do_gettimeofday()undefined reference

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Le Sunday 04 October 2009 à 00:22:41, vous avez écrit :
> Hello:
> I am new to linux and facing a simple compile problem. I have written a C
> file which is using the do_gettimeofday() function.
>
> #include <linux/time.h>
> #include <stdio.h>
>
> main()
> {
>    struct timeval start;
>
>    do_gettimeofday(&start);
>    printf ("%d", start.tv_usec);
> }
>
> gcc a1.c --
>  undefined reference to `do_gettimeofday'
>
>
> here is the PATH:
>
> echo $PATH
> /usr/lib/qt-3.3/bin:/usr/kerberos/bin:/usr/lib/ccache:/usr/local/bin:/bin:/
>usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/homes/iws/arpalla/bin
>
> I checked that the /usr/include/linux/time.h file got the function
> declaration for do_gettimeofday()
>
> Is there anything missing in the PATH variable?
>
> I am facing same error for rdtscl() function as well!!
>
> The Linux version is :
>
> [arpalla]$ uname -a
> Linux <..> 2.6.30-2.0 #6 SMP Mon Sep 21 11:03:44 PDT 2009 i686 i686 i386
> GNU/Linux
>
> Can anyone please help?
>
> Thanks,
> Anu

% man gettimeofday
NAME
 gettimeofday, settimeofday - get / set time

SYNOPSIS
#include <sys/time.h>

int gettimeofday(struct timeval *tv, struct timezone *tz);
int settimeofday(const struct timeval *tvtz);

DESCRIPTION
 The functions gettimeofday() and settimeofday() can get and set the time as 
well as a timezone. The tv argument is a struct timeval (as specified in
<sys/time.h>): 

struct timeval {
    time_t      tv_sec;     /* seconds */
    suseconds_t tv_usec;    /* microseconds */
};
[...]


// getsecond.c
#include <sys/time.h>
#include <stdio.h>

main(void) {

    struct timeval tv;
    double t = 0.0;

    if ( gettimeofday(&tv, NULL) != -1 )
        t = tv.tv_usec / 1000000.0 + tv.tv_sec;

    printf ("%f\n", t);
}

% gcc -O2 -s getsecond.c -o getsecond.bin

% ./getsecond.bin
1254613660.603762

+@

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