Linux 未定义的引用 'shm_open'，已在此处添加 -lrt 标志
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undefined reference 'shm_open', already add -lrt flag here
提问by bxshi
I just have a system crash and reinstall Ubuntu 11.10, and my code produces this strange error.
我刚刚系统崩溃并重新安装了 Ubuntu 11.10，我的代码产生了这个奇怪的错误。
I wrote a simple code sample to test where the problem is:
我写了一个简单的代码示例来测试问题出在哪里：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
int main (void) {
int i;
i = shm_open ("/tmp/shared", O_CREAT | O_EXCL, S_IRUSR | S_IWUSR); printf ("shm_open rc = %d\n", i);
shm_unlink ("/tmp/shared");
return (0);
}
and the compile command is
编译命令是
gcc -lrt test.c -o test
gcc -lrt test.c -o test
The error is:
错误是：
/tmp/ccxVIUiP.o: In function `main':
test.c:(.text+0x21): undefined reference to `shm_open'
test.c:(.text+0x46): undefined reference to `shm_unlink'
collect2: ld returned 1 exit status
I have already added -lrt lib, why does it still not compile?
我已经加了-lrt lib，为什么还是编译不出来？
采纳答案by hmjd
Libraries at the end:
最后的图书馆：
gcc test.c -o test -lrt
gcc test.c -o test -lrt
From GCC Link Options:
从GCC 链接选项：
-llibrary
-l library
Search the library named library when linking.
(The second alternative with the library as a separate argument
is only for POSIX compliance and is not recommended.)
It makes a difference where in the command you write this option;
the linker searches and processes libraries and object files in the
order they are specified.
Thus, `foo.o -lz bar.o' searches library `z' after file foo.o but
before bar.o. If bar.o refers to functions in `z', those functions
may not be loaded.
回答by codaddict
Change the compile line from
将编译行从
gcc -lrt test.c -o test
to
到
gcc test.c -o test -lrt
回答by Coaku
In Expert C programmingPage 108:
<Handy Heuristic>
Where to Put Library Options:Always put the -l library options at the rightmost end of your compilation command line.But it doesn't tell why, so i guess this is somewhat a rule?:)
在Expert C programming第 108 页：
<Handy Heuristic>
Where to Put Library Options:Always put the -l library options at the rightmost end of your compilation command line.但它没有说明原因，所以我想这有点规则？:)
