[tz] localtime.c issue
apb at cequrux.com
Mon Jul 8 21:49:53 UTC 2013
On Mon, 08 Jul 2013, Paul_Koning at Dell.com wrote:
>> Perhaps this will work without either a compiler warning or potential loss of precision:
>> seconds = tdays * SECSPERDAY + (time_t)0.5;
>> --apb (Alan Barrett)
> I rather doubt it. Casting 0.5 to an integer type (as time_t
> is) ends up adding 0 or 1, but not 0.5.
The whole point of adding 0.5 before converting from time_t to
int_fast32_t is to round up if time_t happens to be a floating
point type, and to do nothing if time_t happens to be an integral
type. You can't assume that time_t is an integral type.
>How about (tdays * SECSPERDAY * 2 + 1) / 2; ?
Multiplying by 2 might overflow the available range. (I have not
checked whether there are reasons why it would always be safe.)
--apb (Alan Barrett)
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