Objective-C source code

Where can I find开发者_如何学C the source code for the Objective-C language? Is it open-source or is there an open-sourced implementation of it available?

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It really depends on what you mean by Objective-C, there are compilers, runtimes and libraries for it.

• http://opensource.apple.com/ Contains much of Apple's source code for OS X and iOS.
• you can also see http://clang.llvm.org/ for a compiler.
• GNUstep is an open source implementation of OpenStep (Cocoa).

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I think you are asking for Cocoa - and this is not open source. All you have are the header and reverse engineering tools.

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Looking around, I've found several copies of Objective-C's source code. Apple maintains it at http://opensource.apple.com/source/objc4/, which is up to date as of OS X 10.9.x Mavericks at version 551.1, but I have also found several repositories GitHub that are copies of this main repository which people have made at various points in time, so they may or may not be as up to date as Apple's main repository. These include the GitHub repositories "opensource-apple/objc4" at version 532.2; "bavarious/objc4," which is up to date at version 551.1; "macmade/OBJC4-437.1-Runtime," which obviously includes just the Objective-C runtime at version 437.1; "Apple-FOSS-Mirror/objc4" at version 532.2; "aosm," which is up to date at version 551.1; "robertvojta/objc4," which is up to date at version 551.1; "j4n0/objc4-532," which is obviously at version 532.0; and "chenniaoc/objc4-551.1," which is obviously up to date at version 551.1. Personally, it seems to me that robertvojta/objc4 is the best repository from which you could possibly fork code due to the fact that it's got every single release from Apple's Open Source website so far copied over to it.

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There is no one source code. There would be as many different versions as there are compilers for the language. They would likely be written in a low-level language such as assembly or C, and be vastly complicated. For whichever compiler you are interested in, you will need to confirm that it is open-source, which I find unlikely. Even then, it may be difficult.