From e46716472a8bd30cc3b21f90a1f4b204dac341e1 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Mon, 6 May 2019 13:02:15 +1000
Subject: [PATCH] Revert "cxx: remove test for the filesystem library"

This reverts commit 874bbb2413ac9cd54c03d6e358623e669042264f.
---
 nc_cxx.cmake | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/nc_cxx.cmake b/nc_cxx.cmake
index 1b782a3..b41d1a7 100644
--- a/nc_cxx.cmake
+++ b/nc_cxx.cmake
@@ -33,6 +33,39 @@ append_compile_flag ("/std:c++latest")
 # libstdc++ headers don't behave well under c++17/clang.
 append_compile_flag ("-stdlib=libc++")
 
+###############################################################################
+# find the gcc or clang filesystem library and append to libs if needed
+#
+# note, we specifically _cannot_ use find_library because it just makes wild
+# hardcoded guess and doesn't respect _all_ the system paths; specifically
+# something like /usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libstdc++.so won't get
+# discovered.
+if (NOT DEFINED __nc_cxx_stdcxxfs)
+    foreach(lib "" "c++fs" "c++experimental" "stdc++fs")
+        if (NOT __nc_cxx_stdcxxfs)
+            message (STATUS "Trying c++fs library '${lib}'")
+            try_compile(
+                __nc_cxx_stdcxxfs ${CMAKE_CURRENT_BINARY_DIR}
+            SOURCES
+                ${CMAKE_CURRENT_SOURCE_DIR}/cmake/nc_cxx_stdcxxfs.cpp
+            LINK_LIBRARIES
+                ${lib})
+
+            if (__nc_cxx_stdcxxfs)
+                set (__nc_cxx_stdcxxfs "${lib}" CACHE INTERNAL "library required for c++ filesystem")
+            endif ()
+        endif ()
+    endforeach()
+
+    if (NOT __nc_cxx_stdcxxfs)
+        message (FATAL_ERROR "Could not locate the required c++fs library")
+    endif ()
+
+    message (STATUS "Using c++fs library ${__nc_cxx_stdcxxfs}")
+endif ()
+
+set(NC_CXX_STDCXXFS ${__nc_cxx_stdcxxfs})
+
 
 ###############################################################################
 test_restrict(RESTRICT_KEYWORD)