Does not compile on Freebsd

[devosalain]

nim cpp test.nim returns
Hint: used config file '/usr/local/etc/nim/nim.cfg' [Conf]
........
/usr/home/x/Dirs/Src/Nim/nfltk/private/image.nim(83, 22) Warning: use csize_t instead; csize is deprecated [Deprecated]
/usr/home/x/Dirs/Src/Nim/nfltk/private/image.nim(84, 19) Warning: use csize_t instead; csize is deprecated [Deprecated]
/usr/home/x/Dirs/Src/Nim/nfltk/private/widget.nim(10, 18) Warning: use csize_t instead; csize is deprecated [Deprecated]
/usr/home/x/Dirs/Src/Nim/nfltk/private/widget.nim(11, 19) Warning: use csize_t instead; csize is deprecated [Deprecated]
/usr/home/x/Dirs/Src/Nim/nfltk/private/widget.nim(10, 18) Warning: use csize_t instead; csize is deprecated [Deprecated]
/usr/home/x/Dirs/Src/Nim/nfltk/private/widget.nim(11, 19) Warning: use csize_t instead; csize is deprecated [Deprecated]
...
/usr/home/x/Dirs/Src/Nim/nfltk/private/input.nim(113, 40) Warning: use csize_t instead; csize is deprecated [Deprecated]
.................CC: stdlib_system.nim
CC: private/enumerations.nim
CC: private/nimwidget.nim
CC: test.nim
/home/x/.cache/nim/test_d/@[email protected]:32:1: error: visibility does not match previous declaration
N_LIB_PRIVATE Fl_Fontsize FL_NORMAL_SIZE;
^
/usr/local/lib/nim/nimbase.h:194:40: note: expanded from macro 'N_LIB_PRIVATE'

define N_LIB_PRIVATE attribute((visibility("hidden")))

                                   ^

/usr/local/include/FL/Enumerations.H:906:8: note: previous attribute is here
extern FL_EXPORT Fl_Fontsize FL_NORMAL_SIZE; ///< normal font size
^
/usr/local/include/FL/Fl_Export.H:33:39: note: expanded from macro 'FL_EXPORT'

define FL_EXPORT attribute ((visibility ("default")))

                                  ^

1 error generated.

Error: execution of an external compiler program 'clang++ -c -std=gnu++14 -funsigned-char -I/usr/local/lib/nim -I/usr/local/include -I/usr/local/include -I/usr/home/x/Dirs/Src/Nim/nfltk -o /home/x/.cache/nim/test_d/@[email protected] /home/x/.cache/nim/test_d/@[email protected]' failed with exit code: 1

HOST:x: /home/x/Dirs/Src/Nim/nfltk >