Fix some errors in processing of code coverage data

We were using mismatched compiler and gcov, which led to either
segfaults or errors like "GCOV_TAG_COUNTER_ARCS mismatch". Add some
cmake code that tries to find the gcov that matches the compiler.

This should hopefully fix some of the mysterious missing coverage
problems that we've been experiencing for a while.

.github/workflows/linux-build-and-test.yaml

@@ -65,8 +65,6 @@ jobs:
         sudo apt-get update
         sudo apt-get install flex bison lcov systemd-coredump gdb libipc-run-perl \
           libtest-most-perl ${{ matrix.extra_packages }}
-        # The GCC 11 gcov segfaults with the coverage info generated by clang.
-        sudo ln -sf $(which llvm-cov-14) $(which gcov)
 
     - name: Install macOS Dependencies
       if: runner.os == 'macOS'
@@ -173,12 +171,19 @@ jobs:
       if: matrix.coverage
       run: make -j $MAKE_JOBS -k -C build coverage
 
-    - name: Upload coverage report
+    - name: Send coverage report to Codecov.io app
       if: matrix.coverage
       uses: codecov/codecov-action@v3
       with:
         file: ./build/codecov/timescaledb-codecov.info
 
+    - name: Save LCOV coverage report
+      if: matrix.coverage
+      uses: actions/upload-artifact@v3
+      with:
+        name: LCOV coverage report ${{ matrix.os }} ${{ matrix.name }} ${{ matrix.pg }}
+        path: ./build/codecov/codecov-report
+
     - name: Show regression diffs
       if: always()
       id: collectlogs

CMakeLists.txt

@@ -644,6 +644,7 @@ add_custom_target(licensecheck
 if(CODECOVERAGE)
   add_subdirectory(codecov)
 endif()
+
 if(IS_DIRECTORY ${PROJECT_SOURCE_DIR}/.git)
   configure_file(${PROJECT_SOURCE_DIR}/scripts/githooks/commit_msg.py
                  ${PROJECT_SOURCE_DIR}/.git/hooks/commit-msg COPYONLY)

codecov/CMakeLists.txt

@@ -5,7 +5,7 @@
 # the --coverage option for the compiler and this is done in the top-level
 # CMakeLists.txt so that the option covers all build targets in the project.
 #
-# Given that all dependencies (lcov, genhtml) are installed, and CMake is
+# Given that all dependencies (lcov, gcov, genhtml) are installed, and CMake is
 # initialized with -DCODECOVERAGE=ON, it should be possible to generate a code
 # coverage report by running:
 #
@@ -13,16 +13,43 @@
 #
 # The report is generated in REPORT_DIR and can be viewed in a web browser.
 
+# If we use clang, prefer the LLVM gcov. The "normal" gcov segfaults with the
+# coverage info generated by clang, and the LLVM gcov with GCC-generated
+# coverage gives weird errors like GCOV_TAG_COUNTER_ARCS mismatch.
+set(GCOV_NAMES "gcov")
+if(CMAKE_C_COMPILER_ID MATCHES "Clang|AppleClang")
+  string(REGEX MATCH "^[0-9]+" CMAKE_C_COMPILER_VERSION_MAJOR
+               ${CMAKE_C_COMPILER_VERSION})
+  list(PREPEND GCOV_NAMES "llvm-cov-${CMAKE_C_COMPILER_VERSION_MAJOR}")
+endif()
+
+find_program(GCOV NAMES ${GCOV_NAMES})
+
 # Find lcov for html output
 find_program(LCOV lcov)
 
-if(LCOV)
+if(NOT GCOV)
+  message(STATUS "Install gcov to generate code coverage reports")
+elseif(NOT LCOV)
+  message(STATUS "Install lcov to generate code coverage reports")
+else()
+  message(STATUS "Using lcov ${LCOV}:")
+  execute_process(COMMAND ${LCOV} --version)
+  message(STATUS "Using gcov ${GCOV}:")
+  execute_process(COMMAND ${GCOV} --version)
+
   # Final tracefile for code coverage
   set(OUTPUT_FILE "timescaledb-codecov.info")
 
   # Directory where to generate the HTML report
   set(REPORT_DIR "codecov-report")
 
+  # We can't directly use llvm-cov as --gcov-tool, because it has to be called
+  # like "llvm-cov gcov <gcov args>" for that. Thankfully, if its $0 is gcov, it
+  # will understand that we want it to operate like gcov. Just create a symlink.
+  add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/gcov
+                     COMMAND ln -s ${GCOV} ${CMAKE_CURRENT_BINARY_DIR}/gcov)
+
   # The baseline run needs to run before tests to learn what zero coverage looks
   # like
   add_custom_command(
@@ -32,12 +59,12 @@ if(LCOV)
       ${LCOV} --capture --initial # Initial run
       --no-external # Do not include external source files
       --base-directory ${CMAKE_SOURCE_DIR} --directory ${CMAKE_BINARY_DIR}
-      --output-file ${OUTPUT_FILE}.base
-    DEPENDS timescaledb-tsl timescaledb timescaledb-loader)
+      --output-file ${OUTPUT_FILE}.base --gcov-tool
+      ${CMAKE_CURRENT_BINARY_DIR}/gcov
+    DEPENDS timescaledb-tsl timescaledb timescaledb-loader
+            ${CMAKE_CURRENT_BINARY_DIR}/gcov)
 
-  add_custom_target(
-    coverage_base DEPENDS timescaledb-tsl timescaledb timescaledb-loader
-                          ${OUTPUT_FILE}.base)
+  add_custom_target(coverage_base DEPENDS ${OUTPUT_FILE}.base)
 
   # Ensure baseline file is generated before tests
   add_dependencies(installcheck coverage_base)
@@ -46,8 +73,10 @@ if(LCOV)
   add_custom_command(
     OUTPUT ${OUTPUT_FILE}.test
     COMMENT "Generating code coverage test file"
-    COMMAND ${LCOV} --capture --no-external --base-directory ${CMAKE_SOURCE_DIR}
-            --directory ${CMAKE_BINARY_DIR} --output-file ${OUTPUT_FILE}.test
+    COMMAND
+      ${LCOV} --capture --no-external --base-directory ${CMAKE_SOURCE_DIR}
+      --directory ${CMAKE_BINARY_DIR} --output-file ${OUTPUT_FILE}.test
+      --gcov-tool ${CMAKE_CURRENT_BINARY_DIR}/gcov
     DEPENDS ${OUTPUT_FILE}.base coverage_base)
 
   # Make sure coverage_test runs after tests (installcheck) finish
@@ -59,8 +88,10 @@ if(LCOV)
   add_custom_command(
     OUTPUT ${OUTPUT_FILE}
     COMMENT "Generating final code coverage file"
-    COMMAND ${LCOV} --add-tracefile ${OUTPUT_FILE}.base --add-tracefile
-            ${OUTPUT_FILE}.test --output-file ${OUTPUT_FILE}
+    COMMAND
+      ${LCOV} --add-tracefile ${OUTPUT_FILE}.base --add-tracefile
+      ${OUTPUT_FILE}.test --output-file ${OUTPUT_FILE} --gcov-tool
+      ${CMAKE_CURRENT_BINARY_DIR}/gcov
     DEPENDS ${OUTPUT_FILE}.test coverage_test)
 
   add_custom_target(coverage_final DEPENDS ${OUTPUT_FILE})
@@ -90,14 +121,12 @@ if(LCOV)
     add_dependencies(coverage coverage_final)
 
     add_custom_command(
-      TARGET coverage
-      POST_BUILD
-      COMMENT
+      COMMAND
+        echo
         "Open file://${CMAKE_CURRENT_BINARY_DIR}/${REPORT_DIR}/index.html in a browser to view the report"
-    )
+        TARGET coverage POST_BUILD
+      COMMENT)
   else()
     message(STATUS "Install genhtml to generate code coverage reports")
   endif(GENHTML)
-else()
-  message(STATUS "Install lcov to generate code coverage reports")
-endif(LCOV)
+endif()