Coverage report of the `check-clang-analysis` target

Community
1

I tried to create a coverage report using llvm-cov of clang executing the Static Analyzer tests via the check-clang-analysis build target.
I found that the LLVM_BUILD_INSTRUMENTED_COVERAGE=ON CMake option does this according to the documentation:
https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#collecting-coverage-reports-for-the-llvm-project

However, I’m getting this result for executing the llvm/utils/prepare-code-coverage-artifact.py script:

:: Merging raw profiles...Done!
:: Preparing html report for ['build/with-coverage/bin/clang']...warning: 10942 functions have mismatched data
warning: 10942 functions have mismatched data
Done!

Does anyone know how to set up such coverage reports?
Why do I get this 10942 functions have mismatched data warning?

Here is my reproducer:

git clone git@github.com:llvm/llvm-project.git
cd llvm-project

cmake -S llvm -B build/with-coverage -GNinja \
  -DBUILD_SHARED_LIBS=ON \
  -DCMAKE_BUILD_TYPE=Debug \
  -DCMAKE_ASM_COMPILER=clang \
  -DCMAKE_CXX_COMPILER=clang++ \
  -DCMAKE_C_COMPILER=clang \
  -DLLVM_ENABLE_ASSERTIONS=ON \
  -DLLVM_ENABLE_BINDINGS=OFF \
  -DLLVM_USE_LINKER=lld \
  -DLLVM_ENABLE_DUMP=ON \
  -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" \
  -DLLVM_TARGETS_TO_BUILD=X86 \
  -DLLVM_BUILD_INSTRUMENTED_COVERAGE=ON \
  -DLLVM_COV=$(which llvm-cov) \
  -DLLVM_PROFDATA=$(which llvm-profdata)

ninja -C build/with-coverage check-clang-analysis

llvm/utils/prepare-code-coverage-artifact.py \
  --preserve-profiles \
  -C build/with-coverage \
  $(which llvm-profdata) \
  $(which llvm-cov) \
  build/with-coverage/profiles \
  my-coverage-output-dir \
  build/with-coverage/bin/clang

/CC Some folks, as per

@ashpande @pogo59 @kpdev42 @beanz @River707 @gulfemsavrun

2

Oh, it seems like passing BUILD_SHARED_LIBS=OFF the result is much more promising. That way I have a coverage HTML, just as expected.

Should we document that you cannot have shared libs for this? I was quite confused why this doesn’t work.

However, I still get the 34 functions have mismatched data warning.
Why do I still have this?

3

The coverage report tool doesn’t traverse dynamic linkage boundaries, so you need to include all the binaries you want coverage data for in your call to the prepare-code-coverage-artifact.py script.

Your output shows you only provided clang, so it won’t generate data for any function not included in the clang binary.

4

The coverage report tool doesn’t traverse dynamic linkage boundaries, so you need to include all the binaries you want coverage data for in your call to the prepare-code-coverage-artifact.py script.

Why does it not follow dynamic linkage boundaries?