[MacPorts] #59805: FileZilla @3.46.0: fatal error: 'optional' file not found

[MacPorts]

#59805: FileZilla @3.46.0: fatal error: 'optional' file not found
------------------------+-----------------------
 Reporter:  ryandesign  |      Owner:  lhaeger
     Type:  defect      |     Status:  assigned
 Priority:  Normal      |  Milestone:
Component:  ports       |    Version:  2.6.2
 Keywords:              |       Port:  FileZilla
------------------------+-----------------------
 Even though FileZilla now specifies that it requires C++17, it
 [https://build.macports.org/builders/ports-10.13_x86_64-builder/builds/73020/steps
 /install-port/logs/stdio fails to build] on 10.13 and earlier with:

 {{{
 In file included from asksavepassworddialog.cpp:3:
 In file included from ./Options.h:12:
 In file included from ./xmlfunctions.h:16:
 ./serverdata.h:8:10: fatal error: 'optional' file not found
 #include <optional>
          ^~~~~~~~~~
 1 error generated.
 In file included from asyncrequestqueue.cpp:3:
 In file included from ./asyncrequestqueue.h:4:
 In file included from ./context_control.h:5:
 In file included from ./state.h:5:
 In file included from ./sitemanager.h:6:
 In file included from ./xmlfunctions.h:16:
 ./serverdata.h:8:10: fatal error: 'optional' file not found
 #include <optional>
          ^~~~~~~~~~
 make[4]: *** [filezilla-asksavepassworddialog.o] Error 1
 make[4]: *** Waiting for unfinished jobs....
 In file included from auto_ascii_files.cpp:3:
 In file included from ./Options.h:12:
 In file included from ./xmlfunctions.h:16:
 ./serverdata.h:8:10: fatal error: 'optional' file not found
 #include <optional>
          ^~~~~~~~~~
 1 error generated.
 make[4]: *** [filezilla-auto_ascii_files.o] Error 1
 In file included from bookmarks_dialog.cpp:2:
 In file included from ./bookmarks_dialog.h:5:
 ./serverdata.h:8:10: fatal error: 'optional' file not found
 #include <optional>
          ^~~~~~~~~~
 In file included from aboutdialog.cpp:6:
 In file included from ./Options.h:12:
 In file included from ./xmlfunctions.h:16:
 ./serverdata.h:8:10: fatal error: 'optional' file not found
 #include <optional>
          ^~~~~~~~~~
 1 error generated.
 make[4]: *** [filezilla-asyncrequestqueue.o] Error 1
 1 error generated.
 make[4]: *** [filezilla-aboutdialog.o] Error 1
 1 error generated.
 make[4]: *** [filezilla-bookmarks_dialog.o] Error 1
 }}}

 Maybe MacPorts base's minimum C++17-supporting clang version information
 is wrong and needs to be corrected.

 But in searching for this problem I have also read that it might be a
 feature implemented only in newer versions of libc++. If so, I don't know
 what we do, since libc++ is provided by macOS and we do not have a way to
 update it.

-- 
Ticket URL: <https://trac.macports.org/ticket/59805>
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