Question

In the cocoa fundamentals documentary, it mentions about the different compilers. The gcc, LLVM-GCC and Clang. Does anyone specifically know what they do and when to use them?

Answer 1

They all do the same thing, produce executable object code that can be linked together to build a program (or shared library). They just do it in different ways.

1. gcc is a venerable old compiler of yore that is getting a bit long in the tooth, but is still the primary workhorse of virtually the entire open source world. It is also the most portable compiler in existence.
2. LLVM-GCC is a component of the LLVM project that uses the gcc parser front end with the LLVM code-generation backend.
3. Clang is an LLVM-specific front end that uses the LLVM back end. It is essentially a clean-room compiler that promises faster compiles producing more efficient code than gcc, all from a much smaller and cleaner code base (thanks @dreamlax).

Much more information on this is available on the LLVM site.