Under what conditions is @synthesize automatic in Objective-c?

Question

Under what conditions is @synthesize automatic in Objective-c?

Perhaps when using LLVM 3.0 and up? From reading around the net it seems like

Answer 1

From the New Features in Xcode 4.4 document:

Objective-C @properties are synthesized by default when not explicitly implemented.

So @synthesize is automatic by default starting from Xcode 4.4 with the LLVM 4.0 Compiler.