This document describes how to build a debug version of LLVM for use with LLDB, and how to make LLDB use it. It assumes that you are using the Xcode 3 series (I used 3.2.4) to build LLDB. It also assumes that your shell is /bin/bash, and that you are currently at a shell prompt in a checked-out LLDB repository. 1. Check out LLVM and Clang from their repositories. To determine the revision to use, consult scripts/build-llvm.pl (this is done in the first command line below). !!! WARNING Do not use the name "llvm" for your checkout, for reasons described in part 3 below. $ export CLANG_REVISION=`cat scripts/build-llvm.pl | grep ^our.*llvm_revision | cut -d \' -f 2,2` $ svn co -r $CLANG_REVISION http://llvm.org/svn/llvm-project/llvm/trunk llvm.checkout $ svn co -r $CLANG_REVISION http://llvm.org/svn/llvm-project/cfe/trunk llvm.checkout/tools/clang 2. Configure LLVM/Clang with the proper options and compilers. I use: $ cd llvm.checkout $ CC="cc -g -O0" CXX="c++ -g -O0" ./configure --disable-optimized --enable-assertions --enable-targets=x86_64,arm $ CC="cc -g -O0" CXX="c++ -g -O0" make -j 2 $ cd .. 3. Create a link to the built LLVM. !!! WARNING: Do not rename the directory! The LLVM builder script that runs as part of the Xcode build keys off the fact that llvm/ is a symlink to recognize that we are building with a custom debug build. $ ln -sf llvm.checkout llvm 4. Make sure that your Xcode project is set up correctly. Open lldb.xcodeproj and do the following: Under "Targets" in the Groups & Files navigator, double-click lldb-tool. In the resulting window, select "Debug" from the "Configuration:" drop-down. Then, make sure that the setting "Build Active Architecture Only" is enabled. Close the window. Under "Targets" in the Groups & Files navigator, double-click LLDB. In the resulting window, select "Debug" from the "Configuration:" drop-down. Then, make sure that the setting "Build Active Architecture Only" is enabled. Close the window. 5. Ensure that Xcode is building the lldb-tool target in Debug configuration for your architecture (typically x86_64). You can usually pick these options from the Overview drop-down at the top left of the Xcode window. 6. Build lldb.xcodeproj.