Now using a std::async and future to do an async popen but I also need the FILE read in read_line to be async, so now I'm at a point where I have to refactor into a better statemachine.

builder.cpp

@@ -19,10 +19,12 @@
 #include <unistd.h>
 #include <nlohmann/json.hpp>
 #include <fstream>
+#include <future>
 
 using std::string;
 using namespace fmt;
 using namespace nlohmann;
+using namespace std::chrono_literals;
 
 #define BUF_MAX 1024
 
@@ -37,6 +39,7 @@ 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;
@@ -80,9 +83,10 @@ MatchResult Builder::parse_line(const string &line) {
 }
 
 enum BuildState {
-  WAITING, BUILDING, DONE
+  WAITING, BUILDING, DONE, STARTING, READING
 };
 
+
 void Builder::run() {
   git_repository* repo = nullptr;
 
@@ -104,7 +108,9 @@ void Builder::run() {
 
     FILE *build_out = NULL;
     bool build_done = false;
+    string line = "";
     BuildState state = WAITING;
+    std::future<FILE *> build_fut;
 
     fileWatcher->watch();
 
@@ -115,15 +121,34 @@ void Builder::run() {
           game.start_round();
           gui.building();
           gui.output(format("CHANGES! Running build {}", build_cmd));
-          build_out = start_command(build_cmd);
+          build_fut = std::async([&]() {
-          state = BUILDING;
+              return start_command(build_cmd);
+          });
+          state = STARTING;
+        }
+      break;
+
+      case STARTING: {
+          println(">>> STARTING");
+          std::future_status status = build_fut.wait_for(0ms);
+
+          if(status == std::future_status::ready) {
+            build_out = build_fut.get();
+            state = READING;
+          } else {
+            state = STARTING;
+          }
         }
         break;
 
+      case READING: {
+          line = read_line(build_out, build_done);
+          state = BUILDING;
+          }
+      break;
       case BUILDING: {
+          println(">>> BUILDING");
           // check if there's output
-          string line = read_line(build_out, build_done);
-
           if(build_done) {
             bool good = end_build(build_out, gui, build_cmd);
 
@@ -143,7 +168,7 @@ void Builder::run() {
               gui.output(format("HIT WITH {} @ {}:{}:{} {}", m.type, m.file_name, m.lnumber, m.col, m.message));
               game.hit(m.type);
             }
-            state = BUILDING;
+            state = READING;
           }
        }
       break;

threadtest.cpp

@@ -1,54 +1,37 @@
-#include <condition_variable>
+#include <chrono>
+#include <future>
 #include <iostream>
-#include <mutex>
-#include <string>
 #include <thread>
+using namespace std::chrono_literals;
 
-std::mutex m;
+int main()
-std::condition_variable cv;
-std::string data;
-bool ready = false;
-bool processed = false;
-
-void worker_thread()
 {
-    // wait until main() sends data
+    std::future<int> future = std::async(std::launch::async, []()
-    std::unique_lock lk(m);
+    {
-    cv.wait(lk, []{ return ready; });
+        std::this_thread::sleep_for(3s);
-
+        return 8;
-    // after the wait, we own the lock
+    });
-    std::cout << "Worker thread is processing data\n";
-    data += " after processing";
-
-    // send data back to main()
-    processed = true;
-    std::cout << "Worker thread signals data processing completed\n";
 
-    // manual unlocking is done before notifying, to avoid waking up
+    std::cout << "waiting...\n";
-    // the waiting thread only to block again (see notify_one for details)
+    std::future_status status;
-    lk.unlock();
-    cv.notify_one();
-}
 
-int main()
+    do
     {
-    std::thread worker(worker_thread);
+        status = future.wait_for(100ms);
-
+        switch (status)
-    data = "Example data";
-    // send data to the worker thread
         {
-        std::lock_guard lk(m);
+            case std::future_status::deferred:
-        ready = true;
+                std::cout << "deferred\n";
-        std::cout << "main() signals data ready for processing\n";
+                break;
+            case std::future_status::timeout:
+                std::cout << "timeout\n";
+                break;
+            case std::future_status::ready:
+                std::cout << "ready!\n";
+                break;
         }
-    cv.notify_one();
-
-    // wait for the worker
-    {
-        std::unique_lock lk(m);
-        cv.wait(lk, []{ return processed; });
     }
-    std::cout << "Back in main(), data = " << data << '\n';
+    while (status != std::future_status::ready);
 
-    worker.join();
+    std::cout << "result is " << future.get() << '\n';
 }