Steps to reproduce:
1. have an empty bookmarks list;
2. Go to OS X 10.11.2 Documentation > Data Management > File Management > Guides > File System Programming Guide
3. Click on the icon on the right side of the search bar and choose Add Bookmark.
Xcode closes instantly. When I reopen it, I see that there are 2 bookmarks with the same name. If I delete one of them, the other one gets deleted as well, and the issue is replicable once again.
Anyone experiencing that? I'm using Xcode 7.2
for anyone who finds this thread (raxon has probably moved on to other things, ha ha), the solution is simple: update safari.
i am running yosemite for the forseeable future, and while i did not want to update (roger mcnamee is a loser who sniffs every possible byte. freakin' cokehead), i realised that the documentation browser uses safari.
my problem was similar to the above except that my Xcode (7.2) would crash upon trying to bookmark an item. i was using safari 9.x at the time.
after updating to safari 10.x, the bookmarks are now functional.
hth.
sorry one more thing:
a better first measure would have been (if i could do it over again):
try:
rm ~/Library/Caches/com.apple.dt.Xcode/Cache.dbhope this helps even more.