Re: building something with nanotime

["Jim Stapleton" <stapleton dot 41 at gmail dot com>]

Thanks, I wasn't too familiar with that stuff, guess I should have
been more suspicious of the (9) in the man page entry.

although not likely, the code may cross a day threshold, and
gettimeofday could be problematic. What is the simplest way to get a
time interval on something that may cross a day threshold (in ms or
preferrably ns?). I know clock() can get me ticks, but it'll take work
to conver that to second (any simple way to do that)? I understand
clock is for the given thread, and not absolute time, but both may be
relevant at some point.

Thank you,
-Jim Stapleton

On 8/31/07, Brian Dessent <brian@dessent.net> wrote:
> Jim Stapleton wrote:
>
> > FreeBSD
> > ========================================
> > [sjss@elrond ~/dev/numbench]$ gcc numbench.c
> > /var/tmp//ccnZ4l7C.o(.text+0x155c): In function `loop_calibrate':
> > : undefined reference to `nanotime'
> > /var/tmp//ccnZ4l7C.o(.text+0x15b6): In function `loop_calibrate':
> > : undefined reference to `nanotime'
> > /var/tmp//ccnZ4l7C.o(.text+0x15ec): In function `iterbenchI':
> > : undefined reference to `nanotime'
> > /var/tmp//ccnZ4l7C.o(.text+0x165d): In function `iterbenchI':
> > : undefined reference to `nanotime'
> > /var/tmp//ccnZ4l7C.o(.text+0x1694): In function `iterbenchF':
> > : undefined reference to `nanotime'
> > /var/tmp//ccnZ4l7C.o(.text+0x1705): more undefined references to
> > `nanotime' follow
> > ========================================
>
> On FreeBSD this is a kernel mode interface, not available to userspace.
> That is why the manpage is in section 9.  So you can't call this
> function from a normal program.
>
> > Cygwin:
> > ========================================
> > $ gcc numbench.c -lc -lm
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x2b4):
> > undefined reference to `_srandomdev'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x13ef):
> > undefined reference to `_nanotime'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x1445):
> > undefined reference to `_nanotime'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x1478):
> > undefined reference to `_nanotime'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x14e5):
> > undefined reference to `_nanotime'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x1518):
> > undefined reference to `_nanotime'
> > /cygdrive/c/DOCUME~1/STAPLE~1/LOCALS~1/Temp/ccSqoE54.o:numbench.c:(.text+0x1585):
> > more undefined references to `_nanotime' follow
> > collect2: ld returned 1 exit status
> > ========================================
>
> Cygwin does not provide the nanotime function.
>
> > I tried adding a few libraries that might be useful:  -lc -lm -lmd
> > -lpthread, but with no luck. I figured I'd try to find what library it
> > is in, but couldn't (strings /lib/* | grep nano; string /usr/lib/* |
> > grep nano). I could only find nanosleep, and a few other non-nanotime
> > references.
>
> The problem is that you're expecting to be able to use a nonstandard
> function where it does not exist.  I think you need to switch APIs if
> you want to build your code on these platforms.  gettimeofday(2) should
> give you microsecond resolution and is POSIX standard.
>
> Brian
>