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. Such an attribute would of course be preserved by e.g. "typedef time_t my_time_t;". It would need composite type rules defined (probably the composite type has the attribute if either of the two types does), and rules for what happens to the attribute in integer promotions / usual arithmetic conversions (I'm guessing that given "time_t x;", it's desired to warn about truncation of x+1, for example, so the process of applying usual arithmetic conversions to determine the type of x+1 should not have lost the attribute; what's less clear is e.g. x+1LL if time_t is narrower than long long). -- Joseph S. Myers josmy...@redhat.com
