[Tarantool-patches] [PATCH 1/2 v2] cmake: add code coverage support

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

From: Sergey Bronnikov <sergeyb@tarantool.org>

The patch adds building code coverage report using gcovr [1] and gcov.
gcovr is a better version of lcov, see [2]. There were two new CMake
targets added: LuaJIT-coverage proccess *.gcno and *.gcda files with
gcov, builds a detailed HTML report and prints a summary, target
coverage executes LuaJIT-tests and then runs LuaJIT-coverage. Target
LuaJIT-coverage is useful for building code coverage report for a custom
set of regression tests.

```
$ cmake -S . -B build -DENABLE_COVERAGE=ON
$ cmake --build build --parallel --target coverage

<snipped>

lines: 84.1% (26056 out of 30997)
functions: 88.8% (2055 out of 2314)
branches: 71.5% (14801 out of 20703)
```

1. https://gcovr.com/
2. https://gcovr.com/en/stable/faq.html#what-is-the-difference-between-lcov-and-gcovr
---
 CMakeLists.txt                        |  9 ++++++
 cmake/CodeCoverage.cmake              | 45 +++++++++++++++++++++++++++
 test/CMakeLists.txt                   |  7 +++++
 test/tarantool-c-tests/CMakeLists.txt |  6 +++-
 4 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 cmake/CodeCoverage.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6ef24bba..fe6582fa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -116,6 +116,15 @@ if(LUAJIT_ENABLE_WARNINGS)
   )
 endif()
 
+set(LUAJIT_ENABLE_COVERAGE_DEFAULT OFF)
+option(LUAJIT_ENABLE_COVERAGE
+       "Enable integration with gcovr, a code coverage program"
+       ${LUAJIT_ENABLE_COVERAGE_DEFAULT})
+if (LUAJIT_ENABLE_COVERAGE)
+  AppendFlags(CMAKE_C_FLAGS --coverage)
+  include(CodeCoverage)
+endif(LUAJIT_ENABLE_COVERAGE)
+
 # Auxiliary flags for main targets (libraries, binaries).
 AppendFlags(TARGET_C_FLAGS
   -D_FILE_OFFSET_BITS=64
diff --git a/cmake/CodeCoverage.cmake b/cmake/CodeCoverage.cmake
new file mode 100644
index 00000000..2be7d129
--- /dev/null
+++ b/cmake/CodeCoverage.cmake
@@ -0,0 +1,45 @@
+find_program(GCOVR gcovr)
+find_program(GCOV gcov)
+
+set(COVERAGE_DIR "${PROJECT_BINARY_DIR}/coverage")
+set(COVERAGE_HTML_REPORT "${COVERAGE_DIR}/luajit.html")
+set(COVERAGE_XML_REPORT "${COVERAGE_DIR}/luajit.xml")
+
+if(NOT GCOVR OR NOT GCOV)
+  add_custom_target(${PROJECT_NAME}-coverage
+    COMMAND ${CMAKE_COMMAND} -E cmake_echo_color --red "LuaJIT-coverage is a dummy target"
+  )
+  message(WARNING "Either `gcovr' or `gcov` not found, \
+so ${PROJECT_NAME}-coverage target is dummy")
+  return()
+endif()
+
+file(MAKE_DIRECTORY ${COVERAGE_DIR})
+add_custom_target(${PROJECT_NAME}-coverage)
+add_custom_command(TARGET ${PROJECT_NAME}-coverage
+  COMMENT "Building coverage report"
+  COMMAND
+    ${GCOVR}
+      # See https://gcovr.com/en/stable/guide/configuration.html
+      --root ${PROJECT_SOURCE_DIR}
+      --object-directory ${PROJECT_BINARY_DIR}
+      --filter ${PROJECT_SOURCE_DIR}/src
+      # Exclude DynASM files, that contain a low-level VM code for CPUs.
+      --exclude ".*\.dasc"
+      # Exclude buildvm source code, it's the project's infrastructure.
+      --exclude ".*/host/"
+      --print-summary
+      --output ${COVERAGE_HTML_REPORT}
+      --cobertura ${COVERAGE_XML_REPORT}
+      --html
+      --html-title "Tarantool LuaJIT Code Coverage Report"
+      --html-details
+      --sort-percentage
+      --branches
+      --decisions
+      -j ${CMAKE_BUILD_PARALLEL_LEVEL}
+  WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+)
+
+message(STATUS "Code coverage HTML report: ${COVERAGE_HTML_REPORT}")
+message(STATUS "Code coverage XML report: ${COVERAGE_XML_REPORT}")
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 47296a22..e23d6d45 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -76,4 +76,11 @@ if(LUAJIT_USE_TEST)
     ${PROJECT_NAME}-test
     ${PROJECT_NAME}-luacheck
   )
+
+  if (LUAJIT_ENABLE_COVERAGE)
+    add_custom_target(coverage DEPENDS
+      ${PROJECT_NAME}-test
+      ${PROJECT_NAME}-coverage
+    )
+  endif (LUAJIT_ENABLE_COVERAGE)
 endif()
diff --git a/test/tarantool-c-tests/CMakeLists.txt b/test/tarantool-c-tests/CMakeLists.txt
index 17255345..d74e99fc 100644
--- a/test/tarantool-c-tests/CMakeLists.txt
+++ b/test/tarantool-c-tests/CMakeLists.txt
@@ -45,7 +45,11 @@ foreach(test_source ${tests})
     OUTPUT_NAME "${exe}${C_TEST_SUFFIX}"
     RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}"
   )
-  target_link_libraries(${exe} libtest ${LUAJIT_LIBRARY})
+  set(libtest-libs libtest ${LUAJIT_LIBRARY})
+  if (LUAJIT_ENABLE_COVERAGE)
+    set(libtest-libs ${libtest-libs} --coverage)
+  endif (LUAJIT_ENABLE_COVERAGE)
+  target_link_libraries(${exe} ${libtest-libs})
   LIST(APPEND TESTS_COMPILED ${exe})
 endforeach()
 
-- 
2.34.1