Parallelize build jobs according to CPU count

.github/workflows/coverage.yml

@@ -20,7 +20,7 @@ jobs:
           .github/scripts/install_deps.sh ubuntu-latest lcov
       - name: Generate coverage report
         run: |
-          contrib/coverage.bash ubuntu-ci
+          contrib/coverage.bash --os ubuntu-latest --jobs "$(getconf _NPROCESSORS_ONLN)"
       - name: Upload coverage report
         uses: actions/upload-artifact@v7
         with:

.github/workflows/create-release-artifacts.yml

@@ -11,9 +11,6 @@ env:
   CLICOLOR_FORCE: 1
 
   CMAKE_COLOR_DIAGNOSTICS: ON # Tells CMake-generated build systems to have colored output.
-  # Approximate number of CPU cores in GitHub's runners as of 2026-03-18:
-  # https://docs.github.com/en/actions/reference/runners/github-hosted-runners#standard-github-hosted-runners-for-public-repositories
-  CMAKE_BUILD_PARALLEL_LEVEL: 4 # `cmake --build` now implies `--parallel 4`.
   CMAKE_BUILD_TYPE: Release # `cmake -S` now implies `-DCMAKE_BUILD_TYPE=Release`.
   CMAKE_CONFIG_TYPE: Release # `cmake --build` now implies `--config Release`.
 
@@ -92,7 +89,7 @@ jobs:
           ./.github/scripts/install_deps.sh ubuntu-22.04
       - name: Build binaries
         run: |
-          make -kj WARNFLAGS="-Wall -Wextra -pedantic -static" PKG_CONFIG="pkg-config --static" Q=
+          make -k -j "$(getconf _NPROCESSORS_ONLN)" WARNFLAGS="-Wall -Wextra -pedantic -static" PKG_CONFIG="pkg-config --static" Q=
           strip rgb{asm,link,fix,gfx}
       - name: Create install script
         run: |

.github/workflows/testing.yml

@@ -11,9 +11,8 @@ env:
 
   CMAKE_COLOR_DIAGNOSTICS: ON # Tells CMake-generated build systems to have colored output.
   CMAKE_CONFIG_TYPE: Debug # `cmake --build` now implies `--config Debug`.
-  # Approximate number of CPU cores in GitHub's runners as of 2026-03-18:
+
-  # https://docs.github.com/en/actions/reference/runners/github-hosted-runners#standard-github-hosted-runners-for-public-repositories
+  CTEST_PARALLEL_LEVEL: "" # `ctest` now implies `--parallel` (default number of logical CPUs).
-  CTEST_PARALLEL_LEVEL: 0 # `ctest` now implies `--parallel 0` (number of logical CPUs).
   CTEST_NO_TESTS_ACTION: error # Make CTest fail if it cannot find any tests. (That should never happen.)
   CTEST_OUTPUT_ON_FAILURE: ON # CTest reports test program output on failure.
 
@@ -57,11 +56,11 @@ jobs:
       - name: Build using Make
         if: matrix.buildsys == 'make'
         run: |
-          make develop -kj Q= CXX=${{ matrix.cxx }}
+          make develop -k -j "$(getconf _NPROCESSORS_ONLN)" Q= CXX=${{ matrix.cxx }}
       - name: Install using Make
         if: matrix.buildsys == 'make'
         run: |
-          sudo make install -j Q=
+          sudo make install Q=
           type rgbasm rgblink rgbfix rgbgfx
           man -w 1 rgbasm rgblink rgbfix rgbgfx
       - name: Build using CMake
@@ -111,7 +110,7 @@ jobs:
       - name: Run tests using our script
         if: matrix.buildsys == 'make'
         run: |
-          CXX=${{ matrix.cxx }} test/run-tests.sh --os ${{ matrix.os }}
+          CXX=${{ matrix.cxx }} test/run-tests.sh --os ${{ matrix.os }} --jobs "$(getconf _NPROCESSORS_ONLN)"
       - name: Run tests using CTest
         if: matrix.buildsys == 'cmake'
         run: |
@@ -328,7 +327,7 @@ jobs:
           test/external/fetch-repos.sh
       - name: Run tests
         run: |
-          test/run-tests.sh --os ${{ matrix.os }}
+          test/run-tests.sh --os ${{ matrix.os }} --jobs "$(getconf _NPROCESSORS_ONLN)"
 
   cygwin:
     strategy:
@@ -365,15 +364,15 @@ jobs:
             pkg-config
       - name: Build
         run: | # Cygwin does not support `make develop` sanitizers ASan or UBSan
-          make -kj Q=
+          make -k -j "$(getconf _NPROCESSORS_ONLN)" Q=
       - name: Install
         run: |
-          make install -j Q=
+          make install Q=
           type rgbasm rgblink rgbfix rgbgfx
           man -w 1 rgbasm rgblink rgbfix rgbgfx
       - name: Run tests
         run: |
-          test/run-tests.sh --only-internal
+          test/run-tests.sh --only-internal --jobs "$(getconf _NPROCESSORS_ONLN)"
       - name: Use Windows git location in the PATH
         shell: pwsh
         run: | # Prevents the `actions/checkout` post-job cleanup from using Cygwin's git binary
@@ -400,7 +399,7 @@ jobs:
             .github/scripts/install_deps.sh freebsd
           run: | # Leak detection is not supported on FreeBSD, so disable it.
             cmake -B build --preset develop
-            cmake --build build --verbose -- -k -j 4
+            cmake --build build --verbose -- -k -j "$(getconf _NPROCESSORS_ONLN)"
             ASAN_OPTIONS=detect_leaks=0 ctest --test-dir build --schedule-random --label-exclude external
             cmake --install build --verbose
             type rgbasm rgblink rgbfix rgbgfx

Dockerfile

@@ -10,7 +10,7 @@ RUN apt-get update && \
 
 # Install dependencies and compile RGBDS
 RUN ./.github/scripts/install_deps.sh debian
-RUN make -j CXXFLAGS="-O3 -flto -DNDEBUG -static" PKG_CONFIG="pkg-config --static" Q=
+RUN make -j "$(getconf _NPROCESSORS_ONLN)" CXXFLAGS="-O3 -flto -DNDEBUG -static" PKG_CONFIG="pkg-config --static" Q=
 
 # Create the install script
 RUN make install.sh Q=

contrib/coverage.bash

@@ -1,17 +1,55 @@
 #!/usr/bin/env bash
 set -e
 
+usage() {
+	cat <<"EOF"
+Generates LCOV code coverage report for RGBDS.
+Options:
+    -h, --help     show this help message
+    -o, --open     open the HTML report in the preferred application
+    --jobs <n>     build RGBDS and external codebases with `make -j<n>`
+    --os <os>      skip tests known to fail on <os> (e.g. `macos-14`)
+EOF
+}
+
+# Parse options in pure Bash because macOS `getopt` is stuck
+# in what util-linux `getopt` calls `GETOPT_COMPATIBLE` mode
+make_args=()
+runtests_args=()
+open_report=false
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		-h|--help)
+			usage
+			exit 0
+			;;
+		-o|--open)
+			open_report=true
+			;;
+		--jobs)
+			shift
+			make_args+=("-j" "$1")
+			runtests_args+=("--jobs" "$1")
+			;;
+		--os)
+			shift
+			runtests_args+=("--os" "$1")
+			;;
+		*)
+			echo "$(basename "$0"): unknown option '$1'"
+			exit 1
+			;;
+	esac
+	shift
+done
+
 # Build RGBDS with gcov support
-make coverage -j
+make coverage "${make_args[@]}"
 
 # Run the tests
 pushd test
 external/fetch-repos.sh
-if [[ $# -eq 0 ]]; then
+./run-tests.sh "${runtests_args[@]}"
-  ./run-tests.sh
-else
-  ./run-tests.sh --os "$1"
-fi
 popd
 
 # Generate coverage logs
@@ -24,12 +62,14 @@ lcov -c --no-external -d . -o "$COVERAGE_INFO"
 lcov -r "$COVERAGE_INFO" src/asm/parser.{hpp,cpp} src/link/script.{hpp,cpp} -o "$COVERAGE_INFO"
 genhtml --dark-mode --num-spaces 4 -f -s -o coverage/ "$COVERAGE_INFO"
 
-# Check whether running from coverage.yml workflow
+if "$open_report"; then
-if [ "$1" != "ubuntu-ci" ]; then
+	# Open the report in the preferred web browser
-  # Open report in web browser
+	if [ "$(uname)" == "Darwin" ]; then
-  if [ "$(uname)" == "Darwin" ]; then
+		open coverage/index.html
-    open coverage/index.html
+	else
-  else
+		xdg-open coverage/index.html
-    xdg-open coverage/index.html
+	fi
-  fi
+else
+	# Output the path to the report
+	echo "Generated LCOV report at $PWD/coverage/index.html"
 fi

test/CMakeLists.txt

@@ -9,6 +9,15 @@ else()
 endif()
 set(TESTS_OS_NAME "${TESTS_OS_NAME}" CACHE STRING "Skip running tests known to fail on this OS.")
 
+include(ProcessorCount)
+ProcessorCount(PROCESSOR_COUNT)
+if(PROCESSOR_COUNT EQUAL 0)
+  set(PROCESSOR_COUNT 4)
+  message(STATUS "Could not determine CPU count; defaulting to ${PROCESSOR_COUNT}.")
+else()
+  message(STATUS "Counted ${PROCESSOR_COUNT} logical CPU cores.")
+endif()
+
 add_executable(randtilegen gfx/randtilegen.cpp)
 add_executable(rgbgfx_test gfx/rgbgfx_test.cpp)
 set_target_properties(randtilegen rgbgfx_test PROPERTIES
@@ -29,7 +38,7 @@ foreach(component "asm" "link" "fix" "gfx")
            COMMAND bash -- test.sh
            WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/${component}")
   set_tests_properties("rgb${component}" PROPERTIES REQUIRED_FILES "$<TARGET_FILE:rgb${component}>"
-                                                    PROCESSORS 1
+                                                    PROCESSORS 1 # These cannot be parallelized.
                                                     LABELS "internal;free")
 endforeach()
 set_tests_properties(rgbgfx PROPERTIES REQUIRED_FILES "$<TARGET_FILE:rgbgfx>;$<TARGET_FILE:randtilegen>;$<TARGET_FILE:rgbgfx_test>")
@@ -69,10 +78,10 @@ foreach(cfg_file IN LISTS ext_projects)
   endif()
 
   add_test(NAME "${project}"
-           COMMAND bash -- external/test.sh ${project}
+           COMMAND bash -- external/test.sh ${project} -j "${PROCESSOR_COUNT}"
            WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
   set_tests_properties(${project} PROPERTIES DEPENDS "rgbasm;rgblink;rgbfix;rgbgfx" # Only attempt external tests after all individual tool tests.
-                                             PROCESSORS 4
+                                             PROCESSORS "${PROCESSOR_COUNT}"
                                              LABELS "external;${freedom}"
                                              FIXTURES_REQUIRED "${freedom}-repos")
 endforeach()

test/external/fetch-repos.sh

@@ -7,10 +7,11 @@ usage() {
 	cat <<"EOF"
 Downloads source code of Game Boy project repos used as RGBDS test cases.
 Options:
-    -h, --help      show this help message
+    -h, --help         show this help message
-    --only-free     download only freely licensed codebases
+    --only-free        download only freely licensed codebases
-    --get-hash      print repos' commit hashes instead of downloading them
+    --only-nonfree     download only non-freely licensed codebases
-    --get-paths     print repos' clone paths instead of downloading them
+    --get-hash         print repos' commit hashes instead of downloading them
+    --get-paths        print repos' clone paths instead of downloading them
 EOF
 }
 

test/external/test.sh

@@ -8,13 +8,16 @@ export SOURCE_DATE_EPOCH=609165296
 
 cd "$(dirname "$0")"
 
-if [ ! -f "$1.cfg" ]; then
+NAME="$1"
-	echo >&2 'External test file '"$1"'.cfg does not exist'
+shift # Any remaining arguments get forwarded to `make`.
+
+if [ ! -f "$NAME.cfg" ]; then
+	echo >&2 'External test file '"$NAME"'.cfg does not exist'
 	exit 1
 fi
 
-# Sourcing "$1.cfg" defines `EXT_TEST_*` variables used below.
+# Sourcing "$NAME.cfg" defines `EXT_TEST_*` variables used below.
-. "$1.cfg"
+. "$NAME.cfg"
 
 if ! cd "$EXT_TEST_REPO"; then
 	echo >&2 'Please fetch test deps before running any external test'
@@ -23,7 +26,7 @@ fi
 
 RGBDS_PATH="RGBDS=../../../"
 git clean -fdx # Clean any previous build products so `make` rebuilds everything from scratch.
-make -j4 "$EXT_TEST_TARGET" $RGBDS_PATH
+make "$@" "$EXT_TEST_TARGET" $RGBDS_PATH
 
 hash="$(sha1sum -b "$EXT_TEST_FILE" | head -c 40)"
 if [ "$hash" != "$EXT_TEST_HASH" ]; then

test/run-tests.sh

@@ -16,6 +16,7 @@ Options:
     --only-internal       only run tests that build local examples
     --only-external       only run tests that build external codebases
     --only-free           skip tests that build nonfree codebases
+    --jobs <n>            build external codebases with `make -j<n>`
     --os <os>             skip tests known to fail on <os> (e.g. `macos-14`)
     --installed-rgbds     use the system installed RGBDS
                           (only compatible with external codebases)
@@ -28,6 +29,7 @@ nonfree=true
 internal=true
 external=true
 installedrgbds=false
+make_jobs=
 osname=
 while [[ $# -gt 0 ]]; do
 	case "$1" in
@@ -47,6 +49,10 @@ while [[ $# -gt 0 ]]; do
 		--installed-rgbds)
 			installedrgbds=true
 			;;
+		--jobs)
+			shift
+			make_jobs="-j$1"
+			;;
 		--os)
 			shift
 			osname="$1"
@@ -122,6 +128,6 @@ for cfg in *.cfg; do (
 
 	# Run nonfree tests only if they are opted into.
 	if ! "$EXT_TEST_IS_NONFREE" || "$nonfree"; then
-		./test.sh "$test_name"
+		./test.sh "$test_name" "$make_jobs"
 	fi
 ); done