Change Functions to be more robust if App is deleted out from under them.

If App is deleted, invalidate the internal pointers (e.g. FunctionsInternal)
rather than the outer pointers (Functions), so that later code can still
delete the outer pointer.

PiperOrigin-RevId: 238808270

Author: chkuang-g

functions/src/common/functions.cc

@@ -115,13 +115,18 @@ Functions::Functions(::firebase::App* app, const char *region) {
             static_cast<int>(reinterpret_cast<intptr_t>(functions)),
             static_cast<int>(reinterpret_cast<intptr_t>(
                 functions->app())));
-        delete functions;
+        functions->DeleteInternal();
       });
   }
 }
 
-Functions::~Functions() {
+Functions::~Functions() { DeleteInternal(); }
+
+void Functions::DeleteInternal() {
   MutexLock lock(g_functions_lock);
+
+  if (!internal_) return;
+
   CleanupNotifier* app_notifier = CleanupNotifier::FindByOwner(app());
   assert(app_notifier);
   app_notifier->UnregisterObject(this);
@@ -140,13 +145,17 @@ Functions::~Functions() {
   }
 }
 
-::firebase::App* Functions::app() { return internal_->app(); }
+::firebase::App* Functions::app() {
+  return internal_ ? internal_->app() : nullptr;
+}
 
 HttpsCallableReference Functions::GetHttpsCallable(const char* name) const {
+  if (!internal_) return HttpsCallableReference();
   return HttpsCallableReference(internal_->GetHttpsCallable(name));
 }
 
 void Functions::UseFunctionsEmulator(const char* origin) {
+  if (!internal_) return;
   internal_->UseFunctionsEmulator(origin);
 }
 

functions/src/include/firebase/functions.h

@@ -99,6 +99,9 @@ class Functions {
   Functions(const Functions& src);
   Functions& operator=(const Functions& src);
 
+  // Delete the internal_ data.
+  void DeleteInternal();
+
   internal::FunctionsInternal* internal_;
   /// @endcond
 };