Building an XRay instrumented clang binary

sample.sh

set -x

# Step 1: Build a clang using the system compiler that can build with XRay instrumentation.
mkdir llvm-build
cd llvm-build
cmake -GNinja \
  -DLLVM_ENABLE_PROJECTS="clang:compiler-rt" \
  -DCMAKE_BUILD_TYPE=Release ../llvm-project/llvm
ninja clang # Probably get a beverage and/or watch some videos
  
# Step 2: Build clang again, this time with the just-built clang with XRay support
cd ../
mkdir llvm-instrumented-build
cd llvm-instrumented-build
cmake -GNinja \
  -DLLVM_ENABLE_PROJECTS="clang" \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_CXX_COMPILER=../llvm-build/bin/clang++ \
  -DCMAKE_C_COMPILER=../llvm-build/bin/clang \
  -DCMAKE_CXX_FLAGS="-fxray-instrument" \
  -DCMAKE_CXX_FLAGS_RELEASE="-fxray-instrument" \
  ../llvm-project
ninja clang  # Probably get a beverage and/or watch some videos

# Step 3: Use the newly built clang with XRay enabled
XRAY_OPTIONS="patch_premain=true xray_mode=basic verbosity=1" ./bin/clang++ -o hello hello.cc -O3

# Step 4: You should now see a couple of XRay log files... profit?