Hello gnulibbers,
I have a curious issue. I would like to use clock_gettime with
CLOCK_PROCESS_CPUTIME_ID. clock_gettime(2) notes some portability
issues with this timer, suggesting that the user call
clock_getcpuclockid(0) to verify that the timer is available.
I was using the clock-time module, but it turns out that on uclibc,
clock_gettime is available in libc, but clock_getcpuclockid is only
available in librt. Thus the clock-time check doesn't add -lrt.
Here's a note from a user. The quoted text is mine.
> Is it perhaps that clock_getcpuclockid is in -lrt but clock_gettime is
> in your libc?
clock_gettime is in both of them:
/lib # readelf -s librt.so.0 | grep clock
42: 00001cb4 68 FUNC GLOBAL DEFAULT 6 clock_gettime
44: 00001a78 172 FUNC GLOBAL DEFAULT 6 clock_nanosleep
64: 00001b74 88 FUNC GLOBAL DEFAULT 6 clock_getcpuclockid
/lib # readelf -s libc.so.0 | grep clock
166: 0000fcf4 72 FUNC GLOBAL DEFAULT 6 clock_gettime
514: 00011868 72 FUNC GLOBAL DEFAULT 6 clock_settime
537: 0000fa84 72 FUNC GLOBAL DEFAULT 6 clock_getres
762: 0002a588 56 FUNC GLOBAL DEFAULT 6 clock
but getcpuclockid is only in librt.
I "solved" this issue with a patch like the attached (to a locally
included gl_CLOCK_TIME). What do you think is the right thing to do
here?
Thanks,
Andy
>From 5ad05b93a3f02be7c66fbab9c49e23ca314b7c33 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wi...@pobox.com>
Date: Fri, 20 May 2011 18:48:33 +0200
Subject: [PATCH] check for clock_getcpuclockid in gl_CLOCK_TIME
* acinclude.m4 (gl_CLOCK_TIME): It could be that clock_gettime is in
libc but clock_getcpuclockid is not, so check for that explicitly.
---
acinclude.m4 | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/acinclude.m4 b/acinclude.m4
index ba8b090..5bd1ced 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -529,8 +529,14 @@ AC_DEFUN([gl_CLOCK_TIME],
AC_SUBST([LIB_CLOCK_GETTIME])
gl_saved_libs=$LIBS
AC_SEARCH_LIBS([clock_gettime], [rt posix4],
- [test "$ac_cv_search_clock_gettime" = "none required" ||
- LIB_CLOCK_GETTIME=$ac_cv_search_clock_gettime])
- AC_CHECK_FUNCS([clock_gettime clock_settime])
+ [if test "$ac_cv_search_clock_gettime" = "none required"; then
+ AC_SEARCH_LIBS([clock_getcpuclockid], [rt posix4],
+ [test "$ac_cv_search_clock_getcpuclockid" = "none required" \
+ || LIB_CLOCK_GETTIME=$ac_cv_search_clock_getcpuclockid],
+ [LIB_CLOCK_GETTIME=$ac_cv_search_clock_gettime])
+ else
+ LIB_CLOCK_GETTIME=$ac_cv_search_clock_gettime
+ fi])
+ AC_CHECK_FUNCS([clock_gettime clock_settime clock_getcpuclockid])
LIBS=$gl_saved_libs
])
--
1.7.5.1
--
http://wingolog.org/
