Cython line tracing for coverage analysis

[ajfriend]

I'm trying to figure out how to turn on code coverage for Cython files in my project here: https://github.com/uber/h3-py

Based on these notes:

• https://cython.readthedocs.io/en/latest/src/tutorial/profiling_tutorial.html#enabling-line-tracing
• https://cython.readthedocs.io/en/latest/src/tutorial/profiling_tutorial.html#enabling-coverage-analysis

it sounds like the first step is to define CYTHON_TRACE=1.

With scikit-build, I'm not sure if I should be doing this in the setup.py file, the cmake files, or elsewhere.

Has anyone else gotten this to work, and could offer some pointers? Thanks!

[jcfr]

I suggest you try the following:

python setup.py build -- -DCYTHON_FLAGS:STRING="--directive profile=True" -DCMAKE_CXX_FLAGS:STRING=-DCYTHON_TRACE=1

or

CXXFLAGS=-DCYTHON_TRACE=1 python setup.py build -- -DCYTHON_FLAGS:STRING="--directive profile=True"

• CYTHON_FLAGS is a cache variable allowing to pass additional options to cython executable:
    * It is briefly documented at https://scikit-build.readthedocs.io/en/latest/cmake-modules/Cython.html#command:add_cython_target
    * Implementation is in the UseCython module (see here and here)

• Cython compiler directives are documented at https://cython.readthedocs.io/en/latest/src/userguide/source_files_and_compilation.html#compiler-directives and can be passed to cython executable using the -X or --directive argument.

• To define CYTHON_TRACE, there are few possible approaches:

  • Setting CXXFLAGS is a convenient way to pass compilation flags to the CMake project internally built by scikit-build. See https://cmake.org/cmake/help/latest/envvar/CXXFLAGS.html
  • Passing CMAKE_CXX_FLAGS variable. See https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_FLAGS.html#variable:CMAKE_%3CLANG%3E_FLAGS

[cmpute]

I would also suggest that add these lines to your CMakeLists.txt:

if(DEFINED ENV{BUILD_COV})
  add_compile_definitions(CYTHON_TRACE=1)
  set(CYTHON_FLAGS "-X linetrace=True")
endif()

This way you can enable linetrace by set environment variable BUILD_COV