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.cs.uiuc.edu/mailman/listinfo/cfe-dev

If you find a bug in Clang, please file it in the LLVM bug tracker:
http://llvm.org/bugs/

Compiling libclang with Xcode

1. git pull the latest versions of:

• llvm ($LLVM/llvm, cloned from http://llvm.org/git/llvm.git ),
• compiler-rt ($LLVM/llvm/projects/compiler-rt, cloned from http://llvm.org/git/compiler-rt.git )
• clang ($LLVM/llvm/tools/clang, cloned from this repo or from http://llvm.org/git/clang.git )

2. Build LLVM and Clang

   cd $LLVM/build cmake -G "Unix Makefiles" ../llvm make -j 8

Notes:

• -j 8: parallel compilation with 8 jobs simultaneously (adapt it for your machine CPU)

• You need to have cmake accessible from the command line. If the cmake command is not found, download cmake for macOS from https://cmake.org/download/, and create symbolic links for cmake and cmakexbuild in /usr/local/bin

    > cd /usr/local/bin
    > sudo ln -s /Applications/CMake.app/Contents/bin/cmake .
    > sudo ln -s /Applications/CMake.app/Contents/bin/cmakexbuild . 
  

• If you get an error "'libxml/parser.h' file not found", make sure that libxml2 is installed in /usr/include. If not, or if /usr/include does not exist, run the following command:

    > xcode-select --install
  

  This will install various command-line tools for Xcode, including libxml2.

3. Create an Xcode project for llvm

   mkdir xcode-project cd $LLVM/xcode-project cmake -G Xcode ../llvm

4. Fix the Clang Xcode project

• set the base SDK to 'Latest OS X'
• add the libclang exported header files (the ones in $LLVM/llvm/tools/clang/include/clang-c) to the Clang Xcode Project (for example, put these exported header files in a new group Include in Sources -> Clang libraries -> libclang, or wherever you like best).
• in target libclang:
  • set dynamic Library install name to @rpath/$(EXECUTABLE_PATH)
  • add a Copy Files build phase for the exported headers:
    Destination: Absolute Path;
    Subpath: $(BUILT_PRODUCTS_DIR)/libclang/include/clang-c;
    Files: CXString.h, Platform.h, Index.h, BuildSystem.h, CXCompilationDatabase.h, CXErrorCode.h, Documentation.h
  • add a Run Script build phase for copying the dynamic library: cp -p ${SCRIPT_INPUT_FILE_0} ${SCRIPT_OUTPUT_FILE_0}
    Input Files: $(BUILT_PRODUCTS_DIR)/$(EXECUTABLE_PATH)
    Output Files: $(BUILT_PRODUCTS_DIR)/libclang/libclang.dylib

5. Recompile libclang from Xcode

6. You will find libclang.dylib and the associated include files in $LLVM/xcode-project/Release/lib/libclang (or in $LLVM/xcode-project/Debug/lib/libclang if you have compiled in Debug mode)

Further reading

For more generic information about compiling llvm and clang, you can read: http://www.stuartcarnie.com/2012/06/llvm-clang-hacking-part-1.html and http://clang.llvm.org/get_started.html