Re: [PATCH 2/2] Better system header location detection for built-in macro tokens

[Jason Merrill]

What if the built-in macro appears in a macro defined in a system header 
but used in user code?  This would resolve the location all the way to 
the user code, and warn.  I think we only want to step out until we 
reach a non-built-in macro, not all the way to the outermost expansion 
point.

Jason