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Re: Thread safety of cout
On Fri, Oct 08, 2004 at 01:43:19AM +0200, Paolo Carlini wrote:
> >I would expect any program that uses cout in more than one thread,
> >without locking, to fail in random ways. A deadlock or crash means
> >you got lucky, because by the specs in that case it's allowed to
> >erase your disk and impregnate your sister.
>
> Something that I still don't grasp completely is the difference between
> fwrite / fwrite_unlocked and fflush / fflush_unlocked: the (glibc (*))
> specs don't seem to imply that the first two, respectively, take a
> lock?!? In that case, I would exclude at least pregnancy... ;)
Probably the POSIX people who (rashly) chose to ihave putc() and getc()
take a lock by default felt that special optimized versions of fwrite()
and fflush() were not necessary, because they would not be called
frequently enough for the locking overhead to matter. I would imagine
further that the glibc people added the "_unlocked" versions for
what they thought of as completeness.
Nathan Myers
ncm@cantrip.org