From a0860ba700100c0f192ccb5e3be2d4f670e9a958 Mon Sep 17 00:00:00 2001
From: Alexandre Tuleu <alexandre.tuleu.2005@polytechnique.org>
Date: Thu, 21 Nov 2024 15:36:17 +0100
Subject: [PATCH] Allows compilation on older gcc

Gcc version 7 only has access to experimental/filesystem. These simple
modifications allows to discover such situation and link
<experimental/filesystem> to <filesystem>
---
 CMakeLists.txt                | 31 +++++++++++++++++++++++++++++++
 include/argparse/argparse.hpp |  7 +++++++
 2 files changed, 38 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index da38e41..53c5407 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,11 +4,42 @@ project(argparse VERSION 1.4.0 LANGUAGES CXX)
 
 include(GNUInstallDirs)
 
+
+include(CheckCXXSourceCompiles)
+set(CMAKE_REQUIRED_FLAGS "--std=c++17")
+check_cxx_source_compiles(
+  "#include <filesystem>
+int main() {
+std::filesystem::path(\"foo\");
+return 0;
+}"
+  ARGPARSE_HAS_FILESYSTEM)
+if(NOT ARGPARSE_HAS_FILESYSTEM)
+  set(CMAKE_REQUIRED_LIBRARIES "-lstdc++fs")
+  check_cxx_source_compiles(
+    "#include <experimental/filesystem>
+int main() {
+std::experimental::filesystem::path(\"foo\");
+return 0;
+}"
+    ARGPARSE_HAS_EXPERIMENTAL_FILESYSTEM)
+  if(NOT ARGPARSE_HAS_EXPERIMENTAL_FILESYSTEM)
+    message(
+      FATAL_ERROR
+        "Compiler does not have either <filesystem> or <experimental/filesystem> support"
+    )
+  endif()
+endif()
+
 # installing the header-only-library
 add_library(${PROJECT_NAME} INTERFACE)
 add_library(morrisfranken::argparse ALIAS argparse)
 
 target_compile_features(argparse INTERFACE cxx_std_17)
+if(ARGPARSE_HAS_EXPERIMENTAL_FILESYSTEM)
+  target_compile_definitions(argparse INTERFACE "-DARGPARSE_USE_EXPERIMENTAL_FS=1")
+  target_link_libraries(argparse INTERFACE "-lstdc++fs")
+endif()
 target_include_directories(argparse INTERFACE
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
         $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>)
diff --git a/include/argparse/argparse.hpp b/include/argparse/argparse.hpp
index 31b54db..461d9af 100755
--- a/include/argparse/argparse.hpp
+++ b/include/argparse/argparse.hpp
@@ -35,7 +35,14 @@
 #include <memory>              // for allocator, shared_ptr, __shared_ptr_ac...
 #include <optional>            // for optional, nullopt
 #include <stdexcept>           // for runtime_error, invalid_argument
+#ifdef ARGPARSE_USE_EXPERIMENTAL_FS
+#include <experimental/filesystem>
+namespace std {
+	namespace filesystem = experimental::filesystem;
+}
+#else
 #include <filesystem>          // for getting program_name from path
+#endif
 #include <string>              // for string, operator+, basic_string, char_...
 #include <type_traits>         // for declval, false_type, true_type, is_enum
 #include <utility>             // for move, pair