efriedma added a comment. In D81678#2089041 <https://reviews.llvm.org/D81678#2089041>, @aqjune wrote:
> > @efriedma > > The way that call argument coercion works is unsound in the presence of > > poison. An integer can't be partially poisoned: it's either poison, or not > > poison. We probably need to come up with some safer way to pass > > structs/unions. > > This is true, clang frontend may lower an argument with aggregate type into > one with large int type (such as i64). > However, can poison value be safely generated in C? Paddings or union with > different size may contain undef bits, but not poison. Signed overflow is UB. > Undef value can exist bitwisely, so I think this is an orthogonal issue. In C semantics, an expression can't produce a poison value. As long as variables and allocations are initialized to undef, not poison, there isn't any way to sneak poison into the padding of a variable, so argument passing is sound. So I guess it's not an issue unless we start poisoning uninitialized variables. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D81678/new/ https://reviews.llvm.org/D81678 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
