Thanks Susan, great info. It probably is safe, but we’re pitting the cherries for our latest barrel brew.
Hi Tom, Depending on what I was making - I pit the cherries - but this is solely based on the flavors that are derived - you will get a fresher cherry flavor if pitted and you will get a softer cherry/vanilla/almond flavor with the pits left in which increases the longer they are on the pits - if left on the pits too long - it is almost harsh - so, yes, for a barrel where you will most likely leave it for awhile, I would remove the pits.
So now for this advice - please send a bottle of the final barrel project. ;D
If it’s any good, I’ll bring a keg to NHC. 
I’ll be waiting!
I currently have .25 lbs of Mahleb in a Kriek beer digesting away in a 50 liter Oak cask
with B. Lambicus, (cmon cherry BOMB). Samples were very pie cherry and mahleb lending
some floral notes…just waiting for the brett to work it’s magic.