我给了-lrt作为编译器的最后一个链接器标志。但是仍然出现此错误。
arif@khost:~/sak/sak.exosip$ gcc eXo_init.c -I/opt/osip2/include -I/opt/exosip/include -L/opt/osip2/lib -L/opt/exosip/lib -leXosip2 -losipparser2 -losip2 -lrt
/opt/osip2/lib/libosip2.so: undefined reference to `clock_gettime'
collect2: ld returned 1 exit status
手册页中说:
NAME
clock_getres, clock_gettime, clock_settime - clock and time functions
SYNOPSIS
#include <time.h>
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.
所以我很困惑我做错了什么。
我试图阅读
librt.so中的符号没有运气:arif@khost:~/sak/ortp/src/tests$ nm /lib/x86_64-linux-gnu/librt-2.15.so
nm: /lib/x86_64-linux-gnu/librt-2.15.so: no symbols
更新1 我无法从
librt.so中读取符号的原因是它们被“剥离”了。我在哪里可以获得符号名称？arif@khost:~/sak/ortp/src/tests$ file /lib/x86_64-linux-gnu/librt-2.15.so
/lib/x86_64-linux-gnu/librt-2.15.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), BuildID[sha1]=0x375b2c35c4e6503a5d1a88ab6f76f5b6e0ee81df, for GNU/Linux 2.6.24, stripped
更新2
好了，事情变得非常困惑，因为以下测试代码可以编译并正常运行:
#include <time.h>
#include <unistd.h>
#include <stdio.h>
int main(int argc, char **argv, char **arge) {
struct timespec tps, tpe;
if ((clock_gettime(CLOCK_REALTIME, &tps) != 0)
|| (clock_gettime(CLOCK_REALTIME, &tpe) != 0)) {
perror("clock_gettime");
return -1;
}
printf("%lu s, %lu ns\n", tpe.tv_sec-tps.tv_sec,tpe.tv_nsec-tps.tv_nsec);
return 0;
}
内置
arif@khost:~/sak/sak.exosip$ gcc what.c -lrt
UPDATE3 我正在尝试编译的代码:
#include <eXosip2/eXosip.h>
#include <netinet/in.h>
#include <unistd.h>
int ex_init(int port)
{
struct eXosip_t *eXcontext;
int i;
TRACE_INITIALIZE(6, stdout);
i = eXosip_init(eXcontext);
if (i != 0)
return -1;
i = eXosip_listen_addr(eXcontext, IPPROTO_UDP, NULL, port, AF_INET, 0);
if (i != 0) {
eXosip_quit(eXcontext);
fprintf (stderr, "could not initialize transport layer\n");
return -1;
}
return 1;
}
int main(int argc, char **argv) {
if(ex_init(1000))
printf("success \n");
return 0;
}
最佳答案
好了，问题解决了，如果我通过了这个链接器标志
-Wl,--no-as-needed
在命令行中的库列表之前。
为什么这样有效，因为在我的平台中，链接器始终与
-Wl,--as-needed一起传递。从
ld手册:--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.
因此，当在库之前给出
--as-needed时，liker仅链接该库的NEEDED部分中给出的库。例如，
-Wl,--as-needed -llibA -llibB -llibC
这是在
libA之前给出的。因此，在链接期间，链接器将检查NEEDED的libA部分。如果在NEEDED的libA部分中仅列出libC，则不会链接libB。发生此特定问题是因为
arif@khost:~/sak/sak.exosip$ objdump -p /opt/osip2/lib/libosip2.so.10 | grep NEEDED
NEEDED libosipparser2.so.10
NEEDED libc.so.6
libosip2不会将librt列为NEEDED。如果我通过
--no-as-needed，那么所有库都将被链接，无论ELF的NEEDED部分中给出的内容如何。尽管不是这种情况，因为，
arif@khost:~/sak/sak.exosip$ nm --demangle /opt/osip2/lib/libosip2.so.10 | grep clock_gettime
U clock_gettime
它具有由
clock_gettime提供的 undefined symbol librt.so。嗯，这实际上是
libosip2开发人员的错误，即他们的autotools无法与--as-needed一起使用。osip使用的链接命令:
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
因此，它未与
librt链接，这就是为什么其未在其librt列表中列出NEEDED的原因如果配置有:
LDFLAGS="${LDFLAGS} -lrt" ./configure --prefix=/opt/osip2-test/
然后，链接命令变为:
libtool: link: gcc -shared -fPIC -DPIC .libs/ict_fsm.o .libs/ist_fsm.o .libs/nict_fsm.o .libs/nist_fsm.o .libs/ict.o .libs/ist.o .libs/nict.o .libs/nist.o .libs/fsm_misc.o .libs/osip.o .libs/osip_transaction.o .libs/osip_event.o .libs/port_fifo.o .libs/osip_dialog.o .libs/osip_time.o .libs/port_sema.o .libs/port_thread.o .libs/port_condv.o -Wl,-rpath -Wl,/home/arif/sak/osip/src/osipparser2/.libs -Wl,-rpath -Wl,/opt/osip2-test/lib -lnsl ../osipparser2/.libs/libosipparser2.so -lrt -Wl,-soname -Wl,libosip2.so.10 -o .libs/libosip2.so.10.0.0
因此，它与
librt链接。它也反射(reflect)在其ELF中:arif@khost:~/sak/osip/src/osip2/.libs$ objdump -p libosip2.so.10 | grep NEEDED
NEEDED libosipparser2.so.10
NEEDED librt.so.1
NEEDED libc.so.6
此补丁可解决此问题:
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
相关usenet讨论线程:
https://groups.google.com/forum/#!topic/comp.unix.programmer/VKbARy6W4AY
更新:
osip开发人员回复了我的邮件。他用不同的补丁修复了这个问题(然后是我的更一般的解决方案)
http://git.savannah.gnu.org/cgit/osip.git/commit/?id=bd5b1ad58381e4bfce08bad9b66ad00cd28f9b65
关于linux - 尽管给出了 `clock_gettime`，但未定义对 `-lrt`的引用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17150075/