Runtime exception on Linux: cannot open shared object file: No such file or directory

Using swipl-ld on Ubuntu 12.04 64-bit.

Just compiling, linking and running Jan's very basic example foreign
language interface code as detailed here:

http://www.swi-prolog.org/pldoc/man?section=plld

I find I have to compile with some extra flags to pull in the libs that
seem to be necessary for full compilation/linking. Instead of:

swipl-ld -o calc calc.c calc.pl


I have to use:

swipl-ld -o calc calc.c calc.pl -lgmp -lrt -lm -lncurses -ldl -lunwind


This all seems to compile okay:

% calc.pl compiled 0.00 sec, 2 clauses
% autoloading prolog_codewalk:must_be/2 from /usr/lib/swi-prolog/library/error
% autoloading prolog_codewalk:portray_clause/1 from
/usr/lib/swi-prolog/library/listing
% autoloading prolog_codewalk:clause_info/4 from
/usr/lib/swi-prolog/library/prolog_clause
% autoloading prolog_codewalk:initialization_layout/4 from
/usr/lib/swi-prolog/library/prolog_clause
% autoloading error:assertion/1 from /usr/lib/swi-prolog/library/debug
% autoloading record:member/2 from /usr/lib/swi-prolog/library/lists
% autoloading prolog_source:directory_file_path/3 from
/usr/lib/swi-prolog/library/filesex
% autoloading files_ex:use_foreign_library/2 from
/usr/lib/swi-prolog/library/shlib
% autoloading qsave:current_foreign_library/2 from
/usr/lib/swi-prolog/library/shlib
% autoloading prolog_debug:backtrace/1 from
/usr/lib/swi-prolog/library/prolog_stack
% autoloading oset:reverse/2 from /usr/lib/swi-prolog/library/lists
% autoloading prolog_codewalk:clause_name/2 from
/usr/lib/swi-prolog/library/prolog_clause
% Autoloader: iteration 1 resolved 11 predicates and loaded 12 files
in 0.048 seconds.  Restarting ...
% autoloading files_ex:permission_error/3 from /usr/lib/swi-prolog/library/error
% autoloading files_ex:maplist/2 from /usr/lib/swi-prolog/library/apply
% Autoloader: loaded 11 files in 2 iterations in 0.075 seconds
% halt

It actually runs, and the output is as desired. But at the start there's
always a (seemingly benign) exception/error that gets triggered on
initialization:


> *./calc pi/2**ERROR: /usr/lib/swi-prolog/library/filesex.pl:57: Initialization goal raised exception:
ERROR: '$open_shared_object'/3: files: cannot open shared object file:
No such file or directory*
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1.5707963267948966


I first encountered this while trying to build a much larger project, and
wondered if I had introduced the issue myself. But I stripped things down
to Jan's simple example and it's visible there, too. I googled for similar
problems and saw that other people were having them (albeit with different
libs) but I couldn't really tell from his responses if Jan was saying that
this would be a general issue on Linux, or whether it would be expected
only if you were trying to use specific files:

"You should create a small hierarchy that includes the required
.so files and makes sure that the file-search-path 'foreign'
can find these files.  There are many ways to do that."


The exception doesn't actually cause any issues with program execution so
far as I can tell (in either the example program or my program), but I
never like things I don't fully understand and am wondering if this will
bite me later. If anyone can shed some light on what's going on I'd be
grateful.

KJ
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