[Bug c/79479] -Woverflow false alarm in unreachable expression

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79479

--- Comment #10 from joseph at codesourcery dot com <joseph at codesourcery dot 
com> ---
This is arguably the same as or similar to bug 4210 and its duplicates.