Only call __lsan_do_leak_check() for pthread builds

Non-pthreads builds can safely use atexit().

Author: kleisauke

emcc.py

@@ -2143,7 +2143,7 @@ def check_memory_setting(setting):
     if settings.LINKABLE:
       exit_with_error('ASan does not support dynamic linking')
 
-  if sanitize and settings.EXIT_RUNTIME:
+  if sanitize and settings.USE_PTHREADS and settings.EXIT_RUNTIME:
     settings.EXPORTED_FUNCTIONS += ['___lsan_do_leak_check']
 
   if sanitize and settings.GENERATE_SOURCE_MAP:

src/preamble.js

@@ -435,10 +435,10 @@ function exitRuntime() {
 #endif
 #if USE_PTHREADS
   PThread.terminateAllThreads();
-#endif
 #if EXIT_RUNTIME && (USE_LSAN || USE_ASAN)
   // Leak check should be run after all threads have been terminated.
   ___lsan_do_leak_check();
+#endif
 #endif
   runtimeExited = true;
 }

system/lib/compiler-rt/lib/sanitizer_common/sanitizer_flags.inc

@@ -71,7 +71,12 @@ COMMON_FLAG(bool, strip_env, 1,
             "avoid passing it to children. Default is true.")
 COMMON_FLAG(bool, detect_leaks, !SANITIZER_MAC, "Enable memory leak detection.")
 COMMON_FLAG(
-    bool, leak_check_at_exit, !SANITIZER_EMSCRIPTEN,
+    bool, leak_check_at_exit,
+#ifdef __EMSCRIPTEN_PTHREADS__
+    false,
+#else
+    true,
+#endif
     "Invoke leak checking in an atexit handler. Has no effect if "
     "detect_leaks=false, or if __lsan_do_leak_check() is called before the "
     "handler has a chance to run.")