CI: Another attempt at fixing gcov OOM in CI

.github/workflows/reusable-test.yml

@@ -107,7 +107,7 @@ jobs:
       - name: Combine code coverage data
         if: ${{ inputs.dev-gcov }}
         run: |
-          make coverage-combine FASTCOV_JOBS=2
+          make coverage-combine
           mv obj_coverage/verilator.info obj_coverage/verilator-${{ inputs.suite }}.info
           ls -lsha obj_coverage
 

Makefile.in

@@ -712,7 +712,8 @@ override undefine COVERAGE_BASE # Use the above variabels instead
 FASTCOV := nodist/fastcov.py
 FASTCOV_JOBS ?= $(shell nproc)
 FASTCOV_OPT := -j $(FASTCOV_JOBS)
-FASTCOV_OPT += --gcov $(GCOV)
+# gcov does not free memory between files, so run it in batches via a wrapper
+FASTCOV_OPT += --gcov nodist/gcov_batch
 FASTCOV_OPT += --lcov
 FASTCOV_OPT += --process-gcno
 FASTCOV_OPT += --branch-coverage
@@ -786,7 +787,7 @@ $(COVERAGE_DIR)/verilator.info: $(GCNO_FILES) $(GCDA_FILES)
 	@echo "# fastcov: combining all .gcda files into lcov .info"
 	@echo "####################################################################"
 	@mkdir -p $(COVERAGE_DIR)
-	/usr/bin/time -f "That took %E" \
+	GCOV=$(GCOV) /usr/bin/time -f "That took %E" \
 	$(FASTCOV) $(FASTCOV_OPT) --output $@
 
 # Filter combined .info file for patch coverage

nodist/gcov_batch

@@ -0,0 +1,36 @@
+#!/bin/bash
+# DESCRIPTION: Verilator: gcov wrapper for fastcov, bounding gcov memory usage
+#
+# Usage: GCOV=<gcov> nodist/gcov_batch [gcov options] <files>
+#
+# fastcov passes all coverage files of a worker to a single gcov process, but
+# gcov does not free memory between input files, which can exhaust memory with
+# many files. This wrapper runs the gcov in $GCOV on batches of at most 16
+# files at a time instead. The output is the same as if all files were passed
+# to a single gcov.
+#
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+gcov="${GCOV:-gcov}"
+batch=16
+
+opts=()
+files=()
+for arg in "$@"; do
+  case "$arg" in
+    -*) opts+=("$arg") ;;
+    *) files+=("$arg") ;;
+  esac
+done
+
+# No files, e.g.: 'gcov -v'
+if [ ${#files[@]} -eq 0 ]; then
+  exec "$gcov" "${opts[@]}"
+fi
+
+status=0
+for ((i = 0; i < ${#files[@]}; i += batch)); do
+  "$gcov" "${opts[@]}" "${files[@]:i:batch}" || status=$?
+done
+exit $status