devel/flang can't link static images

[Steve Kargl]

Testing the new devel/flang port shows a number of issues with the
/usr/local/bin/flang wrapper routine.  The contents of the wrapper are

#!/bin/sh
/usr/local/flang/bin/flang -L/usr/local/flang/lib -lflang -lflangmain \
 -lflangrti -lexecinfo $@

where I have wrapped the long line.

1) Compile only uses the -c option.

% flang -c a.f90
clang-3.9: warning: -lflang: 'linker' input unused
clang-3.9: warning: -lflangmain: 'linker' input unused
clang-3.9: warning: -lflangrti: 'linker' input unused
clang-3.9: warning: -lexecinfo: 'linker' input unused
clang-3.9: warning: argument unused during compilation: '-L/usr/local/flang/lib'

These warnings are complete nonsense and caused by the inclusion of
the libraries on the command line and the -L option.  This noise 
can be suppressed by inclusion of the -w option.

2) The port installs a number modules and include files in 
/usr/local/flang/include.  Flang cannot automatically find these 
files, so simple programs of the form

use iso_fortran_env
print *, real_kinds
end

fail.

% flang -o z a.f90
F90-F-0004-Unable to open MODULE file iso_fortran_env.mod (a.f90: 1)
F90/x86-64 FreeBSD Flang - 1.5 2017-05-01: compilation aborted

This can be fixed by requiring the user to know to add
-I/usr/local/flang/include to her command line.  A better
fix would be to include this option in the wrapper, so flang
can find the intrinsic modules.

3) flang cannot link static images.

% flang -o z -static a.f90 |& grep undefined | wc -l
     105

There are 105 undefined references because required libraries are
missing.  Here's just a few

/usr/ports/devel/flang/work/flang-a9ccdd7/runtime/flangrti/llcrit.c:(.text._mp_copyin_move_multiple+0x17): undefined reference to `__kmpc_global_thread_num'
/usr/ports/devel/flang/work/flang-a9ccdd7/runtime/flangrti/llcrit.c:(.text._mp_copyin_move_multiple+0x45): undefined reference to `__kmpc_threadprivate_cached'
/usr/ports/devel/flang/work/flang-a9ccdd7/runtime/flangrti/llcrit.c:(.text._mp_copyin_move_multiple+0x59): undefined reference to `__kmpc_threadprivate_cached'
/usr/ports/devel/flang/work/flang-a9ccdd7/runtime/flangrti/llcrit.c:(.text._mp_copyin_move_multiple+0x8d): undefined reference to `__kmpc_barrier'

/root/tmp/a-0fe0a5.o: In function `MAIN_':
/root/tmp/a-353577.ll:(.text+0x37): undefined reference to `f90io_print_init'
/root/tmp/a-353577.ll:(.text+0x4b): undefined reference to `_iso_fortran_env_8_'
/root/tmp/a-353577.ll:(.text+0x52): undefined reference to `f90io_ldw_a'
/root/tmp/a-353577.ll:(.text+0x5a): undefined reference to `f90io_ldw_end'

The undefined references with __kmpc prefixes appear to be
contained in /usr/local/flang/lib/libompstub.a.  This library
should probably be included.

-- 
Steve
20170425 https://www.youtube.com/watch?v=VWUpyCsUKR4
20161221 https://www.youtube.com/watch?v=IbCHE-hONow