From: already5chosen@yahoo.com
On Mon, 5 Jan 2026 16:23:09 -0000 (UTC)
Lew Pitcher wrote:
> On Mon, 05 Jan 2026 10:51:38 +0200, Michael S wrote:
>
> > On Mon, 5 Jan 2026 00:17:07 -0800
> > Andrey Tarasevich wrote:
> >
> >> On Sun 1/4/2026 11:19 PM, Kenny McCormack wrote:
> >> > The question is: How can you reliably printf() a time_t value?
> >> > What conversion spec should you use?
> >>
> >> You can't. As far as the language is concerned, `time_t` is
> >> intended to be an opaque type. It has to be a real type, so it is
> >> either an integer of a plain floating-point type. But other than
> >> that nothing is known about it. There's really no point in
> >> printing it.
> >>
> >> If you still want to, you can do it in some implementation-specific
> >> way. Which still immediately means that you can't do it "reliably",
> >> if I understand what you mean correctly.
> >>
> >
> > I can't think about situation in which casting time_t value to 'long
> > long' can go wrong.
>
> As Andrey pointed out, time_t can resolve to a floatingpoint type,
> so, "long long" would go wrong if the implementation typedefs it to
> float, or
> double, or
> long double.
>
Reading literally what you wrote makes no sense, so I assume that you
meant that 'it' above constitutes time_t rather than 'long long'.
The rest of the post assumes 64-bit 'long long'.
'typedef float time_t' where float==IEEE binary32 is a bad idea, because
you lose your 1sec resolution after 7 months. I.e. with Unix epoch you
lost it a year or two before Ritchi finished his first C compiler.
'typedef double time_t' means that you lost 1 sec resolution ~3
orders of magnitude before you got a chance to overflow 'long long'.
Only in case of 'typedef long double time_t' there is a chance that
overflow happens before resolution is lost. But barely so for 80-bit
long double format prevalent on i386/AMD64 computers.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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