
 #include <fstream>
 #include "sfmlgui.hpp"
+#include "builder.hpp"
 
 using std::string, std::vector;
 
@@ -46,22 +47,24 @@ GUI::GUI() {
   building_sound.load(data, "building");
 }
 
-void GUI::output(const string &msg) {
-  lines.push_back(msg);
+void GUI::output(const string msg) {
+  _lines.push_back(msg);
 }
 
-int GUI::main_loop(GameEngine &game, std::function<bool()> runner) {
+int GUI::main_loop(GameEngine &game, Builder &builder) {
   auto gui = SFMLGui(game);
 
   gui.startup();
 
   while(gui.is_open()) {
-    bool result = runner();
+    builder.event(BuildEvent::GO);
     gui.handle_events();
     gui.update_entities();
-    gui.update_log(lines);
+    gui.update_log(_lines);
   }
 
+  builder.event(BuildEvent::QUIT);
+
   gui.shutdown();
   return EXIT_SUCCESS;
 }

gui.hpp

@@ -9,6 +9,8 @@
 
 using std::string;
 
+class Builder;
+
 class SoundQuip {
 public:
   sf::Sound sound;
@@ -23,7 +25,7 @@ public:
 };
 
 class GUI {
-  std::vector<string> lines;
+  std::vector<string> _lines;
 
   SoundQuip you_died_sound;
   SoundQuip build_works_sound;
@@ -34,9 +36,12 @@ class GUI {
 
   GUI();
 
-  void output(const string &msg);
+  // FOUND BUG: adding this found that I was accidentally copying the gui, really it shouldn't be copyable
+  GUI(GUI &g) = delete;
+
+  void output(const string msg);
 
-  int main_loop(GameEngine &game, std::function<bool()> runner);
+  int main_loop(GameEngine &game, Builder &builder);
 
   void build_works();
   void build_failed(bool play_sound, const string &command);