On Tue, 19 Jun 2018 at 01:30, Soul Studios wrote: > > > > > It's never called. > > > > I added a call to abort() to that function, and the tests all pass. So > > the function is never used, so GCC never compiles it and doesn't > > notice that the return type is invalid. That's allowed by the > > standard. The compiler is not required to diagnose ill-formed code in > > uninstantiated templates. > > > > > UPDATE: My bad. > The original compiler feature detection on the test suite was broken/not > matching the correct libstdc++ versions. > Hence the emplace_back/emplace_front tests were not running.
Told you so :-P > However, it does surprise me that GCC doesn't check this code. It's a dependent expression so can't be fully checked until instantiated -- and as you've discovered, it wasn't being instantiated. There's a trade-off between compilation speed and doing additional work to check uninstantiated templates with arbitrarily complex expressions in them.
