Most of the security and penetration tools report if the ARC is not enabled.
fobjc-arc flag is not Found
As far as I know we can't do this in xamarin because we don't have build settings here.
This flag can be set in build settings only.
Even if we could , it won't work because xamarin uses C# and MRC to manage memory by itself.
Can anybody explain me how it can be done or not done or my understanding is wrong
Edit:
We can turn on ARC to a full project by build settings
CLANG_ENABLE_OBJC_ARC=YES
But there is no way to do this in xam studio ... setting the value in mtouch also throws error
Add the following to the Additional mtouch arguments text field within the Xamarin.iOS project properties window:
-gcc_flags "-fobjc-arc"
来源：https://stackoverflow.com/questions/43724067/enabling-in-arc-in-xamarin