ci: Add lcov configuration to ignore g_return_*if_fail()/g_assert*()

While we can’t add markers to the macro implementations to cause lcov to
ignore them automatically, we can change our lcov configuration to
ignore all calls to them.

See https://github.com/linux-test-project/lcov/issues/44.

This causes all the un-takeable branches and un-reachable assertions to
be ignored by our code coverage, which bumps our statistics:
 • Lines: 74.9% → 74.8%
 • Functions: 82.3% → 82.3%
 • Branches: 53.3% → 64.2%

The rationale is that nobody should be testing programmer error
handling, as g_return_*if_fail() are used to guard against — so it’s not
reasonable to count missed branches like that in code coverage
statistics.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

.gitlab-ci.yml

@@ -24,9 +24,9 @@ fedora-x86_64:
     - meson ${MESON_COMMON_OPTIONS} --werror -Dsystemtap=true -Ddtrace=true -Dfam=true _build
     - ninja -C _build
     - mkdir -p _coverage
-    - lcov --rc lcov_branch_coverage=1 --directory _build --capture --initial --output-file "_coverage/${CI_JOB_NAME}-baseline.lcov"
+    - lcov --config-file .gitlab-ci/lcovrc --directory _build --capture --initial --output-file "_coverage/${CI_JOB_NAME}-baseline.lcov"
     - meson test -C _build --timeout-multiplier ${MESON_TEST_TIMEOUT_MULTIPLIER}
-    - lcov --rc lcov_branch_coverage=1 --directory _build --capture --output-file "_coverage/${CI_JOB_NAME}.lcov"
+    - lcov --config-file .gitlab-ci/lcovrc --directory _build --capture --output-file "_coverage/${CI_JOB_NAME}.lcov"
   artifacts:
     name: "glib-${CI_JOB_NAME}-${CI_COMMIT_REF_NAME}"
     when: always

.gitlab-ci/coverage-docker.sh

@@ -7,14 +7,14 @@ python3 ./.gitlab-ci/fixup-cov-paths.py _coverage/*.lcov
 
 for path in _coverage/*.lcov; do
     # Remove coverage from generated code in the build directory
-    lcov --rc lcov_branch_coverage=1 -r "${path}" '*/_build/*' -o "$(pwd)/${path}"
+    lcov --config-file .gitlab-ci/lcovrc -r "${path}" '*/_build/*' -o "$(pwd)/${path}"
     # Remove any coverage from system files
-    lcov --rc lcov_branch_coverage=1 -e "${path}" "$(pwd)/*" -o "$(pwd)/${path}"
+    lcov --config-file .gitlab-ci/lcovrc -e "${path}" "$(pwd)/*" -o "$(pwd)/${path}"
 done
 
 genhtml \
     --ignore-errors=source \
-    --rc lcov_branch_coverage=1 \
+    --config-file .gitlab-ci/lcovrc \
     _coverage/*.lcov \
     -o _coverage/coverage
 

.gitlab-ci/lcovrc

@@ -0,0 +1,13 @@
+# lcov and genhtml configuration
+# See http://ltp.sourceforge.net/coverage/lcov/lcovrc.5.php
+
+# Always enable branch coverage
+lcov_branch_coverage = 1
+
+# Exclude precondition assertions, as we can never reasonably get full branch
+# coverage of them, as they should never normally fail.
+# See https://github.com/linux-test-project/lcov/issues/44
+lcov_excl_br_line = LCOV_EXCL_BR_LINE|g_return_if_fail|g_return_val_if_fail|g_assert|g_assert_
+
+# Similarly for unreachable assertions.
+lcov_excl_line = LCOV_EXCL_LINE|g_return_if_reached|g_return_val_if_reached|g_assert_not_reached

.gitlab-ci/test-msys2.sh

@@ -44,7 +44,7 @@ ninja
 
 "${LCOV}" \
     --quiet \
-    --rc lcov_branch_coverage=1 \
+    --config-file .gitlab-ci/lcovrc \
     --directory "${DIR}/_build" \
     --capture \
     --initial \
@@ -55,7 +55,7 @@ meson test --timeout-multiplier ${MESON_TEST_TIMEOUT_MULTIPLIER} || true
 
 "${LCOV}" \
     --quiet \
-    --rc lcov_branch_coverage=1 \
+    --config-file .gitlab-ci/lcovrc \
     --directory "${DIR}/_build" \
     --capture \
     --output-file "${DIR}/_coverage/${CI_JOB_NAME}.lcov"