[commit: ghc] master: rts: Update comment about FreeBSD's unsigned FD_SETSIZE (11c478b)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/11c478b50e2f56174889fadef3a4e51ed95907d3/ghc

>---------------------------------------------------------------

commit 11c478b50e2f56174889fadef3a4e51ed95907d3
Author: Niklas Hambüchen <mail at nh2.me>
Date:   Tue Sep 19 15:11:38 2017 -0400

    rts: Update comment about FreeBSD's unsigned FD_SETSIZE
    
    Reviewers: bgamari, austin, erikd, simonmar
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie
    
    Differential Revision: https://phabricator.haskell.org/D3957


>---------------------------------------------------------------

11c478b50e2f56174889fadef3a4e51ed95907d3
 rts/posix/Select.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/rts/posix/Select.c b/rts/posix/Select.c
index 3d3b70b..270e6ff 100644
--- a/rts/posix/Select.c
+++ b/rts/posix/Select.c
@@ -256,9 +256,14 @@ awaitEvent(bool wait)
       for(tso = blocked_queue_hd; tso != END_TSO_QUEUE; tso = next) {
         next = tso->_link;
 
-      /* On FreeBSD FD_SETSIZE is unsigned. Cast it to signed int
+      /* On older FreeBSDs, FD_SETSIZE is unsigned. Cast it to signed int
        * in order to switch off the 'comparison between signed and
        * unsigned error message
+       * Newer versions of FreeBSD have switched to unsigned int:
+       *   https://github.com/freebsd/freebsd/commit/12ae7f74a071f0439763986026525094a7032dfd
+       *   http://fa.freebsd.cvs-all.narkive.com/bCWNHbaC/svn-commit-r265051-head-sys-sys
+       * So the (int) cast should be removed across the code base once
+       * GHC requires a version of FreeBSD that has that change in it.
        */
         switch (tso->why_blocked) {
         case BlockedOnRead: