未定义的引用另一个库中的函数 [英] Undefined reference to a function in another library
问题描述
我试图编译一个引用了一个lib的对象代码。这是libexample.c的代码:
#includelibexample.h
#include< signal。 h取代;
#include< time.h>
timer_t sched;
struct itimerspec timer = {{0,0},{0,0}};
void init(){
struct sigaction sa;
sigemptyset(& sa.sa_mask);
sigaction(SIGALRM,& sa,NULL);
timer_create(CLOCK_PROCESS_CPUTIME_ID,NULL,& sched);
timer_settime(sched,TIMER_ABSTIME,& timer,NULL);
}
以及示例程序的简单代码:
#includelibexample.h
int main(){
init();
返回0;
}
我使用它来编译:
gcc libexample.c -c -lrt -o libexample.o
gcc example.c -lrt ibexample.o -o示例
当我尝试使用第二行进行编译时,我得到了这个结果:
./ libexample.so:对`timer_create'的未定义引用
./libexample.so:对`timer_settime'的未定义引用
任何人都知道我在做什么错了?
解决方案
man timer_create 命令解释你:
名称
timer_create - 创建一个POSIX每进程计时器
概要
#include< signal.h>
#include< time.h>
int timer_create(clockid_t clockid,struct sigevent * sevp,
timer_t * timerid);
与-lrt链接。
所以你应该像文档所说的那样链接
-lrt
因此,使用
gcc libexample.c -fPIC -shared -o libexample.so -lrt
生成您的
libexample .so
。
由于 undur_gongor 注释,你需要在所有剩下的部分(通常顺序为
gcc
参数是源文件,目标文件,依赖顺序的库)在gcc
或ld
命令中(并且记录在ld
文档,并在gcc
ones)。所以-lrt
应该放在最后。
并学会阅读手册页。
I'm trying to compile an object code with a reference to one lib. This is the code of libexample.c:
#include "libexample.h" #include <signal.h> #include <time.h> timer_t sched; struct itimerspec timer = {{0, 0}, {0, 0}}; void init() { struct sigaction sa; sigemptyset(&sa.sa_mask); sigaction(SIGALRM, &sa, NULL); timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &sched); timer_settime(sched, TIMER_ABSTIME, &timer, NULL); }
And the simple code of a example program:
#include "libexample.h" int main() { init(); return 0; }
I use this to compile:
gcc libexample.c -c -lrt -o libexample.o gcc example.c -lrt ibexample.o -o example
And I get this when I'm trying to compile with the second line:
./libexample.so: undefined reference to `timer_create' ./libexample.so: undefined reference to `timer_settime'
Anyone knows what I'm doing wrong?
解决方案The
man timer_create
command explains you:NAME timer_create - create a POSIX per-process timer SYNOPSIS #include <signal.h> #include <time.h> int timer_create(clockid_t clockid, struct sigevent *sevp, timer_t *timerid); Link with -lrt.
So you should, as documentation says, link with
-lrt
.So use
gcc libexample.c -fPIC -shared -o libexample.so -lrt
to produce your
libexample.so
.As undur_gongor commented, you need to put the libraries in good order after all the rest (the usual order for
gcc
arguments is source files, object files, libraries in dependency order) ingcc
orld
commands (and that is documented inld
documentation, and ingcc
ones). So-lrt
should go last.And learn to read man pages.
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