Instrumented every build configuration and merged their coverage (#665)

Only default_build_coverage carried -fprofile-arcs, because the gate was the
build type and it is the only one of five whose name ends in _coverage. The
other four build and run all their tests and their coverage was discarded. That
is not redundancy thrown away: each configuration selects a different set of TX_
feature macros, so the code the other four compile is absent from the
denominator rather than uncovered in it.

TX_COVERAGE instruments a build regardless of its name, defaulting to OFF so a
single configuration built by hand behaves as before. coverage.sh gains a
--merge mode that unions the per-configuration JSON tracefiles, and
cmake_bootstrap.sh runs it after the test loop so a local run produces the same
merged report CI reads. The template sets TX_COVERAGE for build and test, and
coverage_name moves to the merged report.

Measured on the ThreadX suite, all 480 tests passing:

  default_build_coverage           3827 valid   3827 covered
  disable_notify_callbacks_build   3767         3766
  stack_checking_build             3857         3856
  stack_checking_rand_fill_build   3862         3861
  trace_build                      4123         4108
  merged                           4503         4487

The denominator grows by 676 lines, 17.7%, and the figure moves from 99.97% to
99.64%. The second one is honest, and the drop is the point rather than a
regression: the denominator now includes code the old report never counted. The
union also contains a file the old report did not contain at all --
tx_thread_stack_error_handler.c compiles only under TX_ENABLE_STACK_CHECKING, so
it was not listed at 0%, it was simply absent. 177 files becomes 178.

Coverage collection moved out of test() and now runs after the test loop, one
configuration at a time. gcov writes its intermediate gcov files into the
directory gcovr is rooted at, and coverage.sh roots every configuration at the
repository root so filenames come out repo-relative. Five concurrent gcovr
processes therefore share one scratch directory and delete each other's output:
the first full run of this change passed all 480 tests and produced no report
for three of the five configurations. Measured both ways -- two gcovr rooted at
the repository root fail concurrently and succeed in sequence. CI would not
have caught it, because test_tx.sh sets CTEST_PARALLEL_LEVEL=1 and takes the
serial branch.

Per-configuration output moved under coverage_report/per_configuration/ and is
excluded from the Pages artifact. The deploy job merges the ThreadX and SMP
artifacts into one tree and every configuration directory has the same name in
both, so left at the top level one suite's would overwrite the other's on the
published site.

On the SMP suite, an earlier run of this change saw trace_build fail
threadx_smp_time_slice_test and then hang, which raised the question of whether
-fprofile-arcs perturbs a timing-sensitive test. It does not. Sixteen runs
settle it, and the decisive one is that threadx_smp_time_slice_test failed
ERROR #31 -- twice in a row under --repeat until-pass:2 -- on an uninstrumented
build, in the exact shape CI runs, while three instrumented runs of that shape
passed 5 of 5. In the CI shape, CTEST_PARALLEL_LEVEL=1 run.sh test all:

  TX_COVERAGE=OFF   3 runs   2 green, one ERROR #31        310 s
  TX_COVERAGE=ON    3 runs   3 green, 5/5 each             325-329 s

So the test is a pre-existing flake on dev and instrumenting all five costs
about 5% of the suite's wall clock. Separately, and also in both instrumented
and uninstrumented builds, run.sh's parallel branch -- what a developer gets
typing run.sh test all with no CTEST_PARALLEL_LEVEL -- hangs under its own load,
four times in twelve runs. Several SMP tests create 1024 ThreadX threads by
construction and the Linux port backs each with a pthread, so five
configurations at once put on the order of 5000 threads on the machine. CI sets
CTEST_PARALLEL_LEVEL=1 and does not take that branch.

Assisted-by: Claude Opus 5 <noreply@anthropic.com>

test/tx/cmake/CMakeLists.txt

@@ -62,7 +62,21 @@ add_subdirectory(regression)
 add_subdirectory(samples)
 
 # Coverage
-if(CMAKE_BUILD_TYPE MATCHES ".*_coverage")
+#
+# The gate here used to be the build type alone, and only one of the five
+# configurations -- default_build_coverage -- has a name matching "*_coverage".
+# So four configurations built and ran every test and their coverage was thrown
+# away. That is not redundancy discarded: each configuration selects a different
+# set of TX_ feature macros, so the code the other four compile is *absent from
+# the denominator* rather than reported as uncovered. A figure taken from one of
+# them is the executable-line count of one configuration, not of the kernel.
+#
+# TX_COVERAGE instruments a build regardless of its name. It defaults to OFF and
+# the build-type match is kept, so configuring a single configuration by hand
+# behaves exactly as it did before; the regression run turns it on for all five
+# and merges the results.
+option(TX_COVERAGE "Instrument this build for coverage regardless of build type" OFF)
+if(TX_COVERAGE OR CMAKE_BUILD_TYPE MATCHES ".*_coverage")
   if(NOT MSVC)
     target_compile_options(threadx PRIVATE -fprofile-arcs -ftest-coverage)
     target_link_options(threadx PRIVATE -fprofile-arcs -ftest-coverage)

test/tx/cmake/coverage.sh

@@ -14,7 +14,6 @@
 set -e
 
 cd $(dirname $0)
-mkdir -p coverage_report/$1
 
 # gcov reads a data format tied to the compiler that produced it, so gcov has to match
 # the gcc that built the objects. Since cmake/linux.cmake began honouring CC, taking
@@ -41,6 +40,57 @@ if ! command -v "$GCOV" >/dev/null 2>&1; then
     exit 1
 fi
 
+# The repository root, needed by every mode below. It has to be absolute: see the
+# note on the per-configuration paths further down.
+repo_root=$(cd ../../.. && pwd)
+filter=$repo_root/common/src
+
+# --merge unions the per-configuration reports into the one number that means
+# something. Each configuration writes an intermediate JSON beside its XML, and
+# this pass adds them all together.
+#
+# Reporting five separate percentages instead would invite a reader to average
+# them, and an average is not a coverage figure -- a line covered only by
+# trace_build is covered, and only the union says so.
+#
+# Do not be alarmed when the merged percentage is lower than the single
+# configuration this used to report. That is the point: the denominator now
+# includes code the old report never counted at all, because it was compiled out
+# of the only instrumented build.
+if [ "$1" = "--merge" ]; then
+    shopt -s nullglob
+    tracefiles=(coverage_report/per_configuration/*.json)
+    shopt -u nullglob
+    if [ ${#tracefiles[@]} -eq 0 ]; then
+        echo "coverage.sh --merge: no JSON in coverage_report/per_configuration/." >&2
+        echo "Run the suites with TX_COVERAGE=ON first." >&2
+        exit 1
+    fi
+
+    add_args=()
+    for t in "${tracefiles[@]}"; do
+        add_args+=(--add-tracefile "$t")
+    done
+
+    mkdir -p coverage_report/merged
+    gcovr -r "$repo_root" "${add_args[@]}" --xml-pretty --output coverage_report/merged.xml
+    gcovr -r "$repo_root" "${add_args[@]}" --html --html-details --output coverage_report/merged/index.html
+
+    if ! grep -q "<class " coverage_report/merged.xml; then
+        echo "coverage.sh --merge: the merged report contains no files." >&2
+        exit 1
+    fi
+
+    # Named, not just counted. coverage_report/ is not cleaned between runs, so a
+    # tracefile left by an earlier run of a different set of configurations would
+    # otherwise be merged in without anything saying so.
+    echo "coverage.sh --merge: ThreadX, ${#tracefiles[@]} configuration(s):"
+    for t in "${tracefiles[@]}"; do
+        echo "    $(basename "$t" .json)"
+    done
+    exit 0
+fi
+
 # gcovr is given three paths below, and each of them has to be absolute, for a
 # different reason.
 #
@@ -55,8 +105,8 @@ fi
 #
 # Both -r and -f must be absolute. "-r ../../.. -f common/src" produces a report
 # containing zero files and exits 0, which is the worst failure mode available
-# here: a green run carrying an empty report. Measured, not assumed.
-repo_root=$(cd ../../.. && pwd)
+# here: a green run carrying an empty report. Measured, not assumed. repo_root
+# and filter are set above, before the merge mode, because it needs them too.
 
 # This is what actually scopes the report to one build configuration, and it is
 # the positional search path -- not --object-directory, which used to be here
@@ -79,17 +129,26 @@ objdir=$PWD/build/$1/threadx/CMakeFiles/threadx.dir/common/src
 # ports are validated functionally rather than structurally, and linux/gnu is a
 # development host port that nothing ships on. Written down because a filter
 # argument on its own is not a decision the next reader can see.
-filter=$repo_root/common/src
 
-gcovr --gcov-executable "$GCOV" -r "$repo_root" -f "$filter" "$objdir" --xml-pretty --output coverage_report/$1.xml
-gcovr --gcov-executable "$GCOV" -r "$repo_root" -f "$filter" "$objdir" --html --html-details --output coverage_report/$1/index.html
+# Per-configuration output is kept in a subdirectory of its own, and the merged
+# report sits alongside it at the top. That is not tidiness: the Pages deploy
+# uploads coverage_report wholesale and merges the ThreadX and SMP artifacts
+# into one tree, and every configuration directory has the same name in both
+# suites. Left at the top level, default_build_coverage/ from one suite would
+# overwrite the other's on the published site. Nested here, the top level still
+# holds exactly the one suite directory the deploy expects.
+mkdir -p coverage_report/per_configuration/$1
+gcovr --gcov-executable "$GCOV" -r "$repo_root" -f "$filter" "$objdir" \
+      --json coverage_report/per_configuration/$1.json \
+      --xml-pretty --output coverage_report/per_configuration/$1.xml
+gcovr --gcov-executable "$GCOV" -r "$repo_root" -f "$filter" "$objdir" --html --html-details --output coverage_report/per_configuration/$1/index.html
 
 # An empty report is not an error as far as gcovr is concerned: it warns and
 # exits 0. Worse, it advertises line-rate="1.0" alongside lines-valid="0", so
 # every downstream consumer reads "no data at all" as "100% covered". A coverage
 # threshold cannot catch that, because an empty report passes any threshold. So
 # the assertion belongs here, next to the paths that would cause it.
-if ! grep -q "<class " coverage_report/$1.xml; then
+if ! grep -q "<class " coverage_report/per_configuration/$1.xml; then
     echo "coverage.sh: the report for '$1' contains no files." >&2
     echo "Expected gcda files under $objdir." >&2
     exit 1