ds: @post_loop_do replaces SetPostLoopCallback

This allows us to avoid repeatedly using memory-intensive
anonymous subs in CodeSearchIdx where the callback is assigned
frequently.  Anonymous subs are known to leak memory in old
Perls (e.g. 5.16.3 in enterprise distros) and still expensive in
newer Perls.  So favor the (\&subroutine, @args) form which
allows us to eliminate anonymous subs going forward.

Only CodeSearchIdx takes advantage of the new API at the moment,
since it's the biggest repeat user of post-loop callback
changes.

Getting rid of the subroutine and relying on a global `our'
variable also has two advantages:

1) Perl warnings can detect typos at compile-time, whereas the
   (now gone) method could only detect errors at run-time.

2) `our' variable assignment can be `local'-ized to a scope

1 files changed, 7 insertions, 23 deletions

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index b6eaf2d7..340086fc 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -44,7 +44,7 @@ our (
      $Epoll,                     # Global epoll fd (or DSKQXS ref)
      $ep_io,                     # IO::Handle for Epoll
 
-     $PostLoopCallback,          # subref to call at the end of each loop, if defined (global)
+     @post_loop_do,              # subref + args to call at the end of each loop
 
      $LoopTimeout,               # timeout of event loop in milliseconds
      @Timers,                    # timers
@@ -69,7 +69,7 @@ sub Reset {
                 %DescriptorMap = ();
                 @Timers = ();
                 %UniqTimer = ();
-                $PostLoopCallback = undef;
+                @post_loop_do = ();
 
                 # we may be iterating inside one of these on our stack
                 my @q = delete @Stack{keys %Stack};
@@ -79,7 +79,7 @@ sub Reset {
                 $Epoll = undef; # may call DSKQXS::DESTROY
         } while (@Timers || keys(%Stack) || $nextq || $AWAIT_PIDS ||
                 $ToClose || keys(%DescriptorMap) ||
-                $PostLoopCallback || keys(%UniqTimer));
+                @post_loop_do || keys(%UniqTimer));
 
         $reap_armed = undef;
         $LoopTimeout = -1;  # no timeout by default
@@ -247,11 +247,13 @@ sub PostEventLoop () {
         }
 
         # by default we keep running, unless a postloop callback cancels it
-        $PostLoopCallback ? $PostLoopCallback->(\%DescriptorMap) : 1;
+        @post_loop_do ?  $post_loop_do[0]->(\%DescriptorMap,
+                                        @post_loop_do[1..$#post_loop_do])
+                        : 1
 }
 
 # Start processing IO events. In most daemon programs this never exits. See
-# C<PostLoopCallback> for how to exit the loop.
+# C<post_loop_do> for how to exit the loop.
 sub event_loop (;$$) {
         my ($sig, $oldset) = @_;
         $Epoll //= _InitPoller();
@@ -287,24 +289,6 @@ sub event_loop (;$$) {
         } while (PostEventLoop());
 }
 
-=head2 C<< CLASS->SetPostLoopCallback( CODEREF ) >>
-
-Sets post loop callback function.  Pass a subref and it will be
-called every time the event loop finishes.
-
-Return 1 (or any true value) from the sub to make the loop continue, 0 or false
-and it will exit.
-
-The callback function will be passed two parameters: \%DescriptorMap
-
-=cut
-sub SetPostLoopCallback {
-    my ($class, $ref) = @_;
-
-    # global callback
-    $PostLoopCallback = (defined $ref && ref $ref eq 'CODE') ? $ref : undef;
-}
-
 #####################################################################
 ### PublicInbox::DS-the-object code
 #####################################################################