Yes Jim, exactly. I also sent the wrong link at least once, but this was my point. In the absence of compiler support I think it is actually possible to implement this anyway using syntax 1 but that is left as an exercise to the reader.
On Mon, Jan 9, 2017 at 10:20 AM, Jim Apple <[email protected]> wrote: > Though the attribute is "on" the definition, it can't appear in that > location (after parameters, before curly braces). I don't know why. > > I think I now understand what you were saying above: if we use > WARN_UNUSED_RESULT, then it can go after the function for functions > with prototypes but must go earlier in the line for functions without > prototypes. > > Did I get that right? > > On Mon, Jan 9, 2017 at 10:11 AM, Zachary Amsden <[email protected]> > wrote: > > Maybe I'm just being dense but I couldn't get it to work with syntax 2 > on a > > function definition without having a separate forward declaration: > > > > https://godbolt.org/g/ODtoQC vs. https://godbolt.org/g/WCxDZv > > (non-functional) > > > > - Zach > > > > On Mon, Jan 9, 2017 at 10:00 AM, Jim Apple <[email protected]> wrote: > > > >> That's applying it to the type definition. At the type use: > >> > >> https://godbolt.org/g/RMYVW7 > >> > >> On Mon, Jan 9, 2017 at 9:56 AM, Zachary Amsden <[email protected]> > >> wrote: > >> > GCC doesn't catch this when optimization is enabled and the result is > >> > discarded: > >> > > >> > https://godbolt.org/g/4b0BQC > >> > > >> > I think that means a type wrapper approach is needed, which probably > >> > necessitates option 1. > >> > > >> > - Zach > >> > > >> > On Mon, Jan 9, 2017 at 9:17 AM, Jim Apple <[email protected]> > wrote: > >> > > >> >> My vote, as I mentioned on the patch, is option 1. I see MUST_USE(T) > >> >> as a property of T, like const T or volatile T. I think it is dual to > >> >> move semantics or to Rust's ability to temporarily or permanently > >> >> consume values so that /only/ one copy is in use rather than > >> >> MUST_USE's /at least one/. > >> >> > >> >> https://en.wikipedia.org/wiki/Substructural_type_system > >> >> > >> >> On Fri, Jan 6, 2017 at 4:05 PM, Taras Bobrovytsky > >> >> <[email protected]> wrote: > >> >> > I'd vote for #2. I think it's better to have less important > >> information > >> >> > (such as qualifiers) towards the end of lines. (I think it would be > >> nice > >> >> if > >> >> > modifiers such as public and private were at the end of method > >> >> declarations > >> >> > in Java, for example: void myMethod() private static {...}) > >> >> > > >> >> > On Fri, Jan 6, 2017 at 3:38 PM, Daniel Hecht <[email protected]> > >> >> wrote: > >> >> > > >> >> >> As I indicated in the original review, my preference is #2 but I > >> don't > >> >> feel > >> >> >> too strongly. > >> >> >> > >> >> >> On Fri, Jan 6, 2017 at 2:59 PM, Tim Armstrong < > >> [email protected]> > >> >> >> wrote: > >> >> >> > >> >> >> > Hi All, > >> >> >> > I wanted to poll the Impala community for opinions about style > >> for > >> >> >> > declaring functions where the caller is expected to do something > >> with > >> >> the > >> >> >> > return value. > >> >> >> > > >> >> >> > Ideally we'd be able to declare Status with an attribute that > made > >> >> this > >> >> >> > take effect globally, but unfortunately that's not available > until > >> >> C++17. > >> >> >> > > >> >> >> > So we need to annotate each Status-returning function. The two > >> >> >> alternatives > >> >> >> > we discussed on this CR (https://gerrit.cloudera.org/#/c/4878/) > >> were: > >> >> >> > > >> >> >> > #1 - a special macro wrapping Status > >> >> >> > > >> >> >> > MUST_USE(Status) DoSomethingThatCanFail(int64_t foo, Bar* bar); > >> >> >> > > >> >> >> > Pros: > >> >> >> > * Closely connected to the return type that it affects > >> >> >> > * It's easier to search/replace Status with MUST_USE(Status) > >> >> >> > > >> >> >> > Cons: > >> >> >> > * Could get visually noisy if we use it everywhere > >> >> >> > > >> >> >> > #2 - a macro that gets appended to the declaration: > >> >> >> > > >> >> >> > Status DoSomethingThatCanFail(int64_t foo, Bar* bar) > >> >> WARN_UNUSED_RESULT; > >> >> >> > > >> >> >> > Pros: > >> >> >> > * Macro is slightly > >> >> >> > * Less visually noisy since it's at the end of the declaration > >> >> >> > > >> >> >> > What do people think? > >> >> >> > > >> >> >> > >> >> > >> >
