Undefined reference to `clock_gettime` although `-lrt` is given
Well the problem is solved If i pass this linker flag
-Wl,--no-as-needed
Before the library list in command line.
Why this works because in my platform, linker is always passed with -Wl,--as-needed
.
From ld
manual :
--as-needed
--no-as-needed
This option affects ELF DT_NEEDED tags for dynamic libraries
mentioned on the command line after the --as-needed option.
Normally the linker will add a DT_NEEDED tag for each dynamic
library mentioned on the command line, regardless of whether the
library is actually needed or not. --as-needed causes a DT_NEEDED
tag to only be emitted for a library that satisfies an undefined
symbol reference from a regular object file or, if the library is
not found in the DT_NEEDED lists of other libraries linked up to
that point, an undefined symbol reference from another dynamic
library. --no-as-needed restores the default behaviour.
So when --as-needed
is given before a library , liker only links with the libraries which are given in NEEDED
section of the library.
For example,
-Wl,--as-needed -llibA -llibB -llibC
Here --as-needed is given before libA
. So during linking, linker will examine the NEEDED
section of libA
. If in NEEDED
section of libA
lists only libC
, then the libB
will not be linked.
This specific problem occurred because
arif@khost:~/sak/sak.exosip$ objdump -p /opt/osip2/lib/libosip2.so.10 | grep NEEDED
NEEDED libosipparser2.so.10
NEEDED libc.so.6
libosip2
does not lists librt
as NEEDED
.
If i pass --no-as-needed
, then all the libraries will be linked regardless of what is given in ELF's NEEDED
section.
Although this should not be the case because,
arif@khost:~/sak/sak.exosip$ nm --demangle /opt/osip2/lib/libosip2.so.10 | grep clock_gettime
U clock_gettime
It has undefined symbol clock_gettime
which is provided by librt.so
.
Well its actually a fault of the libosip2
devs that their autotools
is not working with --as-needed
.
The link command used by osip:
libtool: link: gcc -shared -fPIC -DPIC .libs/ict_fsm.o .libs/ist_fsm.o .libs/nict_fsm.o .libs/nist_fsm.o .libs/ict.o .libs/ist.o .libs/nict.o .libs/nist.o .libs/fsm_misc.o .libs/osip.o .libs/osip_transaction.o .libs/osip_event.o .libs/port_fifo.o .libs/osip_dialog.o .libs/osip_time.o .libs/port_sema.o .libs/port_thread.o .libs/port_condv.o -Wl,-rpath -Wl,/home/arif/sak/osip/src/osipparser2/.libs -Wl,-rpath -Wl,/opt/osip2-test/lib -lnsl ../osipparser2/.libs/libosipparser2.so -Wl,-soname -Wl,libosip2.so.10 -o .libs/libosip2.so.10.0.0
So its not linking with librt
and thats why its not listing librt
in its NEEDED
list
If configured with :
LDFLAGS="${LDFLAGS} -lrt" ./configure --prefix=/opt/osip2-test/
Then the link command becomes :
libtool: link: gcc -shared -fPIC -DPIC .libs/ict_fsm.o .libs/ist_fsm.o .libs/nict_fsm.o .libs/nist_fsm.o .libs/ict.o .libs/ist.o .libs/nict.o .libs/nist.o .libs/fsm_misc.o .libs/osip.o .libs/osip_transaction.o .libs/osip_event.o .libs/port_fifo.o .libs/osip_dialog.o .libs/osip_time.o .libs/port_sema.o .libs/port_thread.o .libs/port_condv.o -Wl,-rpath -Wl,/home/arif/sak/osip/src/osipparser2/.libs -Wl,-rpath -Wl,/opt/osip2-test/lib -lnsl ../osipparser2/.libs/libosipparser2.so -lrt -Wl,-soname -Wl,libosip2.so.10 -o .libs/libosip2.so.10.0.0
So its linking with librt
. Its also reflected in its ELF:
arif@khost:~/sak/osip/src/osip2/.libs$ objdump -p libosip2.so.10 | grep NEEDED
NEEDED libosipparser2.so.10
NEEDED librt.so.1
NEEDED libc.so.6
This patch fixes this :
diff --git a/src/osip2/Makefile.am b/src/osip2/Makefile.am
index bb0d8f3..b72c22a 100644
--- a/src/osip2/Makefile.am
+++ b/src/osip2/Makefile.am
@@ -14,7 +14,7 @@ libosip2_la_SOURCES+=port_sema.c port_thread.c port_condv.c
endif
libosip2_la_LDFLAGS = -version-info $(LIBOSIP_SO_VERSION) \
- $(FSM_LIB) $(EXTRA_LIB) ../osipparser2/libosipparser2.la -no-undefined
+ $(FSM_LIB) $(EXTRA_LIB) ../osipparser2/libosipparser2.la -no-undefined -lrt
INCLUDES = -I$(top_srcdir)/includ
Relevant usenet discussion thread :
https://groups.google.com/forum/#!topic/comp.unix.programmer/VKbARy6W4AY
UPDATE:
osip developer responded to my mail. He fixed it with a different patch (More general solution then mine)
http://git.savannah.gnu.org/cgit/osip.git/commit/?id=bd5b1ad58381e4bfce08bad9b66ad00cd28f9b65
C++ error: undefined reference to 'clock_gettime' and 'clock_settime'
Add -lrt
to the end of g++ command line. This links in the librt.so "Real Time" shared library.
Undefined reference to clock_gettime, gcc 4.6 & cmake
You should ensure that -lpthread -lrt
appear after your libraries like ../lib/libLibUtil.a
Getting undefined reference to 'clock_gettime' error, for curl program
Try linking with librt (-lrt
).
undefined reference to `clock_gettime' . Adding LIBRTDEF=-lrt to Makefile does not fix it
You have included a piece from the main Makefile and not from the makefile in the directory called centrality that does the compiling.
Try this:
cd centrality
g++ -o centrality centrality.cpp Snap.o -I../../glib -I../../snap -lrt
and if that works, add the LDFLAGS in this makefile to the centrality/Makefile
Undefined reference to clock_gettime() in Linux using ICC
It looks like you haven't linked librt.a
at all since the linker is ignoring -l
. Perhaps you were supposed to use -lrt
and optionally give the path via -L
.
icpc -lrt -L/usr/lib/x86_64-linux-gnu -o "test" ./src/test.o
Notice I have no spaces between the -l
and its parameter. I also have listed "librt.a" as merely rt
; the linker will add the rest on its own.
Undefined reference to `clock_gettime', modify makefile?
ipopt i see is configured with configure script, reading help from that script i guess you can just ADD_CFLAGS compiler flags:
ADD_CFLAGS=-lrt ./configure
and then run make.
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