4

我正在尝试让代码（见下文）在 Ubuntu 上运行。该代码使用clock_gettime(). 我想我已经成功链接到 librt.a：

**** Build of configuration Debug for project test ****

make -k all 
Building file: ../src/test.cpp
Invoking: Intel Intel(R) 64 C++ Compiler 
icpc -g -I/usr/include/boost -std=c++0x -MMD -MP -MF"src/test.d" -MT"src/test.d" -c -o "src/test.o" "../src/test.cpp"
Finished building: ../src/test.cpp

Building target: test
Invoking: Intel Intel(R) 64 C++ Linker
icpc  -l  /usr/lib/x86_64-linux-gnu/librt.a  -o "test"  ./src/test.o   
icpc: command line warning #10155: ignoring option '-l'; argument required
./src/test.o: In function `main':
/home/p/workspace/test/Debug/../src/test.cpp:12: undefined reference to `clock_gettime'
/home/p/workspace/test/Debug/../src/test.cpp:15: undefined reference to `clock_gettime'
make: *** [test] Error 1
make: Target `all' not remade because of errors.

**** Build Finished ****

但是，我仍然收到有关未定义引用clock_gettime 的错误。这是我的代码：

#include <iostream>
#include <time.h>
using namespace std;

timespec diff(timespec start, timespec end);

int main()
{
    timespec time1, time2;
    int temp;
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);
    for (int i = 0; i< 242000000; i++)
        temp+=temp;
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2);
    cout<<diff(time1,time2).tv_sec<<":"<<diff(time1,time2).tv_nsec<<endl;
    return 0;
}

timespec diff(timespec start, timespec end)
{
    timespec temp;
    if ((end.tv_nsec-start.tv_nsec)<0) {
        temp.tv_sec = end.tv_sec-start.tv_sec-1;
        temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
    } else {
        temp.tv_sec = end.tv_sec-start.tv_sec;
        temp.tv_nsec = end.tv_nsec-start.tv_nsec;
    }
    return temp;
}

有人可以帮忙吗？

4

2 回答 2

9

看起来您根本没有链接librt.a，因为链接器正在忽略-l. 也许您应该使用-lrt并可选择通过-L.

icpc  -lrt -L/usr/lib/x86_64-linux-gnu -o "test"  ./src/test.o

-l注意我和它的参数之间没有空格。我也仅将“librt.a”列为rt；链接器将自行添加其余部分。

于 2013-06-15T23:14:56.273 回答
0

Besides adding -lrt to the linker flags, it's strongly recommended to add -Wl, -no-as-needed to the linker flags as well. Ref from man ld:

--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 ther libraries linked up to that point, an undefined symbol reference from another dynamic library. --no-as-needed restores the default behaviour.

于 2014-01-01T12:47:25.697 回答