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Re: [PATCH] Define CLOCKS_PER_SEC type to the type clock_t
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Paul Eggert <eggert at cs dot ucla dot edu>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 5 Jan 2015 14:51:45 -0800
- Subject: Re: [PATCH] Define CLOCKS_PER_SEC type to the type clock_t
- Authentication-results: sourceware.org; auth=none
- References: <20150105204653 dot GA31001 at intel dot com> <54AB1115 dot 80608 at cs dot ucla dot edu> <CAMe9rOrExjqKKFUkjcN+4SzzouGQ7yyq8RnfWxKmotEaQ6aZRQ at mail dot gmail dot com>
On Mon, Jan 5, 2015 at 2:45 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Mon, Jan 5, 2015 at 2:32 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:
>> On 01/05/2015 12:46 PM, H.J. Lu wrote:
>>>
>>> C99 specifies that CLOCKS_PER_SEC is a constant expression
>>
>>
>> A minor point (mostly for comments): CLOCKS_PER_SEC needn't be a constant
>> expression. Even POSIX doesn't require that: on the contrary, it explicitly
>> warns you that it might not be a constant expression, even though it must
>> evaluate to 1000000.
>>
>>> + * bits/time2.h: New file.
>>> + * sysdeps/unix/sysv/linux/x86/bits/time2.h: Likewise.
>>
>>
>> Wouldn't it be simpler and clearer to replace "# define CLOCKS_PER_SEC
>> 1000000l" with "# define CLOCKS_PER_SEC ((clock_t) 1000000)"? That way, one
>> wouldn't need all these other little files running around.
>
> My copy of C99 has
>
> ---
> CLOCKS_PER_SEC
>
> which expands to a constant expression with type clock_t (described below)
> that is the number per second of the value returned by the clock function.
> ---
>
> Has it been changed?
Yes, it does:
http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_281.htm
I will update my patch.
Thanks.
--
H.J.