[Bug libc/1952] time() returns incorrect value when given bad address

["michael dot kerrisk at gmx dot net" <sourceware-bugzilla@sourceware.org>]

------- Additional Comments From michael dot kerrisk at gmx dot net  2005-11-30 16:31 -------
Subject: Re:  time() returns incorrect value when given bad address

> time is marked with E, i.e. not returning error (which I'd say matches
> POSIX which doesn't define any errors for time).  By passing an invalid
> address to the function you reach undefined behaviour territory and all
> answers are fine in that case.
 
Hi Jakub

Thanks for your quick reply.

POSIX does not define any errno values for time(), but nevertheless 
says:

    Upon successful completion, time( ) shall return the value of 
    time. Otherwise, (time_t)−1 shall be returned.
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In my book, that means that time() should reasonably return -1
here.

The POSIX.1 "No errors are defined" means

    that error values returned by a function or stored into a 
    variable accessed through the symbol errno, if any, depend 
    on the implementation.

This does not (in my reading) mean that no error indication 
(i.e., -1 in this case) should be returned.

Note also that glibc is thwarting the underlying system call, which
does actually return -1 for this case (as my program demonstrates).

Cheers,

Michael



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http://sourceware.org/bugzilla/show_bug.cgi?id=1952

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