mdbx-cmake: rework linking detection for std::filesystem.

CMakeLists.txt

@@ -527,6 +527,11 @@ if(MDBX_BUILD_CXX AND NOT CMAKE_CXX_COMPILER_LOADED)
   message(FATAL_ERROR "MDBX_BUILD_CXX=${MDBX_BUILD_CXX}: The C++ compiler is required to build the C++API.")
 endif()
 
+if(MDBX_BUILD_CXX)
+  # determine library for C++ std::filesystem
+  probe_libcxx_filesystem()
+endif()
+
 # Get version
 fetch_version(MDBX "${CMAKE_CURRENT_SOURCE_DIR}" FALSE)
 message(STATUS "libmdbx version is ${MDBX_VERSION}")

GNUmakefile

@@ -12,13 +12,21 @@ $(info // The GNU Make $(MAKE_VERSION))
 SHELL         := $(shell env bash -c 'echo $$BASH')
 MAKE_VERx3    := $(shell printf "%3s%3s%3s" $(subst ., ,$(MAKE_VERSION)))
 make_lt_3_81  := $(shell expr "$(MAKE_VERx3)" "<" "  3 81")
-ifeq ($(make_lt_3_81),1)
+ifneq ($(make_lt_3_81),0)
 $(error Please use GNU Make 3.81 or above)
 endif
-make_lt_4_1   := $(shell expr "$(MAKE_VERx3)" "<" "  4  1")
+make_ge_4_1   := $(shell expr "$(MAKE_VERx3)" ">=" "  4  1")
 SRC_PROBE_C   := $(shell [ -f mdbx.c ] && echo mdbx.c || echo src/osal.c)
 SRC_PROBE_CXX := $(shell [ -f mdbx.c++ ] && echo mdbx.c++ || echo src/mdbx.c++)
 UNAME         := $(shell uname -s 2>/dev/null || echo Unknown)
+
+define cxx_filesystem_probe
+  int main(int argc, const char*argv[]) {
+    mdbx::filesystem::path probe(argv[0]);
+    if (argc != 1) throw mdbx::filesystem::filesystem_error(std::string("fake"), std::error_code());
+    return mdbx::filesystem::is_directory(probe.relative_path());
+  }
+endef
 #
 ################################################################################
 #
@@ -57,16 +65,16 @@ CXXFLAGS     ?= $(strip $(CXXSTD) $(filter-out -std=gnu11,$(CFLAGS)))
 
 # libraries adn options for linking
 EXE_LDFLAGS  ?= -pthread
-ifeq ($(make_lt_4_1),1)
+ifneq ($(make_ge_4_1),1)
 # don't use variable expansion trick as workaround for bugs of GNU Make before 4.1
 LIBS         ?= $(shell $(uname2libs))
 LDFLAGS      ?= $(shell $(uname2ldflags))
-LIB_STDCXXFS ?= $(shell echo 'int main(void) { MDBX_STD_FILESYSTEM_PATH probe; return probe.is_absolute(); }' | cat mdbx.h++ - | sed $$'1s/\xef\xbb\xbf//' | $(CXX) -x c++ $(CXXFLAGS) -Wno-error - -Wl,--allow-multiple-definition -lstdc++fs $(LIBS) $(LDFLAGS) $(EXE_LDFLAGS) -o /dev/null 2>probe4lstdfs.err >/dev/null && echo '-Wl,--allow-multiple-definition -lstdc++fs')
+LIB_STDCXXFS ?= $(shell echo '$(cxx_filesystem_probe)' | cat mdbx.h++ - | sed $$'1s/\xef\xbb\xbf//' | $(CXX) -x c++ $(CXXFLAGS) -Wno-error - -Wl,--allow-multiple-definition -lstdc++fs $(LIBS) $(LDFLAGS) $(EXE_LDFLAGS) -o /dev/null 2>probe4lstdfs.err >/dev/null && echo '-Wl,--allow-multiple-definition -lstdc++fs')
 else
 # using variable expansion trick to avoid repeaded probes
 LIBS         ?= $(eval LIBS := $$(shell $$(uname2libs)))$(LIBS)
 LDFLAGS      ?= $(eval LDFLAGS := $$(shell $$(uname2ldflags)))$(LDFLAGS)
-LIB_STDCXXFS ?= $(eval LIB_STDCXXFS := $$(shell echo 'int main(void) { MDBX_STD_FILESYSTEM_PATH probe; return probe.is_absolute(); }' | cat mdbx.h++ - | sed $$$$'1s/\xef\xbb\xbf//' | $(CXX) -x c++ $(CXXFLAGS) -Wno-error - -Wl,--allow-multiple-definition -lstdc++fs $(LIBS) $(LDFLAGS) $(EXE_LDFLAGS) -o /dev/null 2>probe4lstdfs.err >/dev/null && echo '-Wl,--allow-multiple-definition -lstdc++fs'))$(LIB_STDCXXFS)
+LIB_STDCXXFS ?= $(eval LIB_STDCXXFS := $$(shell echo '$$(cxx_filesystem_probe)' | cat mdbx.h++ - | sed $$$$'1s/\xef\xbb\xbf//' | $(CXX) -x c++ $(CXXFLAGS) -Wno-error - -Wl,--allow-multiple-definition -lstdc++fs $(LIBS) $(LDFLAGS) $(EXE_LDFLAGS) -o /dev/null 2>probe4lstdfs.err >/dev/null && echo '-Wl,--allow-multiple-definition -lstdc++fs'))$(LIB_STDCXXFS)
 endif
 
 ################################################################################

cmake/compiler.cmake

@@ -826,24 +826,106 @@ macro(setup_compile_flags)
   unset(MODULE_LINKER_FLAGS)
 endmacro(setup_compile_flags)
 
-if(CMAKE_CXX_COMPILER_LOADED)
+macro(probe_libcxx_filesystem)
-  # determine library for std::filesystem
+  if(CMAKE_CXX_COMPILER_LOADED AND NOT DEFINED LIBCXX_FILESYSTEM)
+    list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_11 HAS_CXX11)
+    if(NOT HAS_CXX11 LESS 0)
+      include(CMakePushCheckState)
+      include(CheckCXXSourceCompiles)
+      cmake_push_check_state()
+      set(stdfs_probe_save_libraries ${CMAKE_REQUIRED_LIBRARIES})
+      unset(stdfs_probe_clear_cxx_standard)
+      if(NOT DEFINED CMAKE_CXX_STANDARD)
+        list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_14 HAS_CXX14)
+        list(FIND CMAKE_CXX_COMPILE_FEATURES cxx_std_17 HAS_CXX17)
+        if(NOT HAS_CXX17 LESS 0
+            AND NOT (CMAKE_COMPILER_IS_CLANG AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5))
+          set(CMAKE_CXX_STANDARD 17)
+        elseif(NOT HAS_CXX14 LESS 0)
+          set(CMAKE_CXX_STANDARD 14)
+        else()
+          set(CMAKE_CXX_STANDARD 11)
+        endif()
+        set(stdfs_probe_clear_cxx_standard ON)
+      endif()
+
+      set(stdfs_probe_code [[
+        #if defined(__SIZEOF_INT128__) && !defined(__GLIBCXX_TYPE_INT_N_0) && defined(__clang__) && __clang_major__ < 4
+        #define __GLIBCXX_BITSIZE_INT_N_0 128
+        #define __GLIBCXX_TYPE_INT_N_0 __int128
+        #endif
+
+        #ifndef __has_include
+        #define __has_include(header) (0)
+        #endif
+        #if __has_include(<version>)
+        #include <version>
+        #endif
+        #include <cstdlib>
+        #include <string>
+        #if defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L
+        #include <string_view>
+        #endif
+
+        #if defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L
+        #include <filesystem>
+        #else
+        #include <experimental/filesystem>
+        #endif
+
+        #if (defined(__cpp_lib_filesystem) && __cpp_lib_filesystem >= 201703L && (!defined(__MAC_OS_X_VERSION_MIN_REQUIRED) || __MAC_OS_X_VERSION_MIN_REQUIRED >= 101500) && (!defined(__IPHONE_OS_VERSION_MIN_REQUIRED) || __IPHONE_OS_VERSION_MIN_REQUIRED >= 130100))
+        namespace fs = ::std::filesystem;
+        #elif defined(__cpp_lib_experimental_filesystem) && __cpp_lib_experimental_filesystem >= 201406L
+        namespace fs = ::std::experimental::filesystem;
+        #endif
+
+        int main(int argc, const char*argv[]) {
+          fs::path probe(argv[0]);
+          if (argc != 1) throw fs::filesystem_error(std::string("fake"), std::error_code());
+          return fs::is_directory(probe.relative_path());
+        }
+        ]])
       set(LIBCXX_FILESYSTEM "")
-  if(CMAKE_COMPILER_IS_ELBRUSCXX)
+
-    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 1.26.0)
+      check_cxx_source_compiles("${stdfs_probe_code}" LIBCXX_FILESYSTEM_none)
+      if(LIBCXX_FILESYSTEM_none)
+        message(STATUS "No linking with additional library needed for std::filesystem")
+      else()
+        set(CMAKE_REQUIRED_LIBRARIES ${stdfs_probe_save_libraries} "stdc++fs")
+        check_cxx_source_compiles("${stdfs_probe_code}" LIBCXX_FILESYSTEM_stdcxxfs)
+        if(LIBCXX_FILESYSTEM_stdcxxfs)
           set(LIBCXX_FILESYSTEM "stdc++fs")
-    endif()
+          message(STATUS "Linking with ${LIBCXX_FILESYSTEM} is required for std::filesystem")
-  elseif(CMAKE_COMPILER_IS_CLANG)
+        else()
-    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
+          set(CMAKE_REQUIRED_LIBRARIES ${stdfs_probe_save_libraries} "c++fs")
+          check_cxx_source_compiles("${stdfs_probe_code}" LIBCXX_FILESYSTEM_cxxfs)
+          if(LIBCXX_FILESYSTEM_cxxfs)
+            set(LIBCXX_FILESYSTEM "c++fs")
+            message(STATUS "Linking with ${LIBCXX_FILESYSTEM} is required for std::filesystem")
+          else()
+            set(CMAKE_REQUIRED_LIBRARIES ${stdfs_probe_save_libraries} "c++experimental")
+            check_cxx_source_compiles("${stdfs_probe_code}" LIBCXX_FILESYSTEM_cxxexperimental)
+            if(LIBCXX_FILESYSTEM_cxxexperimental)
               set(LIBCXX_FILESYSTEM "c++experimental")
-    elseif(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+              message(STATUS "Linking with ${LIBCXX_FILESYSTEM} is required for std::filesystem")
-      set(LIBCXX_FILESYSTEM "stdc++fs")
+            else()
+              message(STATUS "No support for std::filesystem")
             endif()
-  elseif(CMAKE_COMPILER_IS_GNUCXX AND NOT MINGW)
-    if(NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.3 AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
-      set(LIBCXX_FILESYSTEM "stdc++fs")
           endif()
         endif()
       endif()
 
+      set(CMAKE_REQUIRED_LIBRARIES ${stdfs_probe_save_libraries})
+      if(stdfs_probe_clear_cxx_standard)
+        unset(CMAKE_CXX_STANDARD)
+      endif()
+      unset(stdfs_probe_clear_cxx_standard)
+      unset(stdfs_probe_save_libraries)
+      unset(stdfs_probe_code)
+      unset(stdfs_probe_rc)
+      cmake_pop_check_state()
+    endif()
+  endif()
+endmacro(probe_libcxx_filesystem)
+
 cmake_policy(POP)

test/CMakeLists.txt

@@ -31,6 +31,7 @@ set(LIBMDBX_TEST_SOURCES
   )
 
 if(NOT MDBX_BUILD_CXX)
+  probe_libcxx_filesystem()
   list(APPEND LIBMDBX_TEST_SOURCES "${MDBX_SOURCE_DIR}/mdbx.c++" ../mdbx.h++)
 endif()