primesearch · ixfd64 · Aug 1, 2026 · Jul 27, 2026
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -0,0 +1,142 @@
+# This file is part of mfaktc.
+# Copyright (c) 2025        NStorm (https://github.com/N-Storm)
+# Copyright (c) 2009-2011   Oliver Weihe (o.weihe@t-online.de)
+#
+# mfaktc is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# mfaktc is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with mfaktc.  If not, see <http://www.gnu.org/licenses/>.
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+name: mfaktc CI
+
+on:
+  push:
+    paths-ignore:
+      - '**/*.txt'
+      - '**/*.ini'
+      - 'COPYING'
+      - '.gitignore'
+  pull_request:
+    paths-ignore:
+      - '**/*.txt'
+      - '**/*.ini'
+      - 'COPYING'
+      - '.gitignore'
+    types:
+      - 'opened'
+      - 'reopened'
+      - 'synchronize'
+      - 'ready_for_review'
+  schedule:
+    - cron: '0 0 1 * *'
+
+jobs:
+# Begin job "Linux"
+  Linux:
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      # If set to true, all jobs within the same matrix (such as Linux or
+      # Windows builds) will be aborted at the same time if any one job fails.
+      fail-fast: false
+
+      matrix:
+        os: [ubuntu-22.04, ubuntu-24.04, ubuntu-26.04]
+        cc: [gcc, clang]
+
+    env:
+      CC: ${{ matrix.cc }}
+      CXX: ${{ matrix.cc == 'gcc' && 'g++' || 'clang++' }}
+
+    steps:
+
+      - name: Checkout repo
+        uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+          fetch-tags: true
+
+      - name: Update and install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y nvidia-cuda-toolkit
+
+      - name: Prepare sources
+        run: |
+          cuda_version=$(nvcc --version | awk '/release/ { sub(/^V/, "", $NF); print $NF }')
+          bash .github/workflows/scripts/build_helper.sh "$cuda_version"
+
+      - name: Build from sources
+        run: |
+          cd src
+          make -O -j$(nproc) DEBUG=1
+          make clean
+
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v7
+        if: always()
+        with:
+          name: mfaktc-linux64-${{ matrix.os }}-${{ matrix.cc }}
+          path: ${{ github.workspace }}
+# End job "Linux"
+
+# Begin job "Windows"
+  Windows:
+    # windows-2022 also works and produces nearly identical binaries, so let's
+    # target the image that will be supported in the longer term. windows-2025
+    # is in beta as of June 2025, but testing has shown it is reliable.
+    runs-on: windows-2022
+
+    steps:
+
+      - name: Checkout repo
+        uses: actions/checkout@v7
+        with:
+          fetch-depth: 0
+          fetch-tags: true
+
+      - name: Install CUDA Toolkit
+        uses: N-Storm/cuda-toolkit@v0.2.34
+
+      - name: Prepare sources
+        shell: bash
+        run: |
+          cuda_version=$(nvcc --version | awk '/release/ { sub(/^V/, "", $NF); print $NF }')
+          bash .github/workflows/scripts/build_helper.sh "$cuda_version"
+
+      - name: Build from sources with MSVC
+        shell: cmd
+        run: |
+          "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvars64.bat" x64 || exit /b 1
+          cd src || exit /b 1
+          copy mfaktc.ini .. || exit /b 1
+          make SHELL="cmd.exe" -j%NUMBER_OF_PROCESSORS% -f Makefile.win DEBUG=1 || exit /b 1
+          make clean -f Makefile.win || exit /b 1
+
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v7
+        if: always()
+        with:
+          name: mfaktc-win64
+          path: ${{ github.workspace }}
+# End job "Windows"
+
+  ShellCheck:
+    name: ShellCheck
+
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v7
+    - name: Script
+      run: shopt -s globstar; shellcheck -o avoid-nullary-conditions,check-set-e-suppressed,deprecate-which,quote-safe-variables,require-double-brackets -s bash **/*.sh
+      continue-on-error: true
diff --git a/.github/workflows/scripts/build_helper.sh b/.github/workflows/scripts/build_helper.sh
@@ -26,6 +26,8 @@
 # support building under GitHub Actions runner environments and compiling
 # kernels for all devices with NVCC-supported compute capabilities.
 
+set -e -o pipefail
+
 if [[ -z "$1" ]]; then
   echo "Usage: $0 <CUDA version>" >&2
   exit 1
@@ -35,7 +37,7 @@ fi
 # to GNU sort
 export GSORT='/usr/bin/sort'
 
-CUDA_VERSION_FULL="$(echo "$1" | head -n1 | grep -Eom1 -e '^[1-9]([0-9])?\.[0-9]{1,2}(\.[0-9]{1,3})?$')"
+CUDA_VERSION_FULL=$(echo "$1" | head -n1 | grep -Eom1 -e '^[1-9]([0-9])?\.[0-9]{1,2}(\.[0-9]{1,3})?$')
 declare -a CUDA_VERSION
 IFS=" " read -r -a CUDA_VERSION <<< "$(echo "$CUDA_VERSION_FULL" | tr '.' ' ')"
 if [[ -z "${CUDA_VERSION[*]}" ]]; then
@@ -54,18 +56,18 @@ printf -v CUDA_VER %d%02d "${CUDA_VER_MAJOR}" "${CUDA_VER_MINOR}";
 # CUDA supports the --list-gpu-arch flag from 11.0.0 onwards.
 # For older CUDA versions, use grep to parse the supported architectures from
 # the output of --help
-[ "$CUDA_VER" -gt 1100 ] && NVCC_OPTS='--list-gpu-arch' || NVCC_OPTS='--help'
+[[ "$CUDA_VER" -gt 1100 ]] && NVCC_OPTS='--list-gpu-arch' || NVCC_OPTS='--help'
 NVCC_REGEX='compute_[1-9][0-9]{1,2}'
 # CUDA 11.0.x is a special case. Its --help output lists compute_32 and higher,
 # but only compute capability 3.5 and later are supported.
-[ "$CUDA_VER" -eq 1100 ] && NVCC_REGEX='compute_(3[5-9]|[4-9][0-9])'
+[[ "$CUDA_VER" -eq 1100 ]] && NVCC_REGEX='compute_(3[5-9]|[4-9][0-9])'
 
 declare -a CC_LIST
 IFS=" " read -r -a CC_LIST <<< "$(nvcc "$NVCC_OPTS" | grep -Eoe "$NVCC_REGEX" | cut -d '_' -f2 | $GSORT -un | xargs)"
-if [ ${#CC_LIST[*]} -eq 0 ]; then
+if [[ ${#CC_LIST[*]} -eq 0 ]]; then
   echo "Error: could not parse list of supported compute capabilities" >&2
   exit 3
-elif [ ${#CC_LIST[*]} -lt 3 ]; then
+elif [[ ${#CC_LIST[*]} -lt 3 ]]; then
   echo "Warning: less than three (3) supported compute capabilities" >&2
 fi
 
@@ -80,46 +82,42 @@ for CC in "${CC_LIST[@]}"; do
   sed -i "/^NVCCFLAGS = .*\$/a NVCCFLAGS += --generate-code arch=compute_${CC},code=sm_${CC}" src/Makefile src/Makefile.win
 done
 
-if [ "$CUDA_VER" -ge 1100 ]; then
+if [[ "$CUDA_VER" -ge 1100 ]]; then
   echo 'Adding NVCCFLAGS to allow unsupported MSVC versions...'
   sed -i '/^NVCCFLAGS = .*/a NVCCFLAGS += -allow-unsupported-compiler -D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH' src/Makefile.win
 fi
-if [ "$CUDA_VER" -lt 1200 ]; then
-  echo "Adding libraries to LDFLAGS to support static build on older Ubuntu versions..."
-  sed -i -E 's/^(LDFLAGS = .*? -lcudart_static) (.*)/\1 -ldl -lrt -lpthread \2/' src/Makefile
-fi
 
 echo 'Gathering host compiler and NVCC version info...'
 # COMPILER_VER for Windows builds is actually set to the MSVC product version.
 # We retrieve the cl.exe version during the build step and add it to the table.
 if [[ -x "$(command -v vswhere.exe)" ]]; then
-  CC_VSPROD="$(vswhere -latest -products '*' -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property displayName | sed -e 's/Visual Studio/MSVC/')"
+  CC_VSPROD=$(vswhere -latest -products '*' -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property displayName | sed -e 's/Visual Studio/MSVC/')
   COMPILER_VER="${CC_VSPROD}, $(vswhere -latest -products '*' -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property installationVersion)"
 elif [[ -x "$(command -v powershell.exe)" ]]; then
-  CC_VSINFO="$(powershell -Command Get-VSSetupInstance)"
-  CC_VSPROD="$(echo "$CC_VSINFO" | grep DisplayName | cut -d':' -f2 | xargs | sed -e 's/Visual Studio/MSVC/')"
+  CC_VSINFO=$(powershell -Command Get-VSSetupInstance)
+  CC_VSPROD=$(echo "$CC_VSINFO" | grep DisplayName | cut -d':' -f2 | xargs | sed -e 's/Visual Studio/MSVC/')
   COMPILER_VER="${CC_VSPROD}, $(echo "$CC_VSINFO" | grep InstallationVersion | cut -d':' -f2 | xargs)"
 else
-  COMPILER_VER="$(gcc --version | head -n1)"
+  COMPILER_VER=$(gcc --version | head -n1)
   # shellcheck source=/dev/null
   source /etc/os-release
-  OS_VER="${PRETTY_NAME}"
+  OS_VER=${PRETTY_NAME}
   OS_TYPE="linux64"
 fi
 
 if [[ -x "$(command -v powershell.exe)" ]]; then
-  OS_VER="$(powershell -Command "[System.Environment]::OSVersion.VersionString" | cut -d ' ' -f2-)"
+  OS_VER=$(powershell -Command "[System.Environment]::OSVersion.VersionString" | cut -d ' ' -f2-)
   OS_TYPE="win64"
 fi
 
-NVCC_VER="$(nvcc --version | tail -n1 | sed -E 's/^Build //;s/^Cuda compilation tools, //')"
+NVCC_VER=$(nvcc --version | tail -n1 | sed -E 's/^Build //;s/^Cuda compilation tools, //')
 
 # get mfaktc version from src/params.h
 # match SemVer and GIMPS version strings: https://regex101.com/r/m38d3i/2
-MFAKTC_VER="$(LC_ALL=en_US.utf8 grep -iPo '#define[\s\t]+MFAKTC_VERSION[\s\t]+"v?\d+(?:\.\d+(?:\.\d+)?(?:-\d+)?|\b)(?:-?(?:alpha|beta|pre)\.?(?:\d+)?\b)?' src/params.h | cut -d '"' -f 2)"
+MFAKTC_VER=$(LC_ALL=en_US.utf8 grep -iPo '#define[\s\t]+MFAKTC_VERSION[\s\t]+"v?\d+(?:\.\d+(?:\.\d+)?(?:-\d+)?|\b)(?:-?(?:alpha|beta|pre)\.?(?:\d+)?\b)?' src/params.h | cut -d '"' -f 2)
 
 # Git-formatted version
-GIT_TAG_VER="$(git describe --tags)"
+GIT_TAG_VER=$(git describe --tags)
 
 # Compare MFAKTC_VER with the version extracted from GIT_TAG_VER using tags.
 # If they don't match, throw a warning and use MFAKTC_VER and the short commit
@@ -130,7 +128,7 @@ GIT_TAG_VER="$(git describe --tags)"
 # reference. This gives a shorter BASE_NAME without the commit hash for
 # releases.
 if [[ "$MFAKTC_VER" != "${GIT_TAG_VER:0:${#MFAKTC_VER}}" ]]; then
-  SHA_SHORT="$(git rev-parse --short HEAD)"
+  SHA_SHORT=$(git rev-parse --short HEAD)
   BASE_NAME="mfaktc-${MFAKTC_VER}-${SHA_SHORT}-${OS_TYPE}-cuda${CUDA_VERSION_FULL}"
   echo "Warning: version from 'git describe' (${GIT_TAG_VER}) doesn't begin with MFAKTC_VER (${MFAKTC_VER}) from params.h"
   echo "Using version from params.h and short commit hash (${SHA_SHORT}) for BASE_NAME"

diff --git a/contrib/start-mfaktc.sh b/contrib/start-mfaktc.sh
@@ -51,16 +51,15 @@ LOCK=$APP.lock
 run_on_device() {
     # ensure instance has its own folder
     mkdir -p "device-$1"
-    if ! cd "device-$1"
-    then
+    if ! cd "device-$1"; then
         echo "error: could not enter directory 'device-$1' for device $1" >&2
         exit 1
     fi
 
     # don't run if device is in use
-    exec 200>"$LOCK"
+    exec {LOCK_FD}>"$LOCK"
 
-    if ! flock -n 200; then
+    if ! flock -n "$LOCK_FD"; then
         echo "error: lock file $LOCK exists, mfaktc may already be running on device $1" >&2
         exit 1
     fi
@@ -105,9 +104,9 @@ fi
 
 if [[ $# -eq 0 ]]; then
     # don't run if device is in use
-    exec 200>"$LOCK"
+    exec {LOCK_FD}>"$LOCK"
 
-    if ! flock -n 200; then
+    if ! flock -n "$LOCK_FD"; then
         echo "error: lock file $LOCK exists, mfaktc may already be running" >&2
         exit 1
     fi

diff --git a/src/Makefile b/src/Makefile
@@ -3,14 +3,23 @@ CUDA_DIR = /usr/local/cuda
 CUDA_INCLUDE = -I$(CUDA_DIR)/include/
 CUDA_LIB = -L$(CUDA_DIR)/lib64/
 
+DEBUG = 0
+
 # compiler settings for .c files (CPU)
-CC = gcc
-CFLAGS = -Wall -Wextra -O3 -flto -malign-double -ffunction-sections -fdata-sections -Wl,--gc-sections $(CUDA_INCLUDE)
-CFLAGS_EXTRA_SIEVE = -funroll-all-loops
+CC ?= gcc
+CXX ?= g++
+CFLAGS = -Wall -Wextra $(CUDA_INCLUDE)
+
+ifeq ($(DEBUG), 1)
+  CFLAGS += -g -Og
+else
+  CFLAGS += -O3 -ffast-math -flto -ffunction-sections -fdata-sections
+  CFLAGS_EXTRA_SIEVE = -funroll-all-loops
+endif
 
 # compiler settings for .cu files (GPU)
 NVCC = nvcc
-NVCCFLAGS = $(CUDA_INCLUDE) --ptxas-options=-v -O3 -Wno-deprecated-gpu-targets
+NVCCFLAGS = $(CUDA_INCLUDE) --ptxas-options=-v -Wno-deprecated-gpu-targets
 
 # generate code for compute capabilities - see this table for supported
 # versions: https://en.wikipedia.org/wiki/CUDA#GPUs_supported
@@ -40,11 +49,15 @@ NVCCFLAGS += --generate-code arch=compute_90,code=sm_90 # Hopper GPUs
 NVCCFLAGS += --generate-code arch=compute_120,code=sm_120 # Blackwell GPUs
 
 # pass some options to the C host compiler
-NVCCFLAGS += --compiler-options=-Wall
+ifeq ($(DEBUG), 1)
+  NVCCFLAGS += -g -G -O1 --compiler-options="-Wall -Wextra -Og"
+else
+  NVCCFLAGS += -O3 --compiler-options="-Wall -Wextra -O3"
+endif
 
 # Linker
-LD = gcc
-LDFLAGS = -flto -fPIC -Wl,--gc-sections $(CUDA_LIB) -lcudart_static -lm -lstdc++
+LD = $(CXX)
+LDFLAGS = -flto -Wl,--gc-sections $(CUDA_LIB) -lcudart_static -lm -ldl -lrt -lpthread
 
 INSTALL = install
 

diff --git a/src/Makefile.win b/src/Makefile.win
@@ -1,8 +1,24 @@
+DEBUG = 0
+
 CC = cl
-CFLAGS = /O2 /Oy /W2 /fp:fast /I"$(CUDA_PATH)\include" /I"$(CUDA_PATH)\include\cudart" /nologo
+CFLAGS = /W4 /I"$(CUDA_PATH)\include" /I"$(CUDA_PATH)\include\cudart" /nologo
+
+ifeq ($(DEBUG), 1)
+  CFLAGS += /Od /Zi /RTC1
+else
+  CFLAGS += /O2 /GL /Gw /fp:fast
+endif
 
-NVCCFLAGS = -m64 -O3 --ptxas-options=-v -Wno-deprecated-gpu-targets
-CUFLAGS = -DWIN64 -Xcompiler "/EHsc /W3 /nologo /O2" $(NVCCFLAGS)
+NVCCFLAGS = -m64 --ptxas-options=-v -Wno-deprecated-gpu-targets
+CUFLAGS = -DWIN64 $(NVCCFLAGS)
+
+ifeq ($(DEBUG), 1)
+  NVCCFLAGS += -g -G -O1
+  CUFLAGS += -Xcompiler "/EHsc /W4 /nologo /Od /Zi"
+else
+  NVCCFLAGS += -O3 
+  CUFLAGS += -Xcompiler "/EHsc /W4 /nologo /O2 /Gw"
+endif
 
 ############################################################
 
@@ -29,7 +45,12 @@ NVCCFLAGS += --generate-code arch=compute_120,code=sm_120
 ############################################################
 
 LINK = link
-LFLAGS = /nologo
+
+ifeq ($(DEBUG), 1)
+  LFLAGS = /nologo
+else
+  LFLAGS = /nologo /LTCG /OPT:REF /OPT:ICF
+endif
 
 CSRC  = sieve.c timer.c parse.c read_config.c mfaktc.c checkpoint.c \
 	filelocking.c signal_handler.c output.c crc.c

diff --git a/src/output.c b/src/output.c
@@ -64,6 +64,9 @@ void print_help(char *string)
     printf("  --sleeptest            test sleep functions\n");
 }
 
+#ifdef __GNUC__
+__attribute__ ((format(printf, 2, 3)))
+#endif
 void logprintf(mystuff_t *mystuff, const char *fmt, ...)
 {
     va_list args;

diff --git a/src/output.h b/src/output.h
@@ -20,6 +20,9 @@ along with mfaktc.  If not, see <http://www.gnu.org/licenses/>.
 extern "C" {
 #endif
 void print_help(char *string);
+#ifdef __GNUC__
+__attribute__ ((format(printf, 2, 3)))
+#endif
 void logprintf(mystuff_t *mystuff, const char *fmt, ...);
 
 void print_dez96(int96 a, char *buf);