Bug#201664: marked as done (libc: bug in ftime)
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and subject line libc: bug in ftime
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From: ottavio@campana.vi.it
Subject: libc: bug in ftime
To: submit@bugs.debian.org
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Package: libc
Version: N/A
Severity: normal
I've found a bug in libc using ftime. Give a look at this little code:
#include <sys/timeb.h>
#include <unistd.h>
#include <stdio.h>
struct timeb tp;
float old_time = 0;
float new_time = 0;
#define PERFOMANCES ftime(&tp); \
new_time = tp.time + tp.millitm/1000; \
fprintf (stdout, "new: %f\n", new_time); \
fprintf (stdout, "Performances: delta=%f \n", \
new_time-old_time ); \
old_time = new_time;
int main (void) {
while (1) {
usleep (500000);
PERFOMANCES
}
}
Compiling and running it gives you:
bott@dirac:~ > ./test
new: 1058422400.000000
Performances: delta=1058422400.000000
new: 1058422400.000000
Performances: delta=0.000000
new: 1058422400.000000
Performances: delta=0.000000
new: 1058422400.000000
Performances: delta=0.000000
new: 1058422400.000000
Performances: delta=0.000000
new: 1058422400.000000
Performances: delta=0.000000
new: 1058422400.000000
Performances: delta=0.000000
It seems that time gets updated only the first time.
If you need to contact me my email is ottavio@campana.vi.it
-- System Information
Debian Release: 3.0
Kernel Version: Linux dirac 2.4.21-dirac #1 SMP lun giu 23 08:07:23 CEST 2003 i686 unknown
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Received: (at 201664-done) by bugs.debian.org; 8 Oct 2004 03:16:01 +0000
>From gotom@debian.or.jp Thu Oct 07 20:16:01 2004
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Date: Fri, 08 Oct 2004 12:16:01 +0900
Message-ID: <818yahx5la.wl@omega.webmasters.gr.jp>
From: GOTO Masanori <gotom@debian.or.jp>
To: 201664-done@bugs.debian.org,
Francesco Paolo Lovergine <frankie@debian.org>, ottavio@campana.vi.it
Subject: Re: libc: bug in ftime
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> I've found a bug in libc using ftime. Give a look at this little code:
>
(snip)
> #define PERFOMANCES ftime(&tp); \
> new_time = tp.time + tp.millitm/1000; \
> fprintf (stdout, "new: %f\n", new_time); \
> fprintf (stdout, "Performances: delta=%f \n", \
> new_time-old_time ); \
> old_time = new_time;
This code is broken. "millitm" is milli second resolution, so
tp.millitm/1000 is always 0.
> reassign 201664 libc6
> thanks
>
> ftime() is obsolete and buggy in many releases of libc. See its current
> manpage also. These days millitm could be broken again.
Wrong, ftime() works fine.
I close this bug because it's bogus.
Regards,
-- gotom
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