How to copy paste Xcode warnings?
Yes.  If you go to the Issue Navigator (cmd-4), you'll see a list of build warnings and errors.  You can select one from the list and hit cmd-c.  You'll get something like this:


  /Users/dave/Developer/Cocoa/EmptyFoundation/EmptyFoundation.m:180:15:{178:2-178:6}{178:2-178:7}: warning: conversion specifies type 'unsigned long long' but the argument has type 'NSUInteger' (aka 'unsigned long') [-Wformat,7]