Question

我想在没有优化的情况下编译我的C代码，但是当我在编译命令中添加-O0选项时，我得到了很多“多个定义”错误，我甚至没有写过函数！我想这里有一些显而易见的东西我在这里不知道但作为一个菜鸟我只是想不出来......

这是我的代码：

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <wiringPi.h>
#include <time.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <semaphore.h>
#include <unistd.h>
#include <sched.h>
#include <time.h>

#define N       1800

unsigned long int tsec, tnsec;

int main(void)
{
        int err, i;
        printf("started\n");

        struct timespec tps, tpe, req, rem;

        req.tv_nsec = 400000;
        req.tv_sec = 0;

        struct sched_param param;
        param.sched_priority = 99;
        err = sched_setscheduler(getpid(), SCHED_FIFO, &param);
        if (err != 0)
                printf("sched_setscheduler error");
        err = sched_getparam(getpid(), &param);
        if (err != 0)
                printf("sched_getparam error");
        printf("priority = %i\n", param.sched_priority);

        int policy = sched_getscheduler(getpid());
        printf("policy = %i\n", policy);


        sleep(1);

        clock_gettime(CLOCK_REALTIME, &tps);

        #include "noppynop2.c"
        #include "noppynop2.c"
        #include "noppynop2.c"
        #include "noppynop2.c"
        #include "noppynop2.c"
        #include "noppynop2.c"


        clock_gettime(CLOCK_REALTIME, &tpe);
        tnsec = tpe.tv_nsec - tps.tv_nsec;
        tsec = tpe.tv_sec - tps.tv_sec;
        printf("time = %lu sec %lu nsec\n", tsec, tnsec);


        printf("finished\n");

        return 0;
}

总而言之，这是在实时内核的Linux上造成延迟的暴力尝试。 “noppynop2.c”包含500次asm（“nop”）。我不认为这是问题，但这是背景。代码主要只是一个测试，我想摆脱所有的优化，因为目前编译器倾向于删除（显然）不可预测的数量的“nops”，这与我正在尝试做的完全相反...

当我在没有-O0选项的情况下进行编译时，一切正常：

pi@raspberrypi ~/Desktop/Projects/test_timemeasure_sched $ gcc -Wall -o test_time_measure_sched main.c -lwiringPi -lpthread -lrt
main.c: In function ‘main’:
main.c:22:33: warning: unused variable ‘rem’ [-Wunused-variable]
main.c:22:28: warning: variable ‘req’ set but not used [-Wunused-but-set-variable]
main.c:19:11: warning: unused variable ‘i’ [-Wunused-variable]

但是当我在这里添加-O0时，我得到的是：

pi@raspberrypi ~/Desktop/Projects/test_timemeasure_sched $ gcc -Wall -o -O0 test_time_measure_sched main.c -lwiringPi -lpthread -lrt
main.c: In function ‘main’:
main.c:22:33: warning: unused variable ‘rem’ [-Wunused-variable]
main.c:22:28: warning: variable ‘req’ set but not used [-Wunused-but-set-variable]
main.c:19:11: warning: unused variable ‘i’ [-Wunused-variable]
test_time_measure_sched: In function `_fini':
:(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crti.o:(.fini+0x0): first defined here
test_time_measure_sched: In function `__data_start':
:(.data+0x0): multiple definition of `__data_start'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o:(.data+0x0): first defined here
test_time_measure_sched: In function `__data_start':
:(.data+0x4): multiple definition of `__dso_handle'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/crtbegin.o:(.data+0x0): first defined here
test_time_measure_sched:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o:(.rodata.cst4+0x0): first defined here
test_time_measure_sched: In function `_start':
:(.text+0x0): multiple definition of `_start'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o:(.text+0x0): first defined here
test_time_measure_sched: In function `_init':
:(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crti.o:(.init+0x0): first defined here
/tmp/cc5At86c.o: In function `main':
main.c:(.text+0x0): multiple definition of `main'
test_time_measure_sched::(.text+0xac): first defined here
collect2: ld returned 1 exit status

我该怎么做才能摆脱这些错误？

Thanx提前为您提供帮助。

最好的问候。

埃里克

Answer 1

gcc命令应该是

gcc -Wall -O0 -o test_time_measure_sched main.c -lwiringPi -lpthread -lrt

而不是

gcc -Wall -o -O0 test_time_measure_sched main.c -lwiringPi -lpthread -lrt

使用第二个命令，旧的二进制test_time_measure_sched被gcc视为输入文件。您获得的其他错误都是链接器错误，这表明gcc尝试将旧二进制文件链接到您的新代码。

海湾合作委员会：与-O0的奇怪错误，没有没有

1 个答案: