On Fri, 27 Jun 2025, Florian Weimer wrote: > * Joseph Myers: > > > On Thu, 26 Jun 2025, Richard Biener wrote: > > > >> The following prototypes diagnostics for conversions to/from time_t > >> where the source/destination does not have sufficient precision for it. > >> I've lumped this into -Wconversion for the moment and didn't bother > >> fixing up the testcase for !ilp32 or the -Wconversion diagnostics that > >> happen. > >> > >> Would -Wtime-conversion (or -Wtime_t-conversion?) be an appropriate > >> option? I'd enable it with -Wconversion. > > > > I think such a warning should be based on an attribute on the time_t type > > that means "warn for implicit truncation of this type" (I'm less clear on > > why warnings for implicit widening conversions *to* time_t are supposed to > > be useful), rather than hardcoding it to be based on the time_t name. > > It's hardly just time_t for which a warning about such implicit truncation > > might be useful. > > Ideally, we'd also warn about conversion to long, when long isn't > actually uint64_t. This way, we can diagnose potential truncation > during 64-bit builds.
Yeah, though fun fact - time_t is 'long' on most 64bit systems ... so you'd diagnose a conversion from long to long. I'm not sure how to make this work generally with the attribute idea when not keying explicitly on 'time_t'. Richard.
