What’s a reliable way to make an iOS app crash?

in Objective-C use C directly to cause a bad access

strcpy(0, "bla");

Note: while this works on any system I know — in a future version of the C runtime OR the compiler this might not lead to a crash anymore. see Is null pointer dereference undefined behavior in Objective-C?)

(in swift you would have to bridge to objC to do this)