This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug libc/13080] clock() is unusable on 32-bit targets due to wrong type for clock_t


http://sourceware.org/bugzilla/show_bug.cgi?id=13080

Rich Felker <bugdal at aerifal dot cx> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|WONTFIX                     |

--- Comment #6 from Rich Felker <bugdal at aerifal dot cx> 2013-05-01 22:01:59 UTC ---
C99 specified for the clock() function:

"If the processor time used is not available or its value cannot be
represented, the function returns the value (clock_t)(-1).275)

Footnotes

275) In order to measure the time spent in a program, the clock function should
be called at the start of the program and its return value subtracted from the
value returned by subsequent calls."

I read the footnote as implying that, except in the case where (clock_t)-1 has
been returned, programs can rely on well-defined behavior if they subtract the
return values of two different invocations of clock(). Moreover, I believe
returning a negative value other than (clock_t)-1 (which will only be negative
if clock_t is a signed type) is non-conforming. If clock_t is to remain signed,
then the clock() function should detect overflow and return -1 once overflow
has occurred. Since CLOCKS_PER_SEC is required by SUS to be 1000000, overflow
will occur very quickly on 32-bit systems, making the clock() function
essentially useless...

-- 
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]