Improve exit logic. NFC.

- Don't call `exitRuntime()` when `ENVIRONMENT_IS_PTHREAD` is true.
- Only obtain `runtimeKeepaliveCounter` when `EXIT_RUNTIME` is true.
- Remove the early return from `exitRuntime()`.
- Collapse if/else statements in `exit()`.

Author: kleisauke

src/postamble.js

@@ -411,24 +411,25 @@ function exit(status, implicit) {
 #endif // ASSERTIONS && !EXIT_RUNTIME
 
 #if USE_PTHREADS
-  if (!implicit) {
-    if (ENVIRONMENT_IS_PTHREAD) {
-#if PTHREADS_DEBUG
-      err('Pthread 0x' + _pthread_self().toString(16) + ' called exit(), posting exitOnMainThread.');
-#endif
-      // When running in a pthread we propagate the exit back to the main thread
-      // where it can decide if the whole process should be shut down or not.
-      // The pthread may have decided not to exit its own runtime, for example
-      // because it runs a main loop, but that doesn't affect the main thread.
-      exitOnMainThread(status);
-      throw 'unwind';
-    } else {
+  if (ENVIRONMENT_IS_PTHREAD) {
+#if ASSERTIONS
+    assert(!implicit, "exit should never be called implicitly in a pthread");
+#endif
 #if PTHREADS_DEBUG
-      err('main thread called exit: keepRuntimeAlive=' + keepRuntimeAlive() + ' (counter=' + runtimeKeepaliveCounter + ')');
+    err('Pthread 0x' + _pthread_self().toString(16) + ' called exit(), posting exitOnMainThread.');
+#endif
+    // When running in a pthread we propagate the exit back to the main thread
+    // where it can decide if the whole process should be shut down or not.
+    // The pthread may have decided not to exit its own runtime, for example
+    // because it runs a main loop, but that doesn't affect the main thread.
+    exitOnMainThread(status);
+    throw 'unwind';
+#if EXIT_RUNTIME && PTHREADS_DEBUG
+  } else if (!implicit) {
+    err('main thread called exit: keepRuntimeAlive=' + keepRuntimeAlive() + ' (counter=' + runtimeKeepaliveCounter + ')');
 #endif
-    }
   }
-#endif
+#endif // USE_PTHREADS
 
 #if EXIT_RUNTIME
   if (!keepRuntimeAlive()) {
@@ -437,12 +438,13 @@ function exit(status, implicit) {
 #endif
 
 #if ASSERTIONS
+#if EXIT_RUNTIME
   // if exit() was called explicitly, warn the user if the runtime isn't actually being shut down
+  else if (!implicit) {
+    var msg = 'program exited (with status: ' + status + '), but keepRuntimeAlive() is set (counter=' + runtimeKeepaliveCounter + ') due to an async operation, so halting execution but not exiting the runtime or preventing further async execution (you can use emscripten_force_exit, if you want to force a true shutdown)';
+#else // !EXIT_RUNTIME
   if (keepRuntimeAlive() && !implicit) {
-#if !EXIT_RUNTIME
     var msg = 'program exited (with status: ' + status + '), but EXIT_RUNTIME is not set, so halting execution but not exiting the runtime or preventing further async execution (build with EXIT_RUNTIME=1, if you want a true shutdown)';
-#else
-    var msg = 'program exited (with status: ' + status + '), but keepRuntimeAlive() is set (counter=' + runtimeKeepaliveCounter + ') due to an async operation, so halting execution but not exiting the runtime or preventing further async execution (you can use emscripten_force_exit, if you want to force a true shutdown)';
 #endif // EXIT_RUNTIME
 #if MODULARIZE
     readyPromiseReject(msg);

src/preamble.js

@@ -407,9 +407,6 @@ function exitRuntime() {
 #if STACK_OVERFLOW_CHECK
   checkStackCookie();
 #endif
-#if USE_PTHREADS
-  if (ENVIRONMENT_IS_PTHREAD) return; // PThreads reuse the runtime from the main thread.
-#endif
 #if !STANDALONE_WASM
   ___funcs_on_exit(); // Native atexit() functions
 #endif

src/worker.js

@@ -274,7 +274,7 @@ self.onmessage = (e) => {
           }
 #if ASSERTIONS
         } else {
-          // else e == 'unwind', and we should fall through here and keep the pthread alive for asynchronous events.
+          // else ex == 'unwind', and we should fall through here and keep the pthread alive for asynchronous events.
           err('Pthread 0x' + Module['_pthread_self']().toString(16) + ' completed its main entry point with an `unwind`, keeping the worker alive for asynchronous operation.');
 #endif
         }