Red Hat Bugzilla – Bug 734836
realtime clock functions need to link with -lrt
Last modified: 2011-12-06 06:48:36 EST
Description of problem:
The clock_gettime(2), clock_settime(2), clock_getres(2) and clock_nanosleep(2) man pages do not mention the fact that you must link to the librt library (with -lrt command line option) to use them.
Without -lrt, the compile fails:
$ gcc test.c
/tmp/ccyoU0Vi.o: In function `getustime':
test.c:(.text+0x36): undefined reference to `clock_gettime'
collect2: ld returned 1 exit status
The latest version of the man page in Fedora 15 does note this fact in the SYNOPSYS section:
int clock_getres(clockid_t clk_id, struct timespec *res);
int clock_gettime(clockid_t clk_id, struct timespec *tp);
int clock_settime(clockid_t clk_id, const struct timespec *tp);
Link with -lrt.
Please update the realtime clock function man pages to note the linking options.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. man clock_gettime
no mention of -lrt link option
note on linking with -lrt
There's something strange with the RHEL 6 man pages: the upstream man-pages-3.22.tar.gz contains the linking notes and was written in 2009, but the RHEL 6 version of the man page is from 2004.
The RHEL 6 man-pages-3.22-17.el6.src.rpm contains a man-pages_syscalls-01.tar.bz2 which overrides a number of the man pages including the clock_* pages with much older versions of the pages.
Is this intentional?
man-pages_syscalls-01.tar.bz2 is from old BZ #159225, when not all man pages was included in upstream tarball. It should be revised and irrelevant man pages removed.
For now, I'll fix four clock_* functions in MPO process in RHEL-6.2, rest when man-pages component will be updated in RHEL.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
Prior to this update, the clock_gettime(2), clock_getres(2), and clock_nanosleep(2) manual pages did not mention the "-lrt" option. With this update, the "-lrt" option is now described in the aforementioned manual pages.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.