[Bug middle-end/4210] should not warning with dead code

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=4210

--- Comment #30 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
At the point where the then block starts being processed (and, thus, 
warnings may be given) it wouldn't be known whether there are labels in 
there or not; cf. the discussion in bug 68193 regarding such warnings and 
_Generic.  If you did things based on settings on entry to if (0), you'd 
need some way to end that setting (i.e. restore that from the containing 
block) early on encountering a label (allowing appropriately for nested if 
(0), of course).