On 17 November 2015 at 18:36, Paolo Bonzini <pbonz...@redhat.com> wrote: > On 17/11/2015 19:24, Peter Maydell wrote: >> But if "-fwrapv" means "this dialect of C makes shifts of >> negative numbers well defined and OK" then "-1 << 31" >> should be fine and should not provoke a warning (whether in >> a constant expression or not). If that's not what -fwrapv means, >> then we shouldn't be using it as if it did. > > Since we don't use -pedantic, we don't care.
We need to care because the interesting question is "what is GCC guaranteeing to us", not "how can we shut the compiler up". If -fwrapv doesn't silence these warnings that means there's a disconnect between what we think the guarantees are and what the gcc devs think the guarantees are, which is liable to cause trouble in the future. thanks -- PMM
