objc_retain behaves oddly on physical iOS devices, in certain build configurations (release mode plus other flags), when ARC is enabled. Anything from argument reordering (stack corruption) to outright crashes. My hypothesis is that calling this function explicitly under ARC might be undefined behavior that release builds can exploit for optimizations.

A more roundabout way of incrementing the ref count, that is more explicitly supported by the compiler, is to use bridge casts. These convert between ARC pointers and ordinary pointers, optionally altering the ref count.

id foo;
objc_retain(foo);
// Becomes
(__bridge id)(__bridge_retained void*)(foo);

This expression converts foo to a void* while incrementing its ref count, then converts it back to an id without changing its ref count.

Note that we're still using objc_retainBlock throughout the bindings, because it works slightly differently, and can't simply be swapped for a bridge cast (if objc_retainBlock is passed a stack allocated block, it converts it to a heap allocated block).

Unrelated change: Deleted objective_c_bindings_generated.dart.m, which is an old unused file.