https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102223
--- Comment #6 from Federico Kircheis <federico.kircheis at gmail dot com> --- > are you expecting this to go under an existing warning flag, or a new one? Ideally -Wall, but there might already be some flags related to dangling pointers and references. > Your compiler explorer link doesn't enable optimizations. That's true, but if you look at the assembly there is no function call to std::move, thus I assumed that contrary to another (non-inline) function call, a diagnostic would have been possible even without optimizations. But there is no warning even with optimizations enabled. > I assume you already know this, but the original testcase in comment 0 is > perfectly valid. The static_cast creates a new temporary, which *does* get > its lifetime extended. Yes, should have made it clearer in comment #1, sorry. Unfortunately I realized after I wrote the message that I copied the wrong snippet (and typed thus a wrong explanation), and I could not edited it. > With inlining, in theory it would be possible to diagnose the invalid access, > but other compilers don't do it either. It would be nice, but I'm not sure > it's likely to happen any time soon. I noticed too that other compiler do not do this diagnostic. Too bad. > GCC doesn't even get it right in constexpr contexts, see PR 70331 and the > linked bugs in the See Also field. Ouch. > PR 96780 comment 2 could potentially help for the specific case of std::move, > but not the general case. AS I had a discussion explicitly about std::move/xvalues and lifetime extension, I'll say it's a good start. And it confused me until I realized std::move is a function, and thus obviously destroys lifetime extension in the example I gave, while the cast not. > N.B AddressSanitizer will diagnose this at runtime. +1
