diff mbox

Define CLOCKS_PER_SEC type to the type clock_t

Message ID CAMe9rOrpk5vHFjL=EFNByhwBSj34zYFc7+YyfyCUt8JJjD0idw@mail.gmail.com
State Superseded
Headers show

Commit Message

H.J. Lu Jan. 6, 2015, 1:06 a.m. UTC
On Mon, Jan 5, 2015 at 3:43 PM, Paul Eggert <eggert@cs.ucla.edu> wrote:
> On 01/05/2015 03:25 PM, H.J. Lu wrote:
>>
>> This is the updated patch.  OK to install?
>
>
> Looks good to me, and thanks.

Well, it doesn't work due to:

#if CLOCKS_PER_SEC != 1000000l
# error "CLOCKS_PER_SEC should be 1000000"
#endif

in sysdeps/unix/sysv/linux/clock.c.

Here is the updated patch.  I replaced the above # error with

 assert (CLOCKS_PER_SEC == 1000000l);

I compared the assembly outputs before and after.  There
are no differences on i686 and x86-64.  OK to install?

Thanks.

Comments

Paul Eggert Jan. 6, 2015, 4:47 a.m. UTC | #1
H.J. Lu wrote:
> assert (CLOCKS_PER_SEC == 1000000l);

This fails only at runtime if the value is wrong, which is not as good as 
checking it at compile-time.  Something like this, perhaps:

#if __STDC_VERSION__ < 201112L
# define _Static_assert(e, s) extern int (*static_assert_checker (void)) \
     [sizeof (struct { unsigned int error_if_negative: (e) ? 1 : -1; })]
#endif
#define verify(e) _Static_assert (e, "verify (" #e ")")

and then use 'verify' instead of 'assert'.

Also, there's no need for the trailing 'l' here.
Andreas Schwab Jan. 6, 2015, 2:22 p.m. UTC | #2
Paul Eggert <eggert@cs.ucla.edu> writes:

> H.J. Lu wrote:
>> assert (CLOCKS_PER_SEC == 1000000l);
>
> This fails only at runtime if the value is wrong, which is not as good as
> checking it at compile-time.

Does it matter?

Andreas.
Paul Eggert Jan. 6, 2015, 3:57 p.m. UTC | #3
On 01/06/2015 06:22 AM, Andreas Schwab wrote:
>> This fails only at runtime if the value is wrong, which is not as good as
>> >checking it at compile-time.
> Does it matter?

Not so much here, no, since the constant is always 1 million and the 
assert is optimized away.  Still, we should prefer compile-time checking.
diff mbox

Patch

From ef3088c8da5288533cd9197e928b33bdc8833718 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 5 Jan 2015 11:47:31 -0800
Subject: [PATCH] Define CLOCKS_PER_SEC type to the type clock_t

C99 specifies that CLOCKS_PER_SEC is an expression with the type clock_t.
This patch adds a generic <bits/time2.h> to define CLOCKS_PER_SEC and
provides the Linux/x86-64 version of <bits/time2.h> to support x32.

	[BZ #17797]
	* bits/time.h (CLOCKS_PER_SEC): Changed to ((clock_t) 1000000).
	* sysdeps/unix/sysv/linux/bits/time.h (CLOCKS_PER_SEC): Likewise.
	* sysdeps/unix/sysv/linux/clock.c: Include <assert.h>.
	(clock): Assert CLOCKS_PER_SEC == 1000000l.
	* time/clocktest.c (main): Replace %ld with %jd and cast to
	intmax_t.
---
 ChangeLog                           | 10 ++++++++++
 NEWS                                |  2 +-
 bits/time.h                         |  8 ++++----
 sysdeps/unix/sysv/linux/bits/time.h |  8 ++++----
 sysdeps/unix/sysv/linux/clock.c     |  7 +++----
 time/clocktest.c                    |  4 ++--
 6 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 262e300..7d34cc6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@ 
+2015-01-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	[BZ #17797]
+	* bits/time.h (CLOCKS_PER_SEC): Changed to ((clock_t) 1000000).
+	* sysdeps/unix/sysv/linux/bits/time.h (CLOCKS_PER_SEC): Likewise.
+	* sysdeps/unix/sysv/linux/clock.c: Include <assert.h>.
+	(clock): Assert CLOCKS_PER_SEC == 1000000l.
+	* time/clocktest.c (main): Replace %ld with %jd and cast to
+	intmax_t.
+
 2015-01-05  Roland McGrath  <roland@hack.frob.com>
 
 	* sysdeps/generic/unwind-resume.h: New file.
diff --git a/NEWS b/NEWS
index 63918df..49c0a2d 100644
--- a/NEWS
+++ b/NEWS
@@ -16,7 +16,7 @@  Version 2.21
   17583, 17584, 17585, 17589, 17594, 17601, 17608, 17616, 17625, 17630,
   17633, 17634, 17635, 17647, 17653, 17657, 17664, 17665, 17668, 17682,
   17717, 17719, 17722, 17723, 17724, 17725, 17732, 17733, 17744, 17745,
-  17746, 17747, 17775, 17777, 17780, 17781, 17782, 17793, 17796
+  17746, 17747, 17775, 17777, 17780, 17781, 17782, 17793, 17796, 17797
 
 * i386 memcpy functions optimized with SSE2 unaligned load/store.
 
diff --git a/bits/time.h b/bits/time.h
index ae17b7f..7585ddf 100644
--- a/bits/time.h
+++ b/bits/time.h
@@ -24,13 +24,13 @@ 
 # ifndef _BITS_TIME_H
 #  define _BITS_TIME_H	1
 
-/* ISO/IEC 9899:1990 7.12.1: <time.h>
-   The macro `CLOCKS_PER_SEC' is the number per second of the value
-   returned by the `clock' function. */
+/* ISO/IEC 9899:1999 7.23.1: Components of time
+   The macro `CLOCKS_PER_SEC' is an expression with type `clock_t' that is
+   the number per second of the value returned by the `clock' function.  */
 /* CAE XSH, Issue 4, Version 2: <time.h>
    The value of CLOCKS_PER_SEC is required to be 1 million on all
    XSI-conformant systems. */
-#  define CLOCKS_PER_SEC  1000000l
+#  define CLOCKS_PER_SEC  ((clock_t) 1000000)
 
 #  if !defined __STRICT_ANSI__ && !defined __USE_XOPEN2K
 /* Even though CLOCKS_PER_SEC has such a strange value CLK_TCK
diff --git a/sysdeps/unix/sysv/linux/bits/time.h b/sysdeps/unix/sysv/linux/bits/time.h
index 226d6dd..706946c 100644
--- a/sysdeps/unix/sysv/linux/bits/time.h
+++ b/sysdeps/unix/sysv/linux/bits/time.h
@@ -39,13 +39,13 @@  struct timeval
 # ifndef _BITS_TIME_H
 #  define _BITS_TIME_H	1
 
-/* ISO/IEC 9899:1990 7.12.1: <time.h>
-   The macro `CLOCKS_PER_SEC' is the number per second of the value
-   returned by the `clock' function. */
+/* ISO/IEC 9899:1999 7.23.1: Components of time
+   The macro `CLOCKS_PER_SEC' is an expression with type `clock_t' that is
+   the number per second of the value returned by the `clock' function.  */
 /* CAE XSH, Issue 4, Version 2: <time.h>
    The value of CLOCKS_PER_SEC is required to be 1 million on all
    XSI-conformant systems. */
-#  define CLOCKS_PER_SEC  1000000l
+#  define CLOCKS_PER_SEC  ((clock_t) 1000000)
 
 #  if (!defined __STRICT_ANSI__ || defined __USE_POSIX) \
    && !defined __USE_XOPEN2K
diff --git a/sysdeps/unix/sysv/linux/clock.c b/sysdeps/unix/sysv/linux/clock.c
index e06c4b3..b76ad77 100644
--- a/sysdeps/unix/sysv/linux/clock.c
+++ b/sysdeps/unix/sysv/linux/clock.c
@@ -19,16 +19,15 @@ 
 #include <sys/times.h>
 #include <time.h>
 #include <unistd.h>
-
-#if CLOCKS_PER_SEC != 1000000l
-# error "CLOCKS_PER_SEC should be 1000000"
-#endif
+#include <assert.h>
 
 clock_t
 clock (void)
 {
   struct timespec ts;
 
+  assert (CLOCKS_PER_SEC == 1000000l);
+
   /* clock_gettime shouldn't fail here since CLOCK_PROCESS_CPUTIME_ID is
      supported since 2.6.12.  Check the return value anyway in case the kernel
      barfs on us for some reason.  */
diff --git a/time/clocktest.c b/time/clocktest.c
index 2e6457d..13b7420 100644
--- a/time/clocktest.c
+++ b/time/clocktest.c
@@ -30,7 +30,7 @@  main (int argc, char ** argv)
 
   printf ("%jd clock ticks per second (start=%jd,stop=%jd)\n",
 	  (intmax_t) (stop - start), (intmax_t) start, (intmax_t) stop);
-  printf ("CLOCKS_PER_SEC=%ld, sysconf(_SC_CLK_TCK)=%ld\n",
-	  CLOCKS_PER_SEC, sysconf(_SC_CLK_TCK));
+  printf ("CLOCKS_PER_SEC=%jd, sysconf(_SC_CLK_TCK)=%ld\n",
+	  (intmax_t) CLOCKS_PER_SEC, sysconf(_SC_CLK_TCK));
   return 0;
 }
-- 
1.9.3