初识Clang

参照官网http://clang.llvm.org/get_started.html，依赖的东西还挺多，编译Clang挺慢的，耐心等待。

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On Unix-like Systems

If you would like to check out and build Clang, the current procedure is as follows:

1. Get the required tools.
   • See Getting Started with the LLVM System - Requirements.
   • Note also that Python is needed for running the test suite. Get it at: http://www.python.org/download
2. Checkout LLVM:
   • Change directory to where you want the llvm directory placed.
   • svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
3. Checkout Clang:
   • cd llvm/tools
   • svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
   • cd ../..
4. Checkout extra Clang Tools: (optional)
   • cd llvm/tools/clang/tools
   • svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk extra
   • cd ../../../..
5. Checkout Compiler-RT:
   • cd llvm/projects
   • svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt
   • cd ../..
6. Build LLVM and Clang:
   • mkdir build (for building without polluting the source dir)
   • cd build
   • ../llvm/configure
   • make
   • This builds both LLVM and Clang for debug mode.
   • Note: For subsequent Clang development, you can just do make at the clang directory level.
   • It is also possible to use CMake instead of the makefiles. With CMake it is possible to generate project files for several IDEs: Xcode, Eclipse CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.
7. If you intend to use Clang's C++ support, you may need to tell it how to find your C++ standard library headers. In general, Clang will detect the best version of libstdc++ headers available and use them - it will look both for system installations of libstdc++ as well as installations adjacent to Clang itself. If your configuration fits neither of these scenarios, you can use the --with-gcc-toolchain configure option to tell Clang where the gcc containing the desired libstdc++ is installed.
8. Try it out (assuming you add llvm/Debug+Asserts/bin to your path):
   • clang --help
   • clang file.c -fsyntax-only (check for correctness)
   • clang file.c -S -emit-llvm -o - (print out unoptimized llvm code)
   • clang file.c -S -emit-llvm -o - -O3
   • clang file.c -S -O3 -o - (output native machine code)

Note that the C front-end uses LLVM, but does not depend on llvm-gcc. If you encounter problems with building Clang, make sure you have the latest SVN version of LLVM. LLVM contains support libraries for Clang that will be updated as well as development on Clang progresses.

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