On Wed, Jan 29, 2020 at 01:46:55AM +0100, Jiri Kosina wrote: > On Tue, 28 Jan 2020, Josh Poimboeuf wrote: > > > > Anyway, I think that we might make your life easier with using the > > > proposed -Wsuggest-attribute=noreturn. > > > > Maybe. Though if I understand correctly, this doesn't help for any of > > the new warnings because they're for static functions, and this only > > warns about global functions. > > Could you please provide a pointer where those have been > reported/analyzed? > > For the cases I've seen so far, it has always been gcc deciding under > certain circumstances not to propagate __attribute__((__noreturn__)) from > callee to caller even in the cases when caller unconditionally called > callee. > > AFAIU, the behavior is (and always will) be dependent on the state of gcc > optimizations, and therefore I don't see any other way than adding > __noreturn anotation transitively everywhere in order to silence objtool. > > So those cases have to be fixed anyway. > > What are the other cases please? Either I have completely missed those, or > they haven't been mentioned in this thread. For example, see: https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/commit/?h=objtool-fixes&id=6265238af90b395a1e5e5032a41f012a552d8a9e Many of those callees are static noreturns, for which we've *never* needed annotations. Disabling -fipa-pure-const has apparently changed that. -Wsuggest-attribute=noreturn doesn't seem to suggest annotations for static functions, probably because most reasonable setups use -O2 which allows GCC to detect them. -- Josh
