Hi zentara,

For MCE::Shared, the use of IO::FDPass applies to Condvar, Queue and to mce_open when constructing a shared handle from a non-shared handle not yet knowed to the shared-manager process. IO::FDpass isn't used for anything else.

   use MCE::Shared;

   # starting the shared-manager, implicitly
   my $ca = MCE::Shared->cache( max_keys => 500 );

   # or starting early, explicitly
   MCE::Shared->start();

   # at this point, IO::FDPass is necessary for constructing
   # a shared condvar or queue, passing fd descriptor

   # ... for new socket handle made during construction
   # workers block using a socket handle for ->wait, ->timedwait
   # the shared-manager unblocks by writing to _cw_sock

   my $cv = MCE::Shared->condvar();  # _cw_sock

   # ... for new socket handles made during construction
   # workers block using socket handles for ->dequeue, ->await
   # the shared-manager unblocks by writing to _qw_sock, _aw_sock

   my $q1 = MCE::Shared->queue();  # _qw_sock
   my $q2 = MCE::Shared->queue( await => 1 );  # _aw_sock
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Without IO::FDPass, one cannot construct a shared condvar or queue while the shared manager is running. The work around is to construct these before other shared objects (e.g. ->array, ->hash, etc). Then, start the shared-manager manually.

   use MCE::Shared;

   my $cv  = MCE::Shared->condvar(0);
   my $que = MCE::Shared->queue( fast => 1 );

   MCE::Shared->start() # must start manually

   my $hash = MCE::Shared->hash(); # or implicitly
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Note: MCE starts the shared-manager if not started. Ditto for MCE::Hobo because that constructs two shared hashes.

Regarding mce_open, IO::FDPass is needed when constructing a shared-handle from a non-shared handle not yet available inside the shared-manager process. The workaround is having the non-shared handle made before the shared-manager process is started implicitly or explicitly.

   # the shared-manager knows of \*STDIN, \*STDOUT, \*STDERR

   mce_open my $shared_in,  "<",  \*STDIN;   # ok
   mce_open my $shared_out, ">>", \*STDOUT;  # ok
   mce_open my $shared_err, ">>", \*STDERR;  # ok

   # but may not know of $non_shared_fh

   mce_open my $shared_fh, ">>", $non_shared_fh;
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Regards, Mario