Prevent runtime exit while main is running

See #17376 for the original report inspiration for the modified test.

Author: sbc100

emcc.py

@@ -2492,6 +2492,10 @@ def check_memory_setting(setting):
     # MINIMAL_RUNTIME only needs callRuntimeCallbacks in certain cases, but the normal runtime
     # always does.
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$callRuntimeCallbacks']
+    if settings.EXIT_RUNTIME:
+      # Use by callMain
+      # TODO(sbc): have callMain use callUserCallback instead.
+      settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$runtimeKeepalivePush', '$runtimeKeepalivePop']
 
   if settings.EXIT_RUNTIME and not settings.STANDALONE_WASM:
     # Internal function implemented in musl that calls any functions registered

src/postamble.js

@@ -167,7 +167,9 @@ function callMain(args) {
     // that if we get here main returned zero.
     var ret = 0;
 #else
+    {{{ runtimeKeepalivePush() }}}
     var ret = entryFunction(argc, argv);
+    {{{ runtimeKeepalivePop() }}}
 #endif // STANDALONE_WASM
 
 #if BENCHMARK

tests/browser/test_glfw3.c

@@ -41,8 +41,14 @@ assert(glfwSet##Function(Value) == Value); /* The previously set callback */
 assert(glfwSet##Function(Window, Value) == NULL);  /* Default value (no callback was set) */ \
 assert(glfwSet##Function(Window, Value) == Value); /* The previously set callback */
 
-int main()
-{
+static int exited = 0;
+
+__attribute__((destructor))
+void onExit() {
+    exited = 1;
+}
+
+int main() {
     GLFWwindow *window;
     char *userptr = "userptr";
 
@@ -121,9 +127,11 @@ int main()
         glfwSetWindowSize(window, 1, 1);
         glfwGetWindowSize(window, &w, &h);
         assert(w == 1 && h == 1);
+        assert(exited == 0);
 
         glfwSetWindowSize(window, 640, 480);
         glfwGetFramebufferSize(window, &w, &h);
+        assert(exited == 0);
 
         // XXX: not implemented
         // glfwIconifyWindow(window);
@@ -210,9 +218,6 @@ int main()
 #endif
 
     glfwTerminate();
-
-#ifdef REPORT_RESULT
-    REPORT_RESULT(1);
-#endif
+    printf("done\n");
     return 0;
 }

tests/test_browser.py

@@ -2881,7 +2881,7 @@ def in_html(expected):
   def test_glfw3(self, args):
     for opts in [[], ['-sLEGACY_GL_EMULATION'], ['-Os', '--closure=1']]:
       print(opts)
-      self.btest(test_file('browser/test_glfw3.c'), args=['-sUSE_GLFW=3', '-lglfw', '-lGL'] + args + opts, expected='1')
+      self.btest_exit(test_file('browser/test_glfw3.c'), args=['-sUSE_GLFW=3', '-lglfw', '-lGL'] + args + opts)
 
   @requires_graphics_hardware
   def test_glfw_events(self):