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This attribute, called "objc_externally_retained", exposes clang's notion of pseudo-__strong variables in ARC. Pseudo-strong variables "borrow" their initializer, meaning that they don't retain/release it, instead assuming that someone else is keeping their value alive. If a function is annotated with this attribute, implicitly strong parameters of that function aren't implicitly retained/released in the function body, and are implicitly const. This is useful to expose for performance reasons, most functions don't need the extra safety of the retain/release, so programmers can opt out as needed. This attribute can also apply to declarations of local variables, with similar effect. Differential revision: https://reviews.llvm.org/D55865 llvm-svn: 350422
//===----------------------------------------------------------------------===// // C Language Family Front-end //===----------------------------------------------------------------------===// Welcome to Clang. This is a compiler front-end for the C family of languages (C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM compiler infrastructure project. Unlike many other compiler frontends, Clang is useful for a number of things beyond just compiling code: we intend for Clang to be host to a number of different source-level tools. One example of this is the Clang Static Analyzer. If you're interested in more (including how to build Clang) it is best to read the relevant web sites. Here are some pointers: Information on Clang: http://clang.llvm.org/ Building and using Clang: http://clang.llvm.org/get_started.html Clang Static Analyzer: http://clang-analyzer.llvm.org/ Information on the LLVM project: http://llvm.org/ If you have questions or comments about Clang, a great place to discuss them is on the Clang development mailing list: http://lists.llvm.org/mailman/listinfo/cfe-dev If you find a bug in Clang, please file it in the LLVM bug tracker: http://llvm.org/bugs/