[tz] localtime.c issue
Andy Heninger
aheninger at google.com
Mon Jul 8 22:00:45 UTC 2013
Whatever the code ends up being, it would be helpful if it produced no
compiler warnings with the warning level cranked up to the maximum, on
either gcc or clang.
-- Andy
On Mon, Jul 8, 2013 at 2:49 PM, Alan Barrett <apb at cequrux.com> wrote:
> 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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