fix(compat): Add drop-in std::filesystem header for older systems

Signed-off-by: Steffen Vogel <steffen.vogel@opal-rt.com>

Author: stv0g

CMakeLists.txt

@@ -76,19 +76,16 @@ find_package(Lua)
 find_package(LibDataChannel)
 find_package(re)
 find_package(OpenDSSC)
+find_package(FileSystem)
 
 # Check for tools
+find_program(PROTOBUFC_COMPILER NAMES protoc-c)
+find_program(PROTOBUF_COMPILER NAMES protoc)
 find_program(PASTE NAMES paste)
 if(NOT PASTE)
     message(SEND_ERROR "GNU paste is missing. Please install coreutils")
 endif()
 
-# Check programs
-find_program(PROTOBUFC_COMPILER NAMES protoc-c)
-find_program(PROTOBUF_COMPILER NAMES protoc)
-
-# Build without any GPL-code
-option(WITHOUT_GPL "Build VILLASnode without any GPL code" OFF)
 
 set(ENV{PKG_CONFIG_PATH} "$ENV{PKG_CONFIG_PATH}:/usr/local/lib/pkgconfig:/usr/local/lib64/pkgconfig:/usr/local/share/pkgconfig:/usr/lib64/pkgconfig")
 
@@ -157,7 +154,15 @@ else()
     set(FOUND_FPGA_SUBMODULES OFF)
 endif()
 
+if(CXX17_FILESYSTEM)
+    set(STDCXX_FS_NOT_FOUND OFF)
+else()
+    set(STDCXX_FS_NOT_FOUND ON)
+endif()
+
 # Build options
+cmake_dependent_option(WITHOUT_GPL          "Build VILLASnode without any GPL code"                 OFF                "" ON)
+cmake_dependent_option(WITH_GHC_FS          "Build using ghc::filesystem, a drop in replacement for std::filesystem"  ON "STDCXX_FS_NOT_FOUND" OFF)
 cmake_dependent_option(WITH_DEFAULTS        "Defaults for non required build options"               ON                 "" OFF)
 
 cmake_dependent_option(WITH_API             "Build with remote control API"                         "${WITH_DEFAULTS}" "" OFF)
@@ -206,7 +211,7 @@ cmake_dependent_option(WITH_NODE_WEBSOCKET  "Build with websocket node-type"
 cmake_dependent_option(WITH_NODE_ZEROMQ     "Build with zeromq node-type"                           "${WITH_DEFAULTS}" "LIBZMQ_FOUND; NOT WITHOUT_GPL" OFF)
 cmake_dependent_option(WITH_NODE_OPENDSS    "Build with opendss node-type"                          "${WITH_DEFAULTS}" "OpenDSSC_FOUND" OFF)
 
-# set a default for the build type
+# Set a default for the build type
 if("${CMAKE_BUILD_TYPE}" STREQUAL "")
     set(CMAKE_BUILD_TYPE "Debug")
 endif()
@@ -227,6 +232,11 @@ else()
     add_compile_options(-Wno-error)
 endif()
 
+if(WITH_GHC_FS)
+    find_package(ghc_filesystem 1.5.14 REQUIRED)
+    include_directories($<TARGET_PROPERTY:ghcFilesystem::ghc_filesystem,INTERFACE_INCLUDE_DIRECTORIES>)
+endif()
+
 # Get version info and buildid from Git
 GetVersion(${PROJECT_SOURCE_DIR} "CMAKE_PROJECT")
 

cmake/FindFileSystem.cmake

@@ -0,0 +1,21 @@
+# CMakeLists.txt.
+#
+# Author: Steffen Vogel <post@steffenvogel.de>
+# SPDX-FileCopyrightText: 2025 Steffen Vogel <steffen.vogel@opal-rt.com>
+# SPDX-License-Identifier: Apache-2.0
+
+set(FILESYSTEM_TEST_CODE "
+#include <filesystem>
+
+int main(void) {
+	return std::filesystem::is_regular_file(\"/\") ? 0 : 1;
+}
+")
+
+include(CMakePushCheckState)
+
+cmake_push_check_state(RESET)
+check_cxx_source_compiles("${FILESYSTEM_TEST_CODE}" CXX17_FILESYSTEM)
+cmake_pop_check_state()
+
+unset(FILESYSTEM_TEST_CODE)

common/include/villas/config.hpp.in

@@ -53,5 +53,6 @@
 
 // Library features
 #cmakedefine FMT_LEGACY_OSTREAM_FORMATTER
+#cmakedefine WITH_GHC_FS
 
 // clang-format on

common/include/villas/fs.hpp

@@ -0,0 +1,15 @@
+/* std::filesystem compatability
+ *
+ * SPDX-FileCopyrightText: 2025, ghc::filesystem Authors
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <villas/config.hpp>
+
+#ifdef WITH_GHC_FS
+    #include <ghc/filesystem.hpp>
+    namespace fs = ghc::filesystem;
+#else
+    #include <filesystem>
+    namespace fs = std::filesystem;
+#endif

common/include/villas/kernel/devices/device.hpp

@@ -8,9 +8,9 @@
 
 #pragma once
 
-#include <filesystem>
 #include <optional>
 
+#include <villas/fs.hpp>
 #include <villas/kernel/devices/driver.hpp>
 
 namespace villas {
@@ -24,8 +24,8 @@ class Device {
   virtual std::optional<std::unique_ptr<Driver>> driver() const = 0;
   virtual std::optional<int> iommu_group() const = 0;
   virtual std::string name() const = 0;
-  virtual std::filesystem::path override_path() const = 0;
-  virtual std::filesystem::path path() const = 0;
+  virtual fs::path override_path() const = 0;
+  virtual fs::path path() const = 0;
   virtual void probe() const = 0;
 };
 

common/include/villas/kernel/devices/ip_device.hpp

@@ -8,9 +8,9 @@
 
 #pragma once
 
-#include <filesystem>
 #include <vector>
 
+#include <villas/fs.hpp>
 #include <villas/kernel/devices/platform_device.hpp>
 
 namespace villas {
@@ -19,21 +19,21 @@ namespace devices {
 
 class IpDevice : public PlatformDevice {
 public:
-  static IpDevice from(const std::filesystem::path unsafe_path);
-  static bool is_path_valid(const std::filesystem::path unsafe_path);
+  static IpDevice from(const fs::path unsafe_path);
+  static bool is_path_valid(const fs::path unsafe_path);
 
 private:
   IpDevice() = delete;
   IpDevice(
-      const std::filesystem::path valid_path) //! Dont allow unvalidated paths
+      const fs::path valid_path) //! Dont allow unvalidated paths
       : PlatformDevice(valid_path){};
 
 public:
   size_t addr() const;
   std::string ip_name() const;
 
   static std::vector<villas::kernel::devices::IpDevice>
-  from_directory(std::filesystem::path devices_directory);
+  from_directory(fs::path devices_directory);
 };
 
 } // namespace devices

common/include/villas/kernel/devices/linux_driver.hpp

@@ -8,10 +8,10 @@
 
 #pragma once
 
-#include <filesystem>
 #include <fstream>
 #include <iostream>
 
+#include <villas/fs.hpp>
 #include <villas/kernel/devices/driver.hpp>
 
 namespace villas {
@@ -24,20 +24,20 @@ class LinuxDriver : public Driver {
   static constexpr char UNBIND_DEFAULT[] = "unbind";
 
 public:
-  const std::filesystem::path path;
+  const fs::path path;
 
 private:
-  const std::filesystem::path bind_path;
-  const std::filesystem::path unbind_path;
+  const fs::path bind_path;
+  const fs::path unbind_path;
 
 public:
-  LinuxDriver(const std::filesystem::path path)
-      : LinuxDriver(path, path / std::filesystem::path(BIND_DEFAULT),
-                    path / std::filesystem::path(UNBIND_DEFAULT)){};
+  LinuxDriver(const fs::path path)
+      : LinuxDriver(path, path / fs::path(BIND_DEFAULT),
+                    path / fs::path(UNBIND_DEFAULT)){};
 
-  LinuxDriver(const std::filesystem::path path,
-              const std::filesystem::path bind_path,
-              const std::filesystem::path unbind_path)
+  LinuxDriver(const fs::path path,
+              const fs::path bind_path,
+              const fs::path unbind_path)
       : path(path), bind_path(bind_path), unbind_path(unbind_path){};
 
 public:

common/include/villas/kernel/devices/platform_device.hpp

@@ -8,8 +8,7 @@
 
 #pragma once
 
-#include <filesystem>
-
+#include <villas/fs.hpp>
 #include <villas/kernel/devices/device.hpp>
 #include <villas/kernel/devices/driver.hpp>
 
@@ -23,27 +22,27 @@ class PlatformDevice : public Device {
   static constexpr char OVERRIDE_DEFAULT[] = "driver_override";
 
 private:
-  const std::filesystem::path m_path;
-  const std::filesystem::path m_probe_path;
-  const std::filesystem::path m_override_path;
+  const fs::path m_path;
+  const fs::path m_probe_path;
+  const fs::path m_override_path;
 
 public:
-  PlatformDevice(const std::filesystem::path path)
-      : PlatformDevice(path, std::filesystem::path(PROBE_DEFAULT),
-                       path / std::filesystem::path(OVERRIDE_DEFAULT)){};
+  PlatformDevice(const fs::path path)
+      : PlatformDevice(path, fs::path(PROBE_DEFAULT),
+                       path / fs::path(OVERRIDE_DEFAULT)){};
 
-  PlatformDevice(const std::filesystem::path path,
-                 const std::filesystem::path probe_path,
-                 const std::filesystem::path override_path)
+  PlatformDevice(const fs::path path,
+                 const fs::path probe_path,
+                 const fs::path override_path)
       : m_path(path), m_probe_path(probe_path),
         m_override_path(override_path){};
 
   // Implement device interface
   std::optional<std::unique_ptr<Driver>> driver() const override;
   std::optional<int> iommu_group() const override;
   std::string name() const override;
-  std::filesystem::path override_path() const override;
-  std::filesystem::path path() const override;
+  fs::path override_path() const override;
+  fs::path path() const override;
   void probe() const override;
 };
 

common/include/villas/utils.hpp

@@ -11,7 +11,6 @@
 #include <cassert>
 #include <cstdint>
 #include <cstdlib>
-#include <filesystem>
 #include <list>
 #include <string>
 #include <vector>
@@ -21,6 +20,7 @@
 #include <signal.h>
 #include <sys/types.h>
 
+#include <villas/fs.hpp>
 #include <villas/config.hpp>
 
 #ifdef __GNUC__
@@ -212,9 +212,9 @@ template <class... Ts> struct overloaded : Ts... {
 // Explicit deduction guide (not needed as of C++20)
 template <class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
 
-void write_to_file(std::string data, const std::filesystem::path file);
+void write_to_file(std::string data, const fs::path file);
 std::vector<std::string>
-read_names_in_directory(const std::filesystem::path &directory);
+read_names_in_directory(const fs::path &directory);
 
 namespace base64 {
 

common/lib/kernel/devices/device_connection.cpp

@@ -27,7 +27,7 @@ DeviceConnection DeviceConnection::from(
 
   // Bind the devicetree device to vfio driver
   LinuxDriver driver(
-      std::filesystem::path("/sys/bus/platform/drivers/vfio-platform"));
+      fs::path("/sys/bus/platform/drivers/vfio-platform"));
   driver.attach(device);
 
   // Attach vfio container to the iommu group